A Watershed Protection Plan for the
Public Utilities Company
of Heredia, Costa Rica
BSE 4126 Comprehensive Design Project
Final Report
February 9, 2016
Purpose: The purpose of this report is to present the final design for a watershed protection plan
to reduce erosion and sedimentation in the Rio Segundo and Rio Tibas watersheds in Heredia,
Costa Rica. This report includes an introduction to the problem, the background of the public
utilities company’s program, a discussion of the site visit, a literature review, alternative designs
considered, and a final design including a cost analysis.
Team Name:
Costa Rica
Group Members:
William Brown
Matthew O’Malley
Whitney Thomas
Client:
Public Utilities Company of Heredia S.A., Costa Rica:
Luis Gámez, Director of Environmental Management
Advisor:
Dr. Theo Dillaha
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Executive Summary: A Watershed Protection Plan for the Public Utilities Company of Heredia, Costa Rica
The Public Utilities Company of Heredia S.A. charges all customers a green fee in order to
pay land owners in the Heredia watershed to keep their lands forested or to reforest existing crop
land. Currently any land owner that wishes to take part in the program may enter into a contract
and all of these participants receive the same stipend of 45,000 colones/ha/yr for reforestation or
47,720 colones/ha/yr to maintain forest. The company would like to distribute funds based on
the amount of erosion and resulting total suspended solids each land parcel contributes. The goal
of this study is to identify the land areas that contribute the most to erosion and total suspended
solids in the Rio Tibas and Rio Segundo Sub-Watersheds of the Heredia Basin and determine the
BMP options that will help lower TSS to a monthly flow weighted average of 10 mg/L in each of
the sub-watersheds.
The majority of this project included designing a GIS program that delineated and ranked the
areas of the Rio Tibas and Rio Segundo watersheds in terms of erosion potential (and thus
sedimentation potential). The Universal Soil Loss Equation (USLE) was used with factors
derived from various case studies located in similar tropical environments. The results of this
analysis provided the first deliverable: GIS maps of critical land parcels within the targeted
watersheds. These maps showed that the primary factor contributing to high annual soil loss was
the cover factor derived from the land uses. The land uses that were the largest source of erosion
were permanent crop areas and urban areas that were primarily in areas of 0-15% slope.
The focus of this project is primarily on agricultural best management practices (BMPs) so
the urban areas were ignored in order to simplify this project. However, a second deliverable
addresses urban erosion sources: a portfolio of urban BMP handbooks, case studies, and water
quality monitoring guides that are being provided to the client.
The permanent crop area erosion was addressed by changing the cover factor of the
permanent crop area from 0.38 to 0.07 on the assumption that the best management practices that
we chose were 75% efficient and taking into account the other previous land cover factors. The
result was that all of the high and medium erosion areas in the Rio Segundo watershed were
reduced to low erosion and the medium erosion areas in the Rio Tibas watershed were reduced to
low erosion (disregarding urban areas). One assumption in accordance with the watershed
protection plan was that all permanent crop areas in the watersheds would install and maintain
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vegetation filter strips and/or practice intercropping. This assumption is liberal and would result
in a larger change in erosion ranking than in reality. However, this may be offset with the use of
a conservative P factor which was set to 1 for up and down the slope farming as there was no
spatial information obtained otherwise.
The BMPs were chosen after thorough research and comparison through a decision matrix.
The main criteria the decision matrix was used for was TSS removal, cost, maintenance, and the
area needed for construction To weight each constraint, the team talked with Mr. Gamez who
expressed that the main goal of the BMP was to reduce TSS, and secondarily to keep the cost to
a minimum. To determine which BMP was the best choice for the watersheds, each BMP was
ranked in terms of each constraint. Though many types of practices were researched and
documented in the literature review, only five were assessed in the design matrix: Retention
basin, extended detention basin, enhanced extended detention basin, vegetative filter strip, and
intercropping. The vegetative filter strip and the intercropping became the most applicable
BMPs when analyzed in terms of limited cost, less area required, and fairly large TSS removal.
Suggested landowner payment amounts were made for reforestation, maintaining forest,
vegetative filter strips, intercropping, and contour strip cropping based on the erosion ranking the
land is in and the cost of the particular practice being implemented. A cost analysis was done to
determine how much it would cost to implement a vegetative filter strip or intercropping for a 10
year contract. It was determined that it costs about $325/ac to install and maintain a filter strip
for 10 years. Similar analyses were done were done with the other BMPs. The cost as well as
the erosion ranking and relative amount of the watershed were used to determine landowner
payments. The results indicate that areas of high erosion should receive 150% of the current
stipend, medium erosion should receive 100% of the current stipend, and low areas receive 75%
of the current stipend. The suggested BMP landowner payments were also divided based on land
classification and price of implementation.
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Table of Contents: A Watershed Protection Plan for the Public Utilities Company of Heredia, Costa Rica
Executive Summary: ..................................................................................................................................... 2
Table of Contents .......................................................................................................................................... 4
Title: .............................................................................................................................................................. 7
Problem Statement ........................................................................................................................................ 7
Background Situation: .................................................................................................................................. 7
Connection to Contemporary Issues: ............................................................................................................ 7
Scope of Work: ............................................................................................................................................. 7
Objectives ............................................................................................................................................. 7
Deliverables .......................................................................................................................................... 8
Design Criteria: ............................................................................................................................................. 8
Design Constraints: ....................................................................................................................................... 8
Literature Review: ........................................................................................................................................ 9
Background on Costa Rica: ...................................................................................................................... 9
Problem Background: ............................................................................................................................. 11
Water Quality Management Background: .............................................................................................. 12
Environmental Laws: .............................................................................................................................. 13
Safety and Regulatory Considerations: ................................................................................................... 14
Costa Rican Regulations ......................................................................................................................... 15
Costa Rica Site Visit: .................................................................................................................................. 17
Preliminary/Alternative Designs: ................................................................................................................ 26
Geographic Information System Data Layers:........................................................................................ 26
Best Management Practices: ................................................................................................................... 28
Sediment Forebay ............................................................................................................................... 28
Retention Basin ................................................................................................................................... 29
Extended Detention Basin................................................................................................................... 30
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Enhanced Extended Detention Basin .................................................................................................. 31
Constructed Wetland ........................................................................................................................... 32
Bioretention Basin .............................................................................................................................. 33
Vegetated Filter Strip .......................................................................................................................... 34
Manure Storage ................................................................................................................................... 36
Fencing Cattle ..................................................................................................................................... 36
Concrete Grid Pavement ..................................................................................................................... 37
Grassed Swales ................................................................................................................................... 38
Intercropping ....................................................................................................................................... 39
Analysis: ..................................................................................................................................................... 40
BMP Alternative Designs: ...................................................................................................................... 40
Project Design: ............................................................................................................................................ 42
Cost Analysis: ..................................................................................................................................... 53
Work Plan: .................................................................................................................................................. 55
First Semester...................................................................................................................................... 56
Project Timeline: ................................................................................................................................. 57
(Fall Semester) .................................................................................................................................... 57
Second Semester ................................................................................................................................. 57
Project Timeline: ................................................................................................................................. 58
(Spring Semester) ............................................................................................................................... 58
Summary and Conclusions ......................................................................................................................... 59
Reflections .................................................................................................................................................. 60
Resources .................................................................................................................................................... 62
Appendix A ................................................................................................................................................. 64
Skills Required ........................................................................................................................................ 64
Qualifications: ..................................................................................................................................... 64
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Required prerequisite courses: ............................................................................................................ 64
Required co-requisite courses: ............................................................................................................ 64
Recommended courses/knowledge: .................................................................................................... 64
Estimated Commitment from a 3-member student design team: ........................................................ 64
Skills that must be developed for a successful completion of this project:......................................... 64
Advisors: ............................................................................................................................................. 64
Client:.................................................................................................................................................. 64
Appendix B ................................................................................................................................................. 65
GIS Design flowchart ............................................................................................................................. 65
Supplemental Pamphlet .............................................................................................................................. 66
Urban BMP Case Studies........................................................................................................................ 67
Annotated Bibliography – Urban Best Management Practice Handbooks ............................................. 69
Water Sampling ...................................................................................................................................... 70
How to measure sediment in water ......................................................................................................... 71
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Title: A Watershed Protection Plan for the Public Utilities Company of Heredia, Costa Rica
Problem Statement: Environmental stewardship and watershed protection are goals of the
Public Utilities Company of Heredia, Costa Rica. Currently, it is unknown which land parcels
contribute most to water quality degradation within the Heredia watershed. As a consequence,
the locations of critical areas of erosion within the Rio Tibas and Rio Segundo sub-watersheds
need to be determined. The goal is to identify the land areas that most significantly contribute to
erosion and water sedimentation, and to design a watershed management plan that will provide
erosion control in these areas to meet water quality objectives in the most cost effective manner.
Background Situation: The Public Utilities Company of Heredia S.A. in Costa Rica
charges all customers a green fee that is used to pay land owners to help protect the watershed
that contributes to the drinking water of Heredia. Currently, they pay land owners in the
watershed to keep the land forested or to reforest existing pasture and cropland. It is unknown
whether the lands they are paying to protect have a significant effect on the water quality
downstream.
Connection to Contemporary Issues: In today’s world, natural resource conservation and
protection are a critical part of society’s and the environment’s health. In Costa Rica, a private
water utilities company has taken it upon itself to improve and protect the water quality in its
watershed by reducing erosion and pollutants that runs off into surface waters by implementing
best management practices. These practices encourage ecosystem health and biodiversity as well
as provide water resource protection. However, in order to implement these practices, time and
money are needed. The Public Utilities Company of Heredia, Costa Rica is implementing
payments for ecosystem services using a small tax on customer water bills to cover these
expenses.
Scope of Work:
Objectives for the design project are to:
1. Identify land parcels having the greatest impact on water quality.
2. Rank the land parcels according to their impact on water quality.
3. Identify prospective best management practices for the land parcels to meet water
quality objectives.
4. Conduct hydrologic analyses of land management alternatives using GIS.
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5. Develop watershed management plans that consider the economic costs of various
watershed management alternatives and recommend the most cost effective scenarios for
the client.
Deliverables:
1. GIS map of critical land parcels.
2. Annotated list of urban BMP sources, case studies, and water quality sampling
methodology for future work in the Procuencas project.
3. Recommended watershed management plan.
4. Economic analysis for implementation.
Design Criteria:
Design criteria quantify the goals of the design. The major criteria are that the total
suspended solids will be reduced to less than 10 NTU or a flow weighted mean monthly TSS
level of 10 mg/L in each watershed. Sediment loading analysis will be conducted using GIS
analysis with the universal soil loss equation (USLE) and L-THIA { What is L-THIA? Not
mentioned subsequently in report that I could find.}.
Design Constraints:
Design constraints are restrictions that are imposed on the project by both the site and client.
Major constraints will be cost, environmental conditions, and area required. The total cost of the
project, including maintenance, will be kept at a minimum to allow the Public Utilities Company
of Heredia to maximize the amount of land they can reforest through PES. Both watersheds in
the project are small, leading to potential land area issues where there may not be enough open
land to implement a certain BMP. Environmental conditions, such as soil types, land slopes, and
land use, can all have an effect on the type of BMP implemented. A determining factor in the
BMPs chosen will be the land slope. The slopes in the two sub watersheds range from 0 to
greater than 60 percent slope. The upper land area in both Rio Segundo and Rio Tibas
watersheds have a greater than 60 percent slope.
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Literature Review:
Background on Costa Rica:
Costa Rica is a country located in Central America to the south of Nicaragua and north of
Panama (Figure 1).
Figure 1. Location of Costa Rica in Central America (Graphic Maps)
It borders two large bodies of water, the Pacific Ocean on the west coast and the Caribbean
Sea on the east coast. Costa Rica has a suitable tropic climate for agriculture and provides fertile
volcanic soils and an abundance of rainfall at about 2500 mm of precipitation per year (Toucan
Guides)). The agricultural sector in Costa Rica has been declining in terms of importance over
the past 50 years. Even with this decline, it still accounts for 15 percent of the gross domestic
product and still employs over one-fifth of the labor force. Production of agriculture in Costa
Rica accounts for only 10 percent of the country’s total land area. The main crops that are grown
are coffee, bananas, and sugar. The production of bananas alone, accounts for more than one
percent of the total land in Costa Rica. The farmers who grow these crops, as well as other
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crops, are supported by the government though research, training, and technical assistance. If
the Public Utilities Company of Heredia, S.A. offers to pay farmers to convert their agriculture
land to forest, it could ultimately affect the overall economy of the country.
Heredia is one of Costa Rica’s seven provinces and is located in the northeastern part of
the country (Figure 2).
Figure 2. Location of Heredia within Costa Rica (Graphic Maps)
It consists of northern lowlands which are warm and humid, and cool and damp highlands.
The population of the Heredia province is about 125,000 people in an area of 2,657 km2. As
livestock agriculture has decreased, many abandoned pasture lands have taken their place in this
area. Many of the current ecosystem problems in the area are due to deforestation, urban growth,
and livestock agriculture runoff. The most common land use in the region is old pasture land
that has been converted to either permanent crop systems or abandoned. These problems affect
the water quality of the area and the resulting drinking water of the people of Heredia. The
watershed that feeds drinking water to Heredia consists of five sub-watersheds; Los Ciruelos,
Segundo, Bermudez, Tibas, and Para. The focus of this watershed management plan will
concentrate on the Rio Segundo and Rio Tibas watersheds, the location of which is shown in
Figure 3.
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Figure 3. Location of watersheds of interest (Gámez).
Problem Background:
Costa Rica loses about 860 million tons of top soil each year (Butler, 2006). Most of this soil
makes its way into surface waters, degrading the quality of the water and increasing the costs to
provide clean potable water. Costa Rica has a national Payment for Hydrological Environmental
Services (PES) program designed to improve water quality through watershed protection by
improving flow regulation, water filtration, erosion control and sedimentation, and maintaining
the hydrological functions provided by forests. The national program is funded by a tax on
gasoline, private companies, and sale of certifiable tradable offsets. It is administered by the
National Forestry Fund and implemented by the Ministry of Environment and Energy, private
consultants, and NGOs. The program pays landowners to reforest or preserve forested land in
order to improve or maintain water quality. Redondo-Brenes and Welsh (2006) assessed the
Public Services Enterprise of Heredia (ESPH) Procuencas PES program. The Procuencas project
underway by the Public Utilities Company of Heredia, Costa Rica is a smaller version run by a
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private institution, ESPH, which provides more payment to the beneficiaries in the region than
the national program. ESPH provides water, electricity, sewage services, and public lighting
within the province of Heredia.
The main objectives of the Procuencas program are to conserve and restore the watersheds
that ESPH uses to supply potable water to their customers and to improve surface water quality
within the watersheds. This is done by providing economic compensation to landowners who
voluntarily conserve or reforest their private lands. This ESPH program creates revenue by
taxing the water users an environmental fee. This environmental fee is used to implement best
management practices (BMPs) that increase water quality within the watershed. This program
was deemed to be a success by Redondo-Brenes and Welsh (2006) through the hydrological fee,
where 100% of the local residents receive potable water from ESPH and over 1000 hectares of
land are protected. Other companies are leaning towards these policies proving the program’s
business success. One weaknesses of the ESPH program is the objectives of the program were
not adequately communicated to the public. Other weaknesses include a revised delineation of
areas designated for well protection and more coordination and control across Costa Rican
institutions is needed (Redondo-Brenes and Welsh, 2006).
This program sets in place a new mechanism for the private business industry to promote
public-private partnerships in sustainable development. The national legislation placed a ban on
natural forest cutting and provided payment to the owner in exchange for the protection of forest
and the resulting ecosystem services: carbon sequestration, water resources, biodiversity, and
scenic values. This program is financially beneficial when the cost of protecting the water
supply, quality, and flow is lower than the cost of cleaning polluted waters. This strategy is based
on a social equity and the water user-pays-principle. This program should be considered in other
developing countries as an example of an achievable sustainable land use plan.
Water Quality Management Background:
In the report written by Pearce and Pearce (2001), many factors are analyzed to determine the
value of a forest ecosystem for a given area of land. The value of the ecosystem consists of both
the economic value and the environmental value. When the Public Utilities Company in Costa
Rica begins to reforest land it would be useful to know exactly what impacts reforestation has on
the environment and the economy. The report states that forests regulate local and global
climate, ameliorate weather events, regulate the hydrological cycle, protect watersheds and their
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vegetation, water flows and soils, and provide a vast store of genetic information much of which
has yet to be uncovered (Pearce and Pearce, 2001). All of these aspects illustrate how important
a good forest ecosystem can be to the environment and the economy.
The report compiled research by other groups to express the watershed protection values of
forest. Most of the numbers found were small when expressed on a per hectare basis, but if the
areas are large, the values could be substantial. Another factor that was studied was carbon
sequestration. A table within the report illustrates how much carbon can be stored and
sequestered for different land uses: forest, shifting agriculture, permanent agriculture, and
pasture. The data shows that if the land is in forest, the amount of carbon sequestered and stored
is much higher when compared to the other agriculture uses. Since worldwide carbon “trading”
is occurring, the amount of carbon sequestered in a forest in Costa Rica could affect the
economy. The value of sequestered carbon per acre in a tropical environment, like Costa Rica,
could be as high as $2,000/ha (Pearce and Pearce, 2001).
Overall, the report suggests that if forest land is present, the impact on the environment and
economy is quite large. For Costa Rica, it is quite evident that reforestation and forest
conservation is a right step into protecting their watersheds.
Environmental Laws:
Other constraints on the design of this watershed protection plan will exist in the form of
laws, regulations, and accepted standards. Since the area of environmental protection is in the
process of growing in Costa Rica, accepted standards and practices from the US will be
compared to those in law in Costa Rica. The laws of environmental protection in Costa Rica are
not enforced.
In the past, Costa Rica deforestation has been a problem due to the conversion of forest to
pasture lands to raise cattle. The attempts at animal production were abandoned and now there
are many areas that have abandoned pasture. Since these times, the Costa Rican government has
taken steps to reduce the erosion that occurs on these abandoned pasture lands as well as many of
the other environmental problems that occur. Several of the regulations that they have put in
place will be constraints that our watershed protection plan must follow (though these laws are
not strictly enforced).
The Forestry Law (World Research Institute, 2006) which was established in 1996 identifies
the services provided by natural forest systems and provides compensation to private forest
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owners for reforestation of their lands. It also is a way of the state showing its role in conserving
of the environment (World Research Institute, 2006; Redondo-Brenes and Welsh, 2006). This
law is important to our project in that it is the national PES program where we are dealing with a
smaller regional program. It provides the basic layout of this program and provides
supplemental funding for the Public Utilities Company of Heredia project.
The Wildlife Conservation Law (Department of Wildlife, 1995) provides definitions for
many of the terms used in natural resource management and gives the Department of Wildlife,
thru the Ministry of Environment and Energy the power to develop, define, and enforce
government guidelines for the best allocation and management of Costa Rica’s resources. In
particular it allows the General of Wildlife the responsibility to establish measures to conserve
and manage the flora and fauna of Costa Rica, to recommend building new wildlife refuges and
manage them, to “encourage the establishment of shelters for wildlife and hunting on private
farm property, and request the detention of people who invade buildings of the national wildlife
refuges” (Department of Wildlife, 1995). This law is pertinent to our design in enabling us to
use the language necessary for communicating our plans for conserving the watershed in any
publications we may need to write to the Costa Rican government. It also may be necessary to
work with the Department of Wildlife, concerning the plans for the current flora and fauna
within our watershed.
The General Health Law (Legislative Assembly of the Republic of Costa Rica, 1996), states
that the “health of the population is a public interest protected by the state.” This law was
created to ensure the health of the Costa Rican population by instating laws similar to the United
States governing actions of persons and entities that affect others health (Legislative Assembly
of the Republic of Costa Rica, 1996). This is a law that further supports the work being done to
further improve the water quality being served to the public via the Public Utilities Company of
Heredia.
Safety and Regulatory Considerations:
The development of a watershed management plan for Rio Segundo and Rio Tibas
watersheds in Heredia, Costa Rica requires communication as an important tool in designing,
building, and maintaining the Best Management Practices (BMPs) used to improve the water
quality. Since the plan is to be implemented in a country outside of the United States, it is
especially important to design and publish within accepted guidelines or standards. The
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American Society of Biological and Agriculture Engineers (ASABE) has established
terminology for soil and water engineering for use in all standards, technical journals, magazines,
textbooks, and bulletins pertaining to the field (ASAE S526.3, Sept2007). This standard will be
used in our documentation and communication during the entire process of design as well as in
any implementation that may be done. Another set of standards deals with uniform terminology
for rural waste management (ASAE S292.5, Feb2004). Agriculture accounts for almost 38 % of
the land use located over groundwaters in Heredia (Gamez). This standard is necessary in
describing any best management practices dealing with the dairy manure within the watersheds.
Though the Public Utilities Company of Heredia currently only implements reforestation,
other management practices need to be explored for the other land uses in the watershed. One of
the options includes water and sediment control basins that are used primarily in more urbanized
areas. A set of standards describes the planning, design, layout, construction, maintenance, and
safety aspects of water and sediment control basins that are accepted in the United States (ASAE
S442, Oct1986). These control basins are meant to be implemented to reduce gully erosion, trap
sediment, and improve downstream water quality. The Public Utilities Company of Heredia,
Costa Rica aims to reduce soil loss and sediment loading, which could be partially addressed
with control basins.
Another problem the utilities company wants to address is bacteria concentrations in runoff
from dairy farms in the region. One way to help address this problem is to implement manure
storage facilities. These facilities are designed to accumulate manure, wastewater, and runoff
from a given farm. After this accumulation occurs, the slurry must remain in the storage facility
for a period of time that allows it to become deemed “environmentally safe” to be deposited back
into the land. A set of established practice techniques published by the ASABE provides
recommendations for site choice, design, and construction of the above mentioned manure
storage units (ASABE EP464, Dec2006). These standards also include U.S. laws and
regulations involved with the implementation of such structures.
Costa Rican Regulations
The focus of regulations is on nutrient loading, total suspended solids, and bacteria loading
within the watersheds in question. Most of the water problems in the region stem from
agricultural runoff, and urban expansion. The federal regulations apply to all wastewater being
discharged into any surrounding water body. The main aspect of concern from the abandoned
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land is soil loss since much of the land is barren and not well covered. When looking at the
effluent from the dairy farms, the main concern is with bacteria loading and nutrient loading.
Many of the farms currently direct discharge into the surrounding water bodies, which poses a
problem to the water quality. The nutrients that are of greatest concern are nitrogen and
phosphorus. Since dairy manure contains greater amounts of nitrogen, it is going to be much
harder to manage this nutrient. The regulations state that the total nitrogen can not exceed 50
mg/L and that phosphorus levels cannot exceed 25 mg/L. {In what? receiving waters?} As
stated above many of these regulations are not followed and there is no agency to strictly enforce
these.
The water quality standards of Costa Rica can be compared to those of the United States,
specifically the water quality standards of Puerto Rica, which has a tropical climate. The
Commonwealth of Puerto Rico (2003) lists the following criteria for surface waters that are to be
used as a raw intake for a public water supply; nitrate plus nitrate less than 10,000 µg/l {I believe
that this is about 1000 times to high. The limit is usually closer to 10 mg/L}, total phosphorus of
one ppm or demonstration that the current level does not contribute to eutrophication, turbidity
less than 10 NTU, and geometric mean of 5 water samples for coliform to be less than 10,000
total colonies/100 ml, less than 2,000 fecal colonies/100 ml with not more than twenty percent of
the samples having more than 4,000 fecal colonies/100 ml. This comparison is necessary
because the water quality standards of Costa Rica are not enforced {What does not enforced
mean in this case?}, meaning that no penalties are invoked on anyone who contributes heavily to
water quality degradation.
The safety regulations that are relevant to this design project involve our site visit to Costa
Rica and the water quality design criteria that will insure public health. For safety purposes, the
requirements to enter and exit the country are quite stringent. For entry into Costa Rica, United
States citizens must present valid passports that will not expire for at least thirty days after
arrival, and a roundtrip/outbound ticket. Once entry into the country has been permitted, one is
allowed to stay for up to ninety days without having to request for a time extension. Even
though the country is stable in regards to the government, visitors may experience the effects of
civil disturbances such as work stoppages and strikes. These disturbances usually just create an
inconvenience for visitors and do not impose on personal safety. Many U.S. tourists are targets
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for thieves looking for cash, jewelry, and expensive belongings. Tourists are advised to avoid
areas with high percentage of bars and nightclubs, avoid driving at night and in rural areas, avoid
deserted properties and undeveloped land. This is important to the site visit as it is occurring
partially to take photos and water samples of and from the different land use types within the
watersheds. Tourists are also encouraged to carry photocopies of the passport data page and
Costa Rican entry stamp while traveling within the country, and leave the original passport in a
hotel safe or other secure place. It is also recommended to use licensed taxis (red with yellow
triangles), and if using a bus to keep all items on your person. It is not recommended to rent a
car. If any crime does occur, the Tourist Police is the agency to contact, who will help to report
the crime (when language barriers exist) (U.S. Department of State, 2008).
Costa Rica Site Visit:
A site visit occurred to the city of Heredia from January 7th – January 14th, 2009. The main
purpose of the trip was to gain a better understanding of the area and the culture as a whole, so as
to understand constraints that may not be directly quantified. While in Heredia, Rio Segundo
and Rio Tibas sub-watersheds were visited and professionals from the National University gave
presentations on the current water quality status.
Mr. Luis Gámez, the lead water quality consultant for the Public Utilities Company of
Heredia guided the site visits within the watersheds. The first two days consisted of traveling to
the upper sections of the watersheds to view the problem areas in the landscape. Some of the
areas that had previously been pasture land had been reforested through the Public Utilities
program and were showing signs of succession (Figure and Figure 5).
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Figure 4. Pre-reforestation in Rio Tibas. (Luis Gámez)
Figure 5. Same area five years after reforestation induced. (Whitney Thomas)
This succession shows that the reforestation efforts that were induced by the Public Utilities
Company of Heredia have been successful thus far and the vegetation will likely continue to
mature so that the area will eventually reach its climax stage. This reforestation is important in
maintaining soil integrity and optimum water quality in the upper regions of the watersheds. The
major surface water inlets that were currently being used to supply a portion of the drinking
water for the city were located in the upper regions of Rio Tibas and Rio Segundo watersheds
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(Figure and Figure respectively).
Figure 6. Rio Tibas surface water inlet with engineered sediment barriers. (Matthew
O’Malley)
To protect the Rio Tibas inlet and reduce the amount of sediment entering the system, the
area behind the dam in Figure 10 above had been excavated and replaced with large rocks to
slow the flow and increase the chances of sedimentation of suspended solids. This surface inlet
is the oldest one that they own and it is still currently in use; it collects 20 l/s. The in-stream
sediment BMP was constructed before the Public Utilities Company of Heredia owned this area.
Mr. Gamez says that it is not a good BMP for this system as it collects too much sediment too
close to the inlet; they often have to remove particles in order to fulfill the water collection
volume needed. This surface inlet is the only one that had this BMP in use and was also known
to be the inlet with the largest quantity of sediment problems. A different structure of surface
inlet was used in the Rio Segundo watershed which can be seen in Figure 7 below.
19
.
Figure 7. Rio Segundo surface water inlet. (Matthew O’Malley)
This inlet had a larger pond behind the damn and used cement blocks at the bottom of the fall
to disperse energy and avoid stream bed erosion. This type of construction better suited the
purpose of collecting water as the dam allowed for ponding and thus deposition of particles
before the inlet. This inlet collects 40 l/s of water.
The amount of suspended solids within each river is dependent upon the land area in the
watershed. This site visit allowed for the group’s better understanding of the topography and
land cover of the watersheds. Many issues that otherwise would have been overlooked for the
design of a watershed protection plan were discovered by visiting the watersheds. One major
issue is the lack of enforcement revolving around land clearing on private properties (Figure 1).
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Figure 1. Example of land clearing. (William Brown) {2 figure 1’s}
People who may or may not own the land, clear cut land that they assume to be abandoned to
allow their cattle to graze. This can become significant in terms of erosion and resulting stream
total suspended solids when this land clearing occurs on slopes with slopes over 15% as almost
all land was seen to be in these upper reaches of the watersheds. Another issue throughout the
watersheds was that major erosion was occurring along the dirt road banks.
These facts must be considered when developing a watershed protection plan as part of a
whole understanding of the watershed and the community.
While touring the watersheds, Mr. Gámez emphasized the fact that the public utility
company had no efficient system to measure sediment loading in the two rivers that could be
used to quantify the reforestation benefits. Advice on a sediment monitoring program was
requested. This information would be used (if implemented) to measure how much erosion and
water sedimentation is being controlled by the reforestation program. This request has altered
the deliverables slightly since this was not part of the initial problem statement, however to meet
the clients needs this information is included in the supplemental pamphlet that will be sent to
Mr. Gamez with this studies results.
21
About midway through the visit, Dr. Coot, a professor who has been doing significant water
quality research in the upper portions of the watersheds presented her results. She demonstrated
a public water quality program that is currently being promoted by the university that allows
individual land owners and concerned community members to monitor water quality on their
land using equipment that is locally available. Samples are collected and tested every fifteen
days. The data taken by these land owners included dissolved oxygen content, turbidity, pH, and
phosphorus levels. A visit to the Rio Segundo water inlet to take water quality samples with the
tools available to the landowners and the help from Dr. Coto resulted in an example of how their
stream monitoring program works. Figure 9 shows the method for collecting a water sample.
Figure 9. Taking water samples at Rio Segundo inlet. (Whitney Thomas)
The team then used the water sample to test for turbidity, dissolved oxygen, and
phosphorous levels (Figure 10).
22
Figure 10. Testing Rio Segundo water samples for turbidity and other water quality
indicators. (Whitney Thomas)
To test for turbidity, sample water is added to a bottle and chemical indicator drops are
mixed in. The sample is then capped and shaken to distribute the indicator, and let to rest. After
5 minutes the sample is compared to a set of turbidity examples ranging from 200 NTU to 0
NTU (Figure 11).
23
Figure 11. Set of turbidity examples used in community outreach stream monitoring kits
implemented by Professor Coto and the Universidad Nacional. (Whitney Thomas)
The next test done on the water sample was to determine the amount of dissolved oxygen
in the water. Sample water is added to a container with a precipitant and shaken for 30 seconds.
Once the precipitant formed and settled on the bottom of the bottle, a titration was done;
indicator drops were added to the container until the water became clear (Figure 12).
Figure 12. Professor Coto’s test for dissolved oxygen in water samples. (Whitney Thomas)
For the phosphorous test, phenolphthalein drops are added to a sample of water and
compared to a set of examples (Figure 13).
24
Figure 13. Phosphorous test comparison bottles for monitoring volunteers. (Whitney
Thomas)
Additionally the university tests the sediments four times a year, twice in the dry season and
twice in the rainy season. Samples are taken at 3 points in the stream, in the middle and on either
bank, approximately ten centimeters deep. The sample is taken using PVC pipes of 10 cm of
diameter and 15 cm of large, covered inside with plastic paper. Then each pipe is stored in a
plastic bag sealed off to the air. Once back at the laboratory the sediments are dried for a week
at ambient temperature, in a dark place at 20-60% humidity, over black plastic bags, or using a
stove at 40ºC. Once the sediments are dried, they are dispersed with a glass or wood stick; and
after that, are sifted in a 2 mm sieve, to eliminate roots residues, pieces of rock, and other
materials different than soil. If there is a great quantity of sediments, is necessary to select a
representative sample to be used in the analysis.
The data that was obtained from the water samples will be used in conjunction with the GPS
points that were taken to evaluate the current status of the Segundo River. Even though the
Nacional University Water Quality monitoring program obtains data from the watersheds, the
data is not very precise. The program is mainly set up to get rough water quality information
25
from the volunteers that monitor the rivers, while sending out professionals only four times a
year or when significant changes in data occurs. Professor Coto stated that the data from the
volunteers were looked at regularly and if some values seemed high, a trained technician would
be sent out for follow-up testing. This methodology saves the university money while still
monitoring the watersheds water quality.
Mr. Kenneth Masís Nuñez completed his graduate school thesis with the geography
department at the National University on GIS analysis of the Heredia watershed. He presented
some of the GIS layers he had developed and what each one contained. Unfortunately, his
English was not fluent and it was difficult to work through any questions. However, it is his data
layers that we are primarily working with for the analysis of the Rio Segundo and Rio Tibas
watersheds. Mr. Nuñez is now currently working with the Costa Rican Institute of Sewage.
Overall, the trip was very useful for the project. A better understanding of the watershed
protection problem was had by visiting the sites and being able to physically observe the
watersheds and experience the culture of Costa Rica. Part of the physical environment that we
hadn’t considered previously was occasional earthquakes. In fact, a major earthquake occurred
in an area near the target watersheds while the team was in the field. The earthquake was a 6.2
on the Richter scale. It was a very educational experience to see how the natives dealt with that
situation, as well as seeing the potential issues with implementing structural BMPs in an area
where the land can move and damage the BMP.
Preliminary/Alternative Designs:
Geographic Information System Data Layers:
In order to successfully analyze the erosion and stream sediment occurring in the Rio Tibas
and Rio Segundo watersheds, ArcGIS was used to compile the characteristics of the watersheds
needed for data analysis. The Universal Soil Loss Equation (USLE) was used in conjunction
with ArcMap version 9.3 to determine the average annual soil loss of each parcel of land. The
GIS layers pertinent to the USLE include precipitation data, soil data, elevation data, land use,
land cover, and land management in the area in question.
Soil data was downloaded from the ISRIC World Soil Information site. This organization
worked with the United Nations Environmental Program (UNEP), the Food and Agricultural
Organization of the United Nations (FAO), and the International Potato Centre (CIP) to compile
26
this file. The data was made in 1998 at a 1:5 million scale since the layer includes soil data for
all of South and Central America. The data was downloaded in an .E00 form which did not open
in ArcGIS automatically. This required the downloading of the program Import71 in order to
convert the .E00 files to .SHP files to view them correctly. Since this layer has a very large
scale, it is not as detailed as one focused on the soil in just Costa Rica. The information from the
ISRIC soil data layer was used in comparison to the soil data layer obtained from Mr. Kenneth
Nunez in Costa Rica to solidify the validity of Mr. Nunez’s soil types in Heredia.
Precipitation data was found in report that professors from Smith College in Northampton,
Massachusetts submitted to Monteverde Institute in Costa Rica. Monteverde, Costa Rica is just
northwest of the watersheds of Heredia. This 2006 report on precipitation gives the mean annual
precipitation throughout Costa Rica to be 2710 mm. This is an average between 1973 through
2006. Because the Rio Tibas and Rio Segundo watersheds are fairly small, an assumption will
be made that the rainfall within the watersheds is equally dispersed and equivalent, unless more
detailed data can be found.
Elevation, land cover, and Central American boundaries were all found in the same location.
The programs of Proyecto Ambiental Regional de Centro America (PROARCA) and Central
America Protected Areas Systems (CAPAS) produced downloadable data for the vegetation,
land cover, and conservation status of all of Central America. The other organizations involved
in creating this data were Central American Commission on Environment and Development
(CCAD), the United States Agency for International Development (USAID), the International
Resources Group, Ltd. (IRG), the Nature Conservancy (TNC), The Center for International Earth
Science Information Network (CIESIN) and Winrock International (WI). This data was
compiled in 1998 and contains 17 vegetation types. The elevation data has a one kilometer
resolution and the scale of the vegetation/land cover layer is 1:2 million. The boundaries have a
scale of 1:1 million. The scale of these layers may generalize areas more than would be liked.
A solution to the large scales of all of the above layers was a recent compilation of data
layers provided by the client, Mr. Luis Gámez of the Public Utilities Company of Costa Rica.
The data contains layers containing all of the pertinent information for analysis of the watersheds
that is focused solely on the Heredia watersheds. It also delineates the sub-watersheds that are
critical to this investigation. For these reasons this compilation of layers was used for the USLE
27
analysis in GIS. The layers found through the research above were used for comparison with the
layers from Mr. Gámez for validation.
Best Management Practices:
In order to improve runoff and ground water quality, a variety of best management practices
(BMPs) need to be considered to decrease erosion and thus, nutrient, sediment, and bacteria
loading. The research done on best management practices indicated the following alternative
designs to be better suited for sediment reduction. The fact that most of the research done on the
effectiveness of these BMP’s have been in temperate environments must be taken into
consideration when determining the optimal BMP(s) for a tropical watershed protection plan.
Sediment Forebay
Sediment forbays are basins that accept water into the BMP area and pre-treat the water for
sediment (VA Dept. of Conservation and Recreation 1999). This component is usually used in
conjuncture with other BMPs at the inflow point. According to the Virginia Stormwater
Handbook (1999) its main use is to dissipate flow energy of the incoming stormwater and settle
out particulates in an isolated area of the BMP area. This allows for less maintenance problems
as the sediment is located in a small area instead of the entire retention basin, detention basin, or
constructed wetland and faster sediment accumulation. Due to the rapid sediment accumulation,
sediment forbays should be cleaned out every three to five years. Figure 14 shows a typical
sediment forebay in series with a retention basin. All of the removal efficiencies for the other
28
BMPs assume that a sediment forebay is included in the design.
Figure 14. Typical sediment forebay in series with retention pond (VA Dept. of
Conservation and Recreation 1999).
Retention Basin
Retention basins are basins that utilize a permanent pool of water to remove pollutants and
slow the release of stormwater into the watershed to reduce flooding (VA Dept. of Conservation
and Recreation 1999). According to the Virginia Stormwater Management Handbook (1999)
retention basins have a high removal rate of particulate and soluble pollutants. Pollutants are
removed by gravitational settling, biological uptake and decomposition at efficiency rates of 5090% total sediments, 40-80% total phosphorus, and 30-90% soluble nutrients. A typical
retention basin plan is shown in Figure 15.
29
Figure 15. Typical plan of a retention basin facility (VA Dept. of Conservation and
Recreation 1999).
Note the use of a sediment forebay located up flow from the retention basin. Retention
basins are most economical on a regional or watershed size treatment area, since cost per acre
treated diminishes as the facility becomes larger. The minimum drainage area to support a
retention basin is ten acres (VA Dept. of Conservation and Recreation 1999).
Extended Detention Basin
Extended detention basins are basins that remove pollutants and helps control downstream
flooding by providing storage area and time for pollutants to settle (VA Dept. of Conservation
and Recreation 1999). An Extended detention basin is typically dry during non-rainfall time
periods which is the difference between it and a retention basin. According to the Virgin Islands
Environmental Protection Handbook (2002) up to 90% of the particulate pollutants can be
removed by an extended detention basin while only a slight amount of the soluble nutrients are
30
removed. A typical extended detention basin is shown in Figure16; note again the use of a
sediment forebay at the BMP complex inflow.
Figure 16. Typical extended detention pond design (VI Environmental Protection
Handbook 2002).
Extended detention basins are most cost effective when implemented on a watershed wide
scale (VA Dept. of Conservation and Recreation 1999).
Enhanced Extended Detention Basin
Enhanced extended detention basins build on extended detention basins by including a
shallow marsh at the bottom of the basin (VA Dept. of Conservation and Recreation 1999).
According to the Virginia Stormwater Management Handbook (1999) this marsh gives the
enhanced extended detention basin a higher efficiency by removing pollutants by plant uptake,
absorption, filtration and decomposition in addition to gravitational settling. An example of an
enhanced extended detention basin is shown in Figure 17; once more a sediment forebay is used
as a first step treatment.
31
Figure 17. Typical enhanced extended detention pond design (VA Dept. of Conservation
and Recreation 1999).
Constructed Wetland
Constructed wetlands are manmade shallow pools that create growing conditions for
emergent and aquatic vegetation to enhance the water quality (VA Dept. of Conservation and
Recreation 1999). According to the Virginia Stormwater Management Handbook (1999) high
removal rates of particulates and nutrients are accomplished through settling, plant uptake,
absorption, filtration and decomposition. Disadvantages of constructed wetlands include the need
of a steady water source and an increase of mosquitoes if stagnant areas form (VI Environmental
Protection Handbook 2002). Due to the tropical wet dry seasons, these disadvantages could lead
to an exclusion of constructed wetlands from use in Costa Rica. An example of a constructed
wetland design can be seen in Figure 18.
32
Figure 2. Example of a constructed wetland design (VA Dept. of Conservation and
Recreation 1999).
In most cases the minimum size should be ten acres provided an adequate base flow is
available to support the vegetation (VA Dept. of Conservation and Recreation 1999).
Bioretention Basin
Bioretention basins, also referred to as rain gardens, are shallow basins containing a sand
bed, soil, surface mulch, and plants (VA Dept. of Conservation and Recreation 1999). Water
quality is improved through filtration by the content of the basin; soil, sand, mulch, and root zone
as well as microbial processes, ion exchange, and decomposition. This type of BMP allows
stormwater to enter the groundwater system, where Heredia obtains 80% of their drinking water.
When placed in an area that receives a large amount of sediment, this BMP quickly becomes
33
clogged, rendering it useless until it is reconstructed (VA Dept. of Conservation and Recreation
1999).
Figure 3 {Skipped several figure numbers. Do not bold as earlier captions not bolded}.
Example of a bioretention basin design (VA Dept. of Conservation and Recreation 1999).
Vegetated Filter Strip
Vegetated filter strips are densely vegetated strips of land that slow and infiltrate overland
sheet flow (VA Dept. of Conservation and Recreation 1999). According to the Virginia
Stormwater Management Handbook (1999) only 10% of nutrients are removed by a vegetated
filter strip through filtration sediment deposition and infiltration. An example of this BMP is
shown in Figure 20.
34
Figure 4. Vegetated filter strip design (VA Dept. of Conservation and Recreation 1999).
Plants selected for filter strips should have dense top-growth to provide good, uniform soil cover,
and a fibrous root system for stability. In addition, the type of vegetation selected should be
adapted to local soil and climatic conditions, and have good regret following dormancy and
cutting. Grasses have been found to be more effective than broadleaf plants for erosion control
since they form a dense sod, have a fibrous root system and provide a more complete ground
cover. Sod forming grasses are preferred over bunchgrasses since they provide more uniform
ground cover. Bunchgrasses should only be used in combination with other plant species.
Legumes may be seeded along with grasses to improve soil fertility and forage quality, but they
are not as effective as grasses in filtering sediment. Legume and grass species with different
growth habits should be selected so that competition between species is reduced.
35
Manure Storage
Manure storage ponds, pits, and tanks are options that can be utilized in the treatment of
waste materials that come from dairy farms. There are three main types of storage options:
under-floor pits, outside storage tanks or ponds, and treatment lagoons. The first two options are
mainly for storage of the manure for a short period of time before it is spread on surrounding
fields as liquid fertilizer. The lagoon is used to hold the manure for extended periods of time so
microbes and other biological activity can break it down. All of these structures accumulate
collected wastes and allow the waste management system operator to move away from a “daily
scrape (collect) and haul” situation. This reduces time and labor needed for final disposition,
either land application or off-farm “value-added” processing, of these manure accumulations. In
general, the earthen pits cost substantial amount less than steel or concrete structures (Tyson, and
Mukhtar, 2008).
Contrasting storage and storage with treatment, a manure containment structure which is
emptied at the end of the storage period is a storage structure. Generally, when agitation is used
to put settled or floating solids into suspension before pumping out the effluent, or the slurry, the
structure is being operated as storage. A lagoon differs in that it has both a storage volume and a
permanent pool for residual treatment volume. By having this permanent pool, there is a
bacterial seed bed that is always present providing continual bacterial action. This permanent
pool is not considered in the design of a structure used for storage alone. Essentially whatever
goes into a properly managed storage structure is what is pumped out. A lagoon, however, is
designed to promote decomposition of organic matter entering the lagoon. Since the lagoon
holds the waste for extended periods of time to promote biological activity, they are designed to
be much larger. This required space could prove to be a problem on small farms and other land
parcels that do not have much land area. These lagoons must also be emptied once every ten
years. The material being removed from the lagoon is digested solids that have accumulated
over several years. This emptying is done to restore the residual treatment volume of the lagoon
(Tyson, Mukhtar, 2008).
Fencing Cattle
A cheap and effective agriculture related BMP includes fencing cattle out of surrounding
streams. By fencing the cattle out of the stream, a buffer area on both sides of the stream can be
formed. This buffer area helps reduce erosion as well as sediment loading to the water body. A
36
group of researchers studied the effects of stream bank fencing in a small watershed in Lancaster
County, Pennsylvania.
The study indicated that a small buffer width along a stream in pasture land can have a
positive influence on surface-water quality, benthic macroinvertebrates, and near-stream shallow
ground-water quality. Certain sections of the stream were fenced while others were not. Results
from water samples from each area were then compared to each other to find any correlation to
the fencing with improved water quality. Stream bank fencing resulted in decreases in certain
forms of nitrogen, total phosphorus, and suspended sediment concentrations at the outlet of the
treatment basin. However, dissolved phosphorus concentrations increased. Nutrient management,
in conjunction with stream bank fencing, was partially effective in controlling nutrient loadings
to streams in this agricultural setting (Mayer, 2005).
Implementing streambank fencing can be very beneficial to the water quality surrounding a
dairy farm. The cheapest type of fence that can be used is an electrified polywire fence. From
an economic analysis conducted by Iowa State University, it was found that this type of fence
only cost $0.18 per foot. For the purpose of fencing cattle from a stream, a high tensile
electrified fence would be the best option. This type of fence cost around $0.70 per foot. The
majority of this cost is associated with labor cost. A high tensile fence also requires
approximately $121 per year to maintain the fence. These fences also have an estimated useful
life of 25 years (Mayer, 2005).
Concrete Grid Pavement
Concrete grid pavement is an alternative to the conventional pavement that promotes greater
infiltration. The concrete is usually poured in to a mold that has dispersed holes throughout in
which gravel, sand, or grass can be placed. The voids in the concrete promote infiltration of
storm water.
The subsoil below the system is used to absorb and strain the stormwater flowing into the
voids. The microbes in the subsoil also help with decomposition of the pollutants. The material
used to fill the voids in the concrete traps the particulate matter that is in the water. The main
goal of this alternative concrete is to reduce surface water pollutants and sediment is runoff from
parking lots and other impervious surfaces. The expected removal efficiency of a well-designed,
well-maintained concrete grid pavement is projected to be 95% for total suspended solids, 60%
for total phosphorus, and 88% for total nitrogen. The grid pavement performs exceptionally well
37
for immediate results. But overtime the sediment will clog the system and eventually lower the
performance capabilities.
The concrete grid pavement can be used on driveways and other low traffic roads. The soils
in Costa Rica have a permeable structure which will benefit this BMP. Depending on the
location in which the BMP is implemented, the slope could pose a problem, because the grid
pavement works best in low slope areas. Another potential problem is high levels of sediment
input. High levels of sediment could clog the BMP very easily and shorten its life span greatly.
Since the voids in the pavement are prone to clogging, the site must be cleaned out regularly. If
the system becomes clogged it will be very pricey because the base material (grass, sand, gravel)
and the underlying subsoil will have to be replaced. Another problem with the pavement is
retrofitting because if the soil has previously been altered or displaced, it will be hard to replace
the existing pavement because if compaction. The soil structure may not support this type of
feature. The biggest problem with implementing this BMP in Costa Rica is the amount of time
and money to maintain the pavement to ensure it excels in terms of performance. The overall
cost of the system will be very small if utilized in small areas and if it is maintained properly.
Grassed Swales
Grassed swales are earthen systems in which pollutants are removed from the surface runoff
by filtration through grass and infiltration through soil. The swale should have a relatively wide
bottom to promote even flow through the grass to avoid channelization. Some grassed swales
include a check dam (i.e. railroad tie) to increase storage which in turns promotes greater settling
of pollutants.
A conventional grassed swale design, in the past, has shown to have mixed results. The
expected removal efficiency of a well-designed, well-maintained conventional swale is projected
to be 70% for total suspended solids, 30% for total phosphorus, 25% for total nitrogen, and 50 to
90% for various trace metals. No data are available to demonstrate the effects of the added
check dam; but the detention capability they add is projected to be quite useful.
The grassed swales are very effective in small, single family subdivisions. In the watersheds
in question the swales will be used in the suburban areas outside of the main cities. Since the
soil is Costa Rica is very karst, this type of BMP would be ideal in most situations because
infiltration is a key factor in the BMPs effectiveness. Grassed swales can be used in areas where
the climate and soil permits establishment and growth of dense vegetation. The topography of
38
the watersheds needs to be considered to ensure the swale is placed in the areas with very little
slope. If the slope is too great, the flow will be too quick and infiltration will decrease greatly.
Retrofitting current grass channels is a very feasible option in Costa Rica. If a grass channel is
already present, the implementation of a check dam will greatly increase removal of most
pollutants. The maintenance for these systems is very low. With little mowing the grass can be
kept at its optimal height (minimum of 15.24 cm). With proper maintenance the swales can last
an indefinite period of time.
Intercropping {I believe that we had discussed strip cropping - not intercropping as a potential
BMP.}
One of the two BMPs that will be implemented in the watershed protection plan is
intercropping. Intercropping is the agriculture practice of cultivating two different crops in the
same space at the same time (Andrews & Kassam, 1976). The traditional practice of
intercropping mainly occurs in developing countries because of the abundance of manual labor.
New adapted versions of this system are beginning to emerge in the US and Europe that are
utilizing modern equipment. An intercropping system may benefit crop yield and at the same
time control some types of pest. For this design project, the intercropping system will be used to
help prevent soil loss and sediment loading into nearby streams within the watershed. If used in
place of row cropping in the agriculture regions of the watershed, the intercropping system will
keep the bare soil covered throughout the growing season. By keeping plants roots in this bare
soil, runoff velocity will be decreased and the opportunity for sediment deposition will be greatly
increased. There are many plant combinations currently being used to help with these
environmental problems.
One of the main ways intercropping is utilized, is by growing a grain along with a legume
plant. This can be wheat with cow peas or a more commonly utilized combination of maize with
some type of bean. Some specific examples of intercropping that are utilized in tropical climates
similar to Costa Rica are maize-pumpkin, sweet potato-pumpkin, banana-beans, and sugarcanebeans. All of these examples will work well in humid climates that receive rain throughout the
year. The main purpose of these examples of intercropping is to prevent leaching and soil
erosion by keeping the soil constantly covered (agromisa.org). These combinations also provide
the farmer with more income coming from one field because two component crops are being
39
grown at the same time. The design team felt that intercropping would be a good alternative to
vegetative filter strips in areas that have a high potential of soil erosion that are more than 50
meters away from the stream. The added income will help to further convince the farmer to
implement this BMP, while at the same time the BMP will be helping with soil loss.
Analysis:
BMP Alternative Designs:
The criteria involved in choosing the proper best management practices was based on the
decision matrix (Table 1) which includes total suspended solids reduction, total cost,
maintenance requirements, and area required. The most important aspects of the chosen BMP
system will be those that reduce total suspended solids the most.
Table 1. Decision Matrix.
Variables
TSS
Removal
Total Cost
Maintenance
Area
required
Total
Weight
Extended
Sediment Retention
Detention
Forebay Basin
Basin
Enhanced
Extended
Detention
Basin
Vegetated
Intercropping
Filter Strip
50
4/5
3/5
4/5
4/5
3/5
3/5
25
15
3/5
2/5
2/5
3/5
1/5
2/5
1/5
2/5
4/5
3/5
3/5
2/5
10
4/5
1/5
1/5
1/5
4/5
5/5
100
345
255
265
265
335
310
Where 1 = Low Satisfactory Level
2 = Below Average Satisfactory Level
3 = Satisfactory Level
4 = Above Average Satisfactory Level
5 = Exemplary Satisfactory Level
The decision matrix played a big role in determining which BMPs will be used in the
watershed protection plan. The main criteria the decision matrix was used for was TSS removal,
cost, maintenance, and the area needed for construction. Each of these constraints was then
weighted to determine which one was the most important. To weight each constraint, the team
talked with Mr. Gamez to ensure his needs were met. He expressed that the main goal of the
40
BMP was to reduce TTS, hence the highest weighting for this constraint. Mr. Gamez also
articulated the importance of cost associated with implementation. To determine which BMP
was the best choice for the watersheds, each BMP was ranked in terms of each constraint.
The three basins that were considered, even though they showed good signs of TSS removal
(50 – 90%), were just too costly to construct. The areas that needed the BMPs were not close to
many roads and were in some moderately steep terrain. These site characteristics will make it
hard to build these structures because it will be difficult to get the needed equipment to and from
the site. Also, the amount of equipment needed for construction will increase the cost of
implementation of each of these basins. For this reason, the basins were rated relatively low in
terms of cost. Another downfall of these basins is the amount of land needed for construction.
The basins are going to require great amounts of land that is just not available. Hence the reason
they were also ranked relatively low in this category.
In regards to the vegetated filter strip, it ranked high in almost every category. It has been
found that vegetative filter strips can remove any where between 55 – 95 percent of the sediment
in the runoff from the area. This efficiency is greatly affected by many site characteristics,
including soil type, slope, type of vegetation, etc. Since the vegetative filter strip does not detain
water for an extended period of time, it was not ranked quite as high as the basins in terms of
TSS removal. In terms of cost and maintenance, it ranked higher than all of the other options.
The BMP is more cost effective because not much equipment is needed making the construction
cost much less. Another reason it is much more cost effective is because not a lot of materials
are need to construct the filter strip. Lastly, it was ranked higher in terms of area needed because
it does not require a great amount of area. Usually they are implemented on small patches of
land near streams or adjacent to crop fields.
The last option, intercropping, ranked quite well in most of the categories. Not much
research has been conducted to determine how effective the system is at reducing erosion, but
one study indicated that this type of system can reduce soil loss almost four fold compared to
conventional cropping. The total cost is very similar to the vegetated filter strip, but it is a little
more expensive do to harvesting cost and extra cost involved in planting. This BMP is the best
option in terms of area needed. It ranked the best in this category because it is utilizing empty
space throughout the field. The maintenance was a little more compared to the vegetated filter
41
strip because extra cost and time required for harvesting. By ranking so high in all categories, it
became one of the better options.
By assessing all of the considerations, the vegetative filter strip and the intercropping became
the most applicable BMPs. Even though they did not perform quite as well as the others in terms
of TSS removal, the added benefit of less cost and less area needed, made them more suitable for
the areas in question.
Project Design:
GIS Design Methodology:
To determine the best management practices that best meet the design criteria and fit
within the design constraints an analysis of the current erosion and pollution has to be
determined. The use of the Universal Soil Loss Equation (Equation 1) in conjunction with GIS
analysis was used to determine the areas within the Rio Tibas and Rio Segundo watersheds that
contribute the most to erosion and thus, stream sediment loadings.
A = RKLSCP
(Equation 1)
Where A = average annual soil loss (tonnes/ha);
R = Rainfall and Runoff factor
K = Soil Erodibility factor (tonnes/ha);
LS = Slope steepness and length factor;
C = Cover management factor; and,
P = Conservation practice factor.
The data layers were overlain and each soil type, land use, rainfall amount, slope, vegetation,
and conservation type was converted to appropriate USLE parameters (see Appendix B {There is
no Appendix B or flow chart}for design process flowchart). The elevation layer was acquired
through CATIE from Jeffery Jones while all other layers were obtained from Mr. Gamez during
the site visit. The other layers were a product of a National University graduate student’s work
on GIS in the Heredia Watershed (Nunez).
In order to obtain a slope length factor and slope steepness factor from the elevation layer
Equations 2 and 3 shown below were used in raster calculator in GIS.
L = (Length/22.1)m
(Equation 2)
Where L = USLE L value
Length = Slope length (m)
42
m = m-value
S  - 1.5 
17
1  exp 2.3 - 6.1Sin
(Equation 3)
Where S = USLE S value
θ = Slope percent (Nearing)
Once these equations produced the length factor layer and slope steepness layer Equation 4
below was used to obtain the LS factor layer for the USLE.
LS = (L/22.1)m * (0.065 + 0.04579*S + 0.0065*S2)
(Equation 4)
Where LS = land slope steepness and length factor
L = Slope length (m)
m = m-value
The slope length and M values used are listed in the above equations are listed in Table 2
below.
Table 2. Length factor values for use in Equation 2. (Ward, 2004)
Slope Length Factor
Slope Percent
Slope Length(m)
0 - 1%
30
1 - 3%
61
3 - 5%
91
5 - 8%
122
8 - 12%
152
.=> 12%
183
43
Table 3. M values for use in Equation 2. (Ward, 2004).
Slope Percent
0 - 1%
1 - 3%
3.5 - 4.5%
.=>4.5%
M Value
0.2
0.3
0.4
0.5
The result of the analysis done on the raw data layers in GIS produced LS values attributed to
each cell of the Rio Segundo and Rio Tibas watersheds (Figure 21).
Figure 21. The GIS layer of land slope and steepness factors (LS) in the Rio Segundo
watershed (left) and Rio Tibas watershed (right) based on multiple reclassifications of the
elevation layer.
44
The results showed that LS values ranged from 1.107 to 45.0918 in the Rio Segundo
watershed (left) and 1.109 to 25671.7 {Seems somewhat excessive}in the Rio Tibas watershed
(right). The higher values tended to be towards the upper parts of the watershed which is to be
expected since those areas have slopes from 15 to greater than 60 percent. The northern points
of these watersheds are the peaks of a mountain ridge.
Once the LS layer was out of the way the next step was to reclassify the raw data layers into
the R layer, K layer, C layer, and P layer. The R layer is the rainfall factor layer. This was
produced by converting the polygon feature rainfall layer to raster and assigning each cell the
yearly rainfall amount that the polygon it was in had. Then this layer was reclassified and the
cells were assigned a rainfall factor based on the amount of precipitation each one had per year.
Usually the rainfall factor is obtained from EI30 values, or information regarding storm
duration and intensities. Information regarding these values was not found; perhaps because of a
language barrier in searching and reading journal articles. Instead the rainfall factors were
adapted from a case study for Ethiopia using a yearly average of precipitation (Awoke). This
representation of rainfall values was chosen as a comparison to Costa Rica because of Ethiopia’s
similar tropical environment { I don't think Ethiopia has a similar "tropical" climate. Rainfall in
Costa Rica is much higher.}. Since Costa Rica receives more rainfall than Ethiopia, a regression
equation was developed (Equation 5) and then used to calculate the rainfall (R) factors {Need
more details of what was done and complete reference}.
R = 0.5616*P - 8.2214
(Equation 5)
Where R = Rainfall factor
P = precipitation (mm/month)
The yearly precipitation rates within the Rio Tibas and Rio Segundo watersheds ranged from
200 centimeters at the southern tips of these watersheds to 350 centimeters in the mountainous
northern parts of these watersheds. The resulting rainfall factors are listed in Table 4 below.
Table 4. Rainfall Factors based on total yearly rainfall.
Rainfall Factor
Rainfall (mm)
R factor
2000
1115
2500
1396
3000
1677
3500
1957
45
Using the R factors as listed above, the raster rainfall GIS layer was reclassified to assign
these R factors to each grid cell. The resulting GIS layers are shown in Figure22 below.
Figure 22. The GIS layer of rainfall factors (R) in the Rio Segundo watershed (left) and Rio
Tibas watershed (right) based on reclassification of precipitation values.
This layer correctly depicts the areas of varying rainfall and thus rainfall factors. The next
step was to make a cover factor. A land use feature data layer was part of the set that was given
to us from Mr. Gamez. This layer had already been divided into seven land cover categories.
Cover factors (C) that were derived by averaging values from various case studies (need
references) that used similar land cover categories in similar climates and slopes can be seen in
Table 5 below.
46
Table 5. Cover Factor for land uses present in the Rio Segundo and Rio Tibas watersheds.
Cover Factor
Cover
C Factor
Natural Forest
0.002
Secondary Forest
0.004
Charral
0.007
Pasture
0.010
Pasture and Agriculture
0.030
Permanent Crops
0.380
Urban
1.0
{This –urban, would be for bare soil. Is that you intention?}
These C factor values were assigned to each cell when the feature land use layer was
converted to a raster and then reclassified using the values above. The resulting Cover Factor
layer is shown in Figure 23 below.
47
Figure 23. The GIS layer of land cover factors (C) in the Rio Segundo watershed (left) and
Rio Tibas watershed (right) based on reclassification of different types of vegetation.
The values above were multiplied by 100 in the reassignment process since this tool cannot
use decimal places. The C factor was then divided by 100 when it was inserted into the raster
calculator for the USLE in the last steps of this erosion assessment.
Finally, the Erodibility factor layer was made from the converting the raw soils layer
from feature to raster and reassigning the cells K values (Table 6) based on the amount of silt,
clay, and loam in the soils (Figure 24).
48
Table 6. Erodibility factor for various soils (reference?).
Erodibility Factor
Soil Type
K Value
Inceptisol
0.2
Entisol
0.1
The only significant soil type present in these watersheds is inceptisol soils as can be seen
in Figure 24 below.
Figure 24. The GIS layer of Erodibility factors (K) in the Rio Segundo watershed (left) and
Rio Tibas watershed (right) based on reclassification of soils in the Heredia watershed.
The majority of the watershed is shown to be in Inceptisol soils which are characterized by
little to no B horizon. The particular Inceptisol soil throughout this watershed is the Andept
Inceptisol soil. This is to be expected as this region is known to be surrounded by many
volcanoes and the andept inceptisol is primarily made of volcanic ash (NRCS, 2006).
The last part of the USLE that must be considered is the type of conservation practices being
used throughout the watershed. Unfortunately, no GIS layers were found that show a spatial
49
distribution of this property. An assumption was made to use a Practice Factor (P) of 1. This is
a conservative estimate that assumes that all crops are grown up and down the slope throughout
both the Rio Segundo and Rio Tibas watersheds. The next step was multiplying the cell values
of all of these layers to get the annual amount of soil loss per hectare. Raster calculator is used
to do this using the layers as the inputs into Equation 1 with respect to the factors they represent.
This gives a layer of annual soil loss from each 100 m2 cell of the map. However, we are
looking to see if this land area results in sedimentation to the local streams. To analyze this
spatially in GIS, a multiple buffer ring was used around the rivers and ranked from 10 to 1{I
don't understand what this means. Please explain in detail} in order from closest to the stream to
furthest from the stream. This sediment delivery buffer layer was multiplied by the annual soil
loss layer to produce the final erosion ranking map for the land areas in the Rio Segundo (Figure
25) and Rio Tibas (Figure 26) watersheds.
To determine whether our watershed protection plan would be successful in reducing erosion
throughout the watershed, the C Factor values of pasture and agriculture and for Permanent
Crops were changed to a value of 0.007 to simulate the implementation of our suggested BMPs
(vegetated filter strips). This value was estimated based on a 75% sediment removal efficiency
and relevance to the other land cover values used.
The results of the GIS program that was designed showed that the highest areas of erosion for
the current situation were found to be occurring in the middle regions of the Rio Segundo
watershed closest to the streams as can be seen in the current portion of Figure 25 below.
50
Figure 25. A map of the erosion rankings of land parcels within the Rio Tibas watershed
using the GIS program.
These regions of current high erosion contain mostly permanent crop areas and urban areas
with slopes ranging from 0-15%. Assuming that all of these crop areas implement vegetation
filter strips throughout the permanent crop areas and agricultural areas implement intercropping
then the results indicate that the erosion will have been reduced to low erosion levels in these
areas. The only remaining areas of high erosion after BMP implementation are occurring in the
urban. Similar results occurred in the Rio Tibas watershed.
The GIS program that was designed was used to analyze the current situation of the Rio
Tibas watershed and the results indicated what was expected; that most of the high erosion areas
were occurring in urban areas {This is solely due to your use of C=1 in urban areas. That was a
mistake} and medium erosion was occurring in permanent crop areas in the watershed (Figure
26).
51
Figure 26. A map of the erosion rankings of land parcels within the Rio Tibas watershed
using the GIS program.
The highest areas of erosion were found to be occurring in urban areas near the watershed
outlet. The areas with medium potential erosion were found throughout the middle and lower
regions of the watershed where majority of slopes are 0-15% and the main land use is permanent
crops. When vegetation filter strips are used in all the permanent crop areas of the watershed the
medium erosive areas are almost all reduced to low erosion potentials as can be seen in the
“After BMP Implementation” part of the figure above. The only high erosion areas left are those
in the urban areas which are vegetation filter strips are not designed for.
These results indicate that our suggestion for a watershed protection plan using vegetative
filter strips in all areas of permanent crop land and using intercropping in agricultural areas
would be effective at reducing erosion and sediment transport to streams. This result may be
52
influenced by some of our assumptions. It is conservative to assume that all of the land in these
watersheds are practicing up and down the slope farming or tilling. This would give an
overestimate of soil erosion. The assumption that all permanent crop areas in the watershed
would install and maintain vegetation filter strips and/or practice intercropping is liberal and
would result in a larger change in erosion ranking than in reality. Another assumption that was
made that needs further investigation is that of the efficiency of the vegetation filter strip and
intercropping in sediment trapping and erosion reduction. It was assumed that these practices
would have 75% efficiency as an average of various case studies done in temperate, lower slope
areas than what is occurring in these watersheds. This would result in a C factor that would not
be as accurate as would be liked and a larger reduction in erosion ranking than reality.
Cost Analysis:
In Heredia, money is a big factor in developing a watershed protection plan. Cost is the
limiting factor in determining what the BMPs that will be utilized. For the average resident of
Heredia and the surrounding area, the monthly income is between 500 and 700 United States
Dollars (Luis 2009). Currently all land is given the same value regardless of its erosion potential
(Table 7).
Table 7. Current value for reforestation and maintaining current forest.
Present Value (colones/ha/yr)
Land Classification
Percent of
Reforestation Maintain Forest Watersheds
High
45,000
47,720
6.76
Medium
45,000
47,720
15.44
Low
45,000
47,720
77.79
In order to use the PES program to its fullest, payments should be varied based on each
parcels potential to contribute to suspended solid loads in the waterways (Table 8). For land
areas with a High potential for erosion, the present values should be increased by 50 percent
{how did you arrive at these percents. Need to explain} to encourage more reforestation and
maintaining of forest in the most erosion prone areas. For the Medium erosion potential areas
the value used should remain at the current value. Low potential areas should have their values
53
reduced by 25 percent. This new payment plan will reduce the amount of money paid out for the
protection of lands and could be used for other projects throughout the watershed to protect the
water resources or be used to increase the values paid out to land owners on a case by case basis
if an area is deemed to fall between land classification or above the High potential areas.
Table 8. Suggested values for Reforestation and maintaining current forest.
Suggested Value (colones/ha/yr)
Land
Classification
Reforestation
Maintain
Forest
Percent of
Current Price
High
67,500
71,580
150
Medium
45,000
47,720
100
Low
22,500
23,860
75
These values were obtained from comparing the total value of payments adjusted for
percentage of the area of the watershed they cover.{I don’t understand}
In addition to reforestation and maintaining the current forest, installing a vegetated filter
strip, or implementing intercropping or contour strip cropping { First time contour strip cropping
mentioned - not even defined previously} should reduce the amount of sediment reaching the
rivers (Table 9).
Table 9. Suggested values for other BMPs.
Suggested Value($/ac/yr)
Land
Classification
High
Medium
Low
Vegetated Filter
Vegetated Filter Strip
Strip First Year
Subsequent Years
150.00
37.50
100.00
25.00
80.00
20.00
Intercropping
196.88
131.25
105.00
Contour Strip
Cropping
196.88
131.25
105.00
As the values used for this table were taken from a study in Ohio, we did not feel
comfortable using this as a basis for actual payments. The medium value was determined by
calculating the cost of installing the vegetated filter strip and one year of maintenance for the
54
first column. The cost of labor for a year of maintenance was used for all other years of the
vegetated filter strip. The value for intercropping and contour strip cropping were calculated by
determining the cost to provide seed to implement each year, along with some incentive money.
The medium value was then multiplied by 150% to reach the High values and by 75% to reach
the low value.
Work Plan:
A timeline was created to show when major milestones are to be met throughout the
project. The purpose of the timeline is to ensure that all necessary components are finished with
enough time to write the final report. Two Gantt charts were also created while putting together a
work plan. The first Gantt chart consisted of everything that needed to be accomplished in the
first semester and is shown in Figure 27.
Sep 2008
ID
Oct 2008
Nov 2008
Dec 2008
Task Name
8/24 8/31
1
Form Team
2
Select Project
3
Determine Scope of Work
4
Research BMPs
5
Find GIS Layers
6
Write Literature Review
7
Determine Environmental Concerns
8
Determine Safety and Regulatory Concerns
9
Dr Dillaha in Sudan
10
Fall Final Report Rough Draft
11
Fall Oral Presentation
12
Fall Final Report
9/7
9/14
9/21
9/28
10/5 10/12 10/19 10/26 11/2
11/9 11/16 11/23 11/30 12/7 12/14 12/21
Figure 27. Fall Semester Gantt Chart
The second Gantt chart lists the items that need to be accomplished in the second semester
and when they need to be finished (Figure 28). These charts have helped to visualize the time
frames allotted for each completed task as well as those yet to be finished.
55
Jan 2009
ID
Feb 2009
Mar 2009
Apr 2009
May 2009
Task Name
12/28
1
GIS Map of Critical Land Parcels
2
List of Critical Land Parcels and Owners
3
BMP Options in GIS
4
Economic Analysis
5
Hydrologic Balance
6
Mid-Term Presentation
7
Final Report and Presentation Rough Draft
8
Poster Creation
9
Presentation
10
Individual Oral Exam
11
Final Report
1/4
1/11
1/18
1/25
2/1
2/8
2/15
2/22
3/1
3/8
3/15
3/22
3/29
4/5
4/12
4/19
4/26
5/3
5/10
5/17
Figure 58. Spring Semester Gantt Chart.
First Semester
The first semester mainly consisted of completing background research of our problem. The
team met every Thursday with our advisor to ensure that we were on track with our timeline and
to go over any problems we were having. For the most part, the team worked together on every
aspect of the project. Assignments were divided between team members when the literature
reviews needed to be completed. Due to the amount of research needed for this section, it was
much easier to divide it between members. The main topics that were researched were
alternative BMP, watershed management tools, GIS, and land management in Costa Rica.
Once the semester was completed a second Gantt chart was created to show the actual start
and completion dates of the tasks (Figure 29).
ID
1
2
3
4
5
6
7
8
9
10
11
12
Task Name
Sep 2008
Oct 2008
Nov 2008
Dec 2008
Form Team
Select Project
Determine Scope of Work
Research BMPs
Find GIS Layers
Write Literature Review
Determine Environmental Concerns
Determine Safety and Regulatory Concerns
Dr Dillaha in Sudan
Fall Final Report Rough Draft
Fall Oral Presentation
Fall Final Report
Figure 29. Final Fall Semester Gantt Chart.
56
One of the main accomplishments of the first semester was completing the background
research. By completing this component, each team member gained a better understanding of
the project and alternative BMP’s that could be used in the watersheds. Part of this background
research was compiling GIS layers needed to complete the analysis of the watersheds in
question. Many problems arose when developing these layers. Initially, finding these GIS layers
was supposed to occur in the first part of the semester. By finding these layers, the group was
able to start some of the analysis needed to develop a final solution. Another big
accomplishment was contacting Mr. Luis Gámez. By talking to him, the group was able to gain
an understanding of the project and learn about the current practices the water company was
participating in.
Project Timeline:
(Fall Semester)
Sep. 25
Oct. 8
Oct. 9
Oct. 10
Oct. 22 – 23
Oct. 22
Oct. 30
Nov. 7
Nov. 7 - 22
Nov. 13
Nov. 20
Nov. 20
Dec. 2
Dec. 5
Dec. 10
Dec. 16
Cover page and scope of work
Data Layers accumulated for GIS
Revision of Cover Page and Scope of Work
Project notebook (1)
Dillaha in Oklahoma City
Collect GIS Data
Cover page, scope of work, and resources
Project notebook (2)
Dillaha in Sudan
Cover Page, Scope of Work, Resources, Safety, Regulatory, and
Environmental Considerations and Work Plan
Project notebook (3)
Draft of Final Report (optional)
Oral Presentations and Discussion
Project notebook (4)
Classes End
Revised Final Report.
Second Semester
The spring semester started with a site visit to Heredia, Costa Rica. This visit was
essential to understand the watershed hydrology, culture, and physical environment that will
impact the design constraints and alternatives. A GIS map of critical erosion areas that increase
57
sediment loadings in the watersheds was developed to identify areas contributing the most to
sedimentation.
ID
1
2
3
4
5
6
7
8
9
10
11
12
Task Name
Jan 2009
Feb 2009
Mar 2009
Apr 2009
Find GIS Layers
GIS Map of Critical Land Parcels
List of Critical Land Parcels
BMP Options in GIS
Economic Analysis
Hydrologic Balance
Mid-Term Presentation
Final Report and Presentation Rough Draft
Poster Creation
Presentation
Individual Oral Exam
Final Report
Figure 30. Final Spring Semester Gantt Chart.
Potential BMP options will be analyzed through watershed modeling via GIS. This will
show which BMPs provide the greatest reduction of sedimentation before implementation. A list
of references on urban BMPs will be compiled to meet one of the needs of the client. A
hydrologic analysis will be completed using a GIS. After completing these analyses, the final
design proposal will be compiled and presented to the necessary parties.
Project Timeline:
(Spring Semester)
Jan. 7 - 14
Feb. 2
Feb. 16
Feb. 23
Feb. 26
Feb. 28
Mar. 2
Mar. 3
Mar. 3
Mar. 4
Mar. 5
Mar. 6
Mar. 17
Mar. 19
Site Visit
Project notebook (1)
Mid-Term Project Report
Project notebook (2)
Classification Indices included in Paper
Elaborate on Site Visit
Revised Work Plan
GIS Map of Critical Land Parcels
BMP Options implemented in GIS
Compiled list of Urban BMP Info/Links
Collect Data for Water Balance Equation (SWAT)
Dillaha Away
Economic Analysis
Hydrologic Analysis
58
May 2009
Mar. 19
Mar. 23
Mar. 27
Mar. 30
Apr. 20
Apr. 24
Apr. 27
May 4
May 6
May 7 -12
May 13
Rough Draft of Mid-Term Presentation
Mid-Term Presentation
Dillaha Returns
Project notebook (3)
Draft of Final Report
Poster Creation
Poster Presentation of Final Report
Project notebook (4)
Classes End
Individual Oral Exam
Final Report
Summary and Conclusions {SUMMARY – what is the results and what is needed –
measurement of degree of success?}
The results of this study indicate that the forested areas located in the upper reaches of
each watershed should continue to be protected, as they have proven to be effective at reducing
erosion and soil loss. The current situation of the Rio Segundo watershed show that primary
erosion is occurring in the central region of the watershed closest to the streams where slopes are
between 0-15% and permanent crop land exists. The current situation of the Rio Tibas
watershed show that the primary erosion is occurring throughout the middle and lower parts of
the watershed in areas of primarily 0-15% slope that have permanent crop lands. Both of these
results disregard the high erosion rates that occurred in the urban areas of both watersheds.
Though these areas are not addressed in our GIS analysis, options to reduce sediment through
Urban BMPs have been put into a portfolio that is to be given to Mr. Luis Gamez, our client to
fulfill his questions.
The watershed protection plan that has been concluded on calls for all the permanent crop
lands in both of the watersheds to implement vegetation filter strips around their property and to
incorporate intercropping into their farming practice. This plan will continue to encourage
contracts of reforestation and maintaining forest in all areas of the watershed. The
implementation of these particular BMP’s were chosen in regards to their low costs, low land
area requirements, and high sediment transport reduction.
Reduction of sediment loss on land will reduce sediment in overland flow but produces
higher runoff velocities. The higher runoff velocities will create higher stream bank erosion for
several years until the stream channel recalibrates itself. The result of this higher stream bank
59
erosion will be total suspended solids in the river may maintain or increase in concentration for
the first few years but will come to equilibrium over time. In the long run TSS will decrease.
This is an incentive to maintain the 10 year contracts for all types of Best Management Practices
that the Public Utilities Company of Heredia chooses to support through their Procuencas
Project.
Future work that should be done to further the benefits of this project would include many
things. Field work in determining how efficient vegetation filter strips are in reducing sediment
in tropical areas, the types of vegetation that are most efficient in this process, and a daily or
hourly monitoring system in all of the rivers would help to provide more adequate information
for how successful the land changes would be. It would also be helpful for field work to be done
to determine the USLE factors that represent the vegetation, soils, and climate of Costa Rica
better than that which was used in this project which was obtained from various studies.
Reflections
I (Will Brown) found this project to be both enjoyable and challenging. One of the reasons I
wanted to be a part of this project was to help me determine what I would like to do once I
graduate. Along with developing good teamwork and communication skills, I learned that, given
the chance, I would choose to work on a project that helps conserve and protect natural resources
while improving that area’s standard of living.
I (Matt O’Malley) found there were a few challenging aspects of this project. Since this
project was located in Costa Rica, we had to rely on the knowledge of our contact along with one
site visit. The site visit was not conducted until after the fall semester, and while it greatly
improved our understanding of the project, it would have been more beneficial earlier in the
process. While on the site visit we received the bulk of our GIS layers. The data did not include
any metadata nor did it include the projection used on the layers. Once we were able to obtain
the projection data the GIS portion of the project went relatively smoothly. Finally, on a
personal level, I found it difficult to devote as much time as I would have liked, since I was
taking eighteen credits in addition to the Comprehensive Design class.
I (Whitney Thomas) found this project to be very interesting and to invoke all aspects of the
design process and material learned during the past 5 years here at Tech in the Biological
Systems Engineering program. This project took much more of my time than I had expected and
60
the results are not as satisfactory as I would like because of time and communication limits. It
would have been better to have the project objectives completely narrowed within the first month
of fall semester. This was hard to do since our site visit was during the winter break and since he
had multiple objectives he was looking for us to answer. I enjoyed the site visit to Costa Rica
very much and found that that experience broadened my cultural views as well as engineering
ideas. I also found that working in teams showed me where my strengths and weaknesses lie as
far as being a team member versus team leader.
61
Resources
Advameg Inc., 2008. Costa Rica Agriculture. Encyclopedia of the Nations. Available at
www.nationsencyclopedia.com/economies/Americas.html. (Accessed 25 October 2008.)
ASABE Standard. 2006. Grassed Waterway for Runoff Control. EP464. American Society of
Agricultural and Biological Systems Engineers.
ASAE Standard. 2007. Soil and Water Terminology. S526.3. American Society of Agricultural
and Biological Systems Engineers.
ASAE Standard. 2004. Uniform Terminology for rural Waste Management. S292.5. American
Society of Agricultural and Biological Systems Engineers.
ASAE Standard. 1986. Water and Sediment Control Basins. S442. American Society of
Agricultural and Biological Systems Engineers.
ASAE Standard. 2004. Manure Storages. EP393.3. American Society of Agricultural and
Biological Systems Engineers.
Asquith, N. and S. Wunder (eds). 2008. Payments for Watershed Services: The Bellagio
Conversations. Fundación Natura Bolivia: Santa Cruz de la Sierra.
Awoke, T. C. 2009. Vetiver in the Rehabilitation of the Degraded Zegzeg Watershed in Ethiopia.
Availible at http://www.vetiver.org/TVN_IVC2/CP-1-4.PDF. (Accessed March 3, 2009).
Butler, Rhett A. 2006. “Impact of Deforestation – Soil Erosion.” Mongabay.com / A Place Out of
Time: Tropical Rainforests and the Perils They Face. (Accessed 22 Feb. 2009).
Commonwealth of Puerto Rico. 2003. Puerto Rico Water Quality Standards Regulation.
Resolution No. R-03-5. Available at
http://www.epa.gov/waterscience/standards/wqslibrary/pr/pr_2_wqs.pdf (Accessed date?).
Committee to Review the New York City Watershed Management Strategy, National Research
Council. 2000. Chapter 4: Watershed Management for Source Water Protection. In Watershed
Management for Potable Water Supply: Assessing the New York Strategy. 130 – 157.
Washington D.C.: National Research Council. Available at
http://www.nap.edu/catalog.php?record_id=9677 (Accessed 2 Oct. 2008).
Department of Wildlife, Ministry of Environment and Energy, Costa Rica. 1995. Ley De
Conservacion de la Vida silvestre 7788. http://cecoeco.catie.ac.cr/descargas/CostaRica_
CONSERVACION_ VIDASILVESTRE. pdf?CodSeccion=7&IntMenu=7&MagSigla
=MENU_HERR. (Accessed November 12, 2008).
EPA. 2000. EPA Guidelines Pertaining to Water Sampling (Draft 1).
Gámez, Luis. The Development of Environmental Services Payments in Costa Rica. Public
Utilities Company of Heredia.
Gámez, Luis. Environmental Services Payments and Participation of the Utilities Sector. Public
Utilities Company of Heredia.
Graphic Maps. http://www.worldatlas.com. (Accessed November 20, 2008).
LeGare, Stephanie, Leslie Sierad, and Kevin Waugh. 2005. Preventing Pollution at the Source:
Waste Management on Dairy Farms in Costa Rica. Worcester Polytechnic Institute.
Legislative Assembly of the Republic of Costa Rica. Ley General De Salud 5395.
www.asamblea.go.cr/ley/leyes/5000/5395.doc (Accessed November 13, 2008).
Mayer, Ralph. 2005. Estimated Costs for Livestock Fencing. Iowa State University. Available at
http://www.extension.iastate.edu/Publications/FM1855.pdf. (Accessed December 1, 2008).
Nearing, M.A. 1997. A Single, Continuous Function for Slope Steepness Influence on Soil Loss.
Soil Science Society of America Journal. Vol 61 no 3. NMadison, WI. Available at:
62
http://www.tucson.ars.ag.gov/unit/Publications/PDFfiles/MAN_30.pdf. Accessed Feb 26
2009.
NRCS, 2006. Keys to Soil Taxonomy, Tenth Edition. Natural Resources Conservation Service
and United States Department of Agriculture. Chapter 11, pg. 159. Available at: ftp://ftpfc.sc.egov.usda.gov/NSSC/Soil_Taxonomy/keys/keys.pdf
Pearce, D.W. and C.G. T. Pearce. 2001. The Value of Forest Ecosystems. Montreal, Canada:
The Secretariat Convention on Biological Diversity.
Redondo-Brenes, Alvaro and Kristen Welsh. 2005. Payment for Hydrological Environmental
Services in Costa Rica: The Procuencas Study. MES and MFS.
Southgate, Douglas, and Sevn Wunder. 2007. Paying for Watershed Services in Latin America:
A Review of Current Initiatives. Office of International Research, Education, and
Development (OIRED), Virginia Tech.
Toucan Guides. 2006. Costa Rica Rainy Season Map. Availible at: http://costa-ricaguide.com/Weather/WeatherMap.html Accessed 22 Feb. 2009.
Tyson, T. & S. Mukhtar. 2008. Liquid Manure Storage Treatment Options, Including Lagoons.
Cooperative Extension System. Auburn and Texas A&M Universities. Available at
http://www.extension.org/pages/Liquid_Manure_Storage_Treatment_Options,_Including_L
agoons. (Accessed on December 1, 2008).
University of the Virgin Islands Cooperative Extension Service. 2002. Virgin Islands
Environmental Protection Handbook. Available at
http://www.dloc.com/?b=CA01300680&v=00001. (Accessed 20 Nov. 2008).
U.S. Department of State. 2008. Costa Rica: Country Specific Information.
http://travel.state.gov/travel/cis_pa_tw/cis/cis_1093.html#safety (Accessed November 13,
2008)
Virginia Department of Conservation and Recreation. 1999. Virginia Stormwater Management
Handbook. Available at http://www.dcr.virginia.gov/soil_&_water/stormwat.shtml.
Ward, A.D., S.W. Trimble. 2004. Environmental Hydrology. 2nd ed. United States: Lewis
Publishers. Chapter 11.
World Research Institute. 2006. “Costa Rica: Forestry Law - N 7575.” Available at
http://projects.wri.org/sd-pams-database/costa-rica/forestry-law-n-7575. (Accessed on
November 12, 2008).
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Appendix A
Skills Required
Qualifications:
Land and water resource engineering background
Required prerequisite courses:
CEE 3104: Intro. Environmental Engr.
BSE 3305: Land & Water Res. Engr.
CSES 3114:&3124: Soils & Soils Lab
Required co-requisite courses:
BSE 4304: NPS Pollution Modeling & Management
BSE 4344: Geographic Information Systems for Engineers
Recommended courses/knowledge:
ENGE 2344: Computer Aided Drafting
Spanish
Estimated Commitment from a 3-member student design team:
4-6 hours per week per team member
Skills that must be developed for a successful completion of this project:
Strong writing and team-work capabilities
Basic knowledge of hydrology
Basic knowledge of watershed management planning
Working knowledge of modeling resources
Economic analysis procedures
Advisors:
Dr. Theo Dillaha
Client:
Mr. Luis Gámez of the Public Utilities Company of Heredia, Costa Rica
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Appendix B
GIS Design flowchart
Land Use
Universidad Nacional
Reclassify
Mask: Sub-Basins
Precipitation
DEM-Universidad
Nacional
Feature to Raster
Reclassify
Mask: Sub-Basins
Elevation
DEM-CATIE
Reclassify
Mask:Sub-Basins
Soils
Universidad
Nacional
Feature to Raster
Reclassify
Mask: Sub-basins
Streams
USGS-Universidad
Nacional
Feature to raster
Field: Stream Length
Slope
Spatial Analyst
Slope
100 m Cell size
% Rise
Land Cover
Reclassify
MValue
Reclassify
0-1% = 0.20
1-3.5% = 0.30
3.5-4.5% = 0.40
=> 4.5% = 0.50
Reclassify land use
Into Cvalues
Cover Factor
(C)
Slope Length (L)
Reclassify
0-1% = 30 m
1-3% = 61 m
3-5% = 91 m
5-8% = 122 m
8-12% = 152 m
=> 12% = 183 m
Topographic Factor
(LS)
Raster Calculator
LS = (L/22.1)m*(.065 + .04579*S + .0065*S2)
Reclassify precipitation
Into R values
Reclassify soils
Into K values
Rainfall Factor
(R)
Erosivity Factor
(K)
Sediment Delivery
Buffer
Euclidean distance
Multiple Buffers
10 classes
Sediment Delivery
Potential (SDP)
Reclassify
Values: 1-10
1 =Lowest erosion
10 = Highest erosion
Approximate
Sediment Delivery
Raster calculator
Asd = R * C * LS * K * 1 * (175*2.44)
Ranked
Erosion
Potential
Raster Calculator
RSD = Asd*SDP
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Supplemental Pamphlet
After the site visit to Costa Rica the design team decided that it would be beneficial to
provide Mr. Gamez a supplemental portfolio that included information about urban best
management practices and proper water sampling techniques. This document will be placed on a
compact disk with our final report and sent to Mr. Gamez after the completion of the final report
in order to meet all his needs as our client. The pamphlet provides Mr. Gamez and his associates
an annotated bibliography and pdf files of a few urban BMP handbooks that can be used in the
implementation of some urban BMPs in future work of the Procuencas program. The team felt
that it was crucial for the public utilities company to consider these urban BMPs to further
decrease the erosion and sedimentation within the Heredia watershed beyond the primary focus
of our watershed protection plan. The supplemental document also contains some case studies of
urban BMPs that have been implemented in tropical areas similar to Costa Rica. These case
studies will provide the company with the positive and negative aspects of each BMP. The next
section of the document provides a methodology that describes proper steps in collecting water
samples from the streams. Mr. Gamez stressed that they currently do not have a step-by-step
process that can be used to ensure water samples are being taken accurately and precisely on a
regular basis. Following the water sampling methodology is the process that should be used in
determining how much sediment is in the water sample. This document should provide Mr.
Gamez and the public utilities company with information that can be used to ensure the team’s
design will be comprehensive.
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Urban BMP Case Studies
Source (or Adapted from): International Stormwater BMP Database, 2007. Developed by
Wright Water Engineers, Inc. and Geosyntec Consultants for the Water Environment
Research Foundation (WERF), the American Society of Civil Engineers
(ASCE)/Environmental and Water Resources Institute (EWRI), the American Public
Works Association (APWA), the Federal Highway Administration (FHWA), and U.S.
Environmental Protection Agency (EPA). 1996 http://www.bmpdatabase.org/
The website listed above contains a project that began under a cooperative agreement
between various national agencies, environmental foundations, and professional engineering
societies. The purpose of the project database is to provide quality scientific information to
improve the design, selection, and performance of BMPs. Assessment and review of this data
could ultimately lead to a better understanding of factors influencing BMP performance and
improvements in BMP design, selection, and implementation. The database includes many case
studies that show how well certain BMPs performed under specific conditions. The case studies
are very detailed; including designs, parameters, and constraints. By looking at the performance
of a BMP in an area similar to Heredia, you will be able to determine if that BMP is suited to
your situation. It also provides a basis in terms of economic analysis when implementing a
certain BMP. The database also includes various spreadsheets that can be used when monitoring
an implemented BMP.
The above database also provides a comprehensive list of studies that have been
completed throughout the United States focusing on TSS removal efficiencies of a plethora of
BMPs. The list of BMPs studied include; porous pavement, biofilters, infiltration basins,
wetland basins. The main ones that should be considered for Costa Rica are the biofilters and
porous pavements. The others are large in size and can not be implemented inside the city.
These bigger BMPs, the basins, can be used outside the city in the areas that are currently being
urbanized. Even though these studies do not directly illustrate how these BMPs perform in
climates similar to Costa Rica’s climate, they still give some insight on efficiencies. For
example, the biofilters and porous pavements mainly need soils that are well drained. For the
most part, soils throughout the watersheds and surrounding areas are well drained and allow for
great amounts of runoff infiltration.
Kohler, M., Schmidt, M., Grimme, F., Laar, M., Gusmao, F., 2001. Urban Water Retention
by Greened Roofs in Temperate and Tropical Climate. In Proceedings of the 38th IFLA
World Congress, Singapore.
A team of scientists from Germany have been studying the effects of greened roofs on
urban water quality. The goal of this study was to transfer knowledge of greened roofs of
Central Europe to the tropics (Brazil). The team of scientists from Germany is studying how
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well greened roofs are working in Rio De Janeiro, Brazil. They listed the advantages of the
greened roofs they have found after implementing them in Central Europe. The end of the
document states what they expect the results to be after implementing the greened roofs in
Brazil. They suggest that the alternative roof will cut the peak storm water load from a average
magnitude rain event in the tropics. The average retention rate from the studies done in
Germany was about 50-75% of the total precipitation. The scientists expect the retention rate in
Brazil’s climate to be around 65% of the precipitation. By using the average retention rate and
the amount of annual evapotranspiration, they calculated that approximately 1800 m3 of water
can be retained per hectare of land. By retaining this water, a lot of the problems associated with
pollutant movement with respect to runoff can be minimized.
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Annotated Bibliography – Urban Best Management Practice Handbooks
Department of Environmental Quality. 1999. Urban Best Management Practices for
Nonpoint Source Pollution. Wyoming: Wyoming Department of Environmental
Quality.
The purpose of the above document is to provide a series of conservation practices. The
document includes a compilation of information on several structural and non-structural BMPs
that can be implemented in either urban or suburban areas. The report is intended to be used as a
guideline when trying to determine what BMP will be suited for a given area. Some of the
BMPs included report may require design and construction oversight by a professional engineer
and may also require regulatory permits. The BMPs that will be useful in Heredia include:
vegetated filter strips, porous pavement, concrete grid pavement, and various BMPs for urban
construction.
National Risk Management Research Laboratory. 2004. The Use of Best Management
Practices in Urban Watersheds. Edison, New Jersey: U.S. Environmental
Protection Agency.
The main purpose of this report is to illustrate all of the different BMPs that can be
utilized in a watershed protection plan. The report fully explains why the use of BMPs in urban
areas is critical to the health of the watershed. It also shows all of the BMPs that can be used in
urban situations. The report goes on to explain how to monitor the BMPs once they have been
implemented to help ensure the performance of the BMP is sustained at a reasonable level
throughout the life of the structure. The final section of the report explains some of the cost
associated with the planning and construction of certain BMPs.
South Florida Water Management District. 2002. Best Management Practices for South
Florida Urban Stormwater Management Systems. West Palm Beach, Florida. South
Florida Water Management District.
This document contains information about methods currently being used in South Florida
to improve water quality in the region. The document provides a general overview of
stormwater runoff, the sources that effect water quality, and what can be done to improve urban
stormwater runoff. The last section of the document includes structural and non-structural BMPs
that can be implemented in this region. The document can be very beneficial to the public
utilities company because the climate in southern Florida is similar to the climate in Costa Rica.
69
Water Sampling
To analyze a water sample, care must be taken to ensure the sample is of high quality.
There are certain steps that can be taken to ensure this good quality. During the site visit to
Costa Rica, Mr. Gamez asked the team to provide him with a methodology that can be used in
sampling surface water that will be analyzed for TSS. He asked for a method that was cost
effective and not very time consuming. To obtain representative water samples, the most
accurate method currently is continuous sampling machines. These machines can sample water
in a stream at user specific time intervals. This system allows the user to get representative water
samples throughout the duration of a storm without having to physically be there. These systems
are very efficient but are fairly expensive. After conversing with Dr. Tess Wynn of the
Biological Systems Engineering Department at Virginia Tech, the design team decided the best
sampling device would be a rising stage sampler.
The rising stage sampler (RSS) is a simple, yet accurate device that allows the user to
collect water samples efficiently. The device is basically a pole that has sampling bottles
attached to it. Each bottle has an inverted pipe that serves as the intake, so once the bottle is full
there is no other interaction between the sampled water and the water within the stream. These
can be used in very remote places that do not have to be visited frequently to collect the samples.
Since most of the regions within the watersheds in question, these samplers are appropriate.
Another big upside of these samplers is the low initial cost and low maintenance requirements.
The only downside of the RSS is that don’t give you samples along the entire hydrograph. Since
they don’t sample along the whole hydrograph, they usually overestimate sediment load because
sediment concentration usually peaks before the flow peak (Wynn, 2009).
To obtain more information about water sampling, the team added an additional
document created by Davies Laboratory of Queensland, Australia. The document, Design and
Application of Automated Flood Water Quality Monitoring Systems in the Wet Tropics,
illustrates many water sampling techniques. It contains three different methods for sampling
water and also contains information on sampling locations.
Dr. Tess Wynn. Email conversation. Virginia Tech. Blacksburg, VA. April 29th, 2009.
CSIRO Land and Water Sciences. 2007. Design and Application of automated Flood Water
Quality Monitoring Systems in the Wet Tropics. Townsville, Queensland.
70
How to measure sediment in water
When the design team had a chance to visit Costa Rica over spring break, it was asked of
them to provide a simple, accurate method to help determine the amount of total suspended
solids (TSS) in the water sample. The design team decided that the whole process should be a
supplement to the overall design. The detailed methodology is described below.
The amount of TSS in a stream can provide an insight on how healthy a river or similar
water body is at a certain time. Since TSS is one of the major priorities of the overall design,
there needs to be a way for Mr. Gamez to accurately and quickly measure the amount of TSS in
certain sections of the river. The detailed method described here was found in a handbook called
A Citizen’s Guide to Understanding and Monitoring Lakes and Streams, published by the
Department of Ecology in the state if Washington.
To take an accurate water sample from a study area, one needs to make sure that they do
not disturb the stream bottom. If the stream bottom is disrupted in any way the readings could be
skewed do to the amount of sediment that would be forced into suspension. To take the sample
accurately, one must ensure that they step upstream, lean, and reach into the current for the
sample. After the sample is taken, the rest of the analysis must be completed in a laboratory.
To begin the laboratory analysis, glass fiber filters must be soaked in distilled water then
dried at 103 degrees Celsius. After the filters have completely dried, their weights must be
recorded. Then the dried, weighed filter is placed onto a filtering flask. The water sample needs
to be shaken, then poured into the flask and the pump turned on. The amount of water used may
change according to water conditions. Use 100 mL as a base, but use less water if the filter gets
clogged too quickly and more of the water filters through too fast. Once the amount of water
filtered through is recorded, the filter needs to be dried at 103 – 105 degrees Celsius.
After the filter is dried, let it cool at room temperature and weigh it again. Repeat the
drying, cooling, and weighing of the filter until it reaches a constant weight. Once this process is
done, record the final constant weight. The increase in weight from the initial weighing
represents TSS. TSS is calculated using the following equation:
TSS (mg/L) = ([A-B]*1000)/C
A = End weight of the filter
B = Initial weight of the filter
C = Volume of water filtered
The above process is fairly straightforward and easy to do with a little amount of
equipment. This method is currently the easiest and most cost effective way of determining total
suspended solids.
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WSDE. 1994. A Citizen’s Guide to Understanding and Monitoring Lakes and Streams.
Washington State: Washington State Department of Ecology. Available at:
http://www.ecy.wa.gov/PROGRAMS/WQ/plants/management/joysmanual/4tss.html.
Accessed 21 April 2009.
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