Water Harvesting Monitoring:
Guidance Document For Urban Sites
Sonoran Institute
Authors: Rachel Pergamit and Emily Brott
September 2013
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Table of Contents
Introduction ............................................................................. 3
I. What is Water Harvesting? ..................................................... 4
II. Why Harvest Water? ............................................................. 6
Goal # 1: Reduce Municipal Water Demand ......................................................... 6
Goal # 2: Reduce Flooding and Stormwater Runoff .......................................... 7
Goal # 3: Improve Quality of Life ............................................................................... 7
III. How to Measure Water Harvesting Impact? ......................... 8
A. Examples: Reduce Municipal Water Demand ................................................. 8
B. Examples: Reduce Flooding and Stormwater Runoff ............................... 16
C. Examples: Improve Quality of Life .................................................................... 18
Conclusion .............................................................................. 23
References .............................................................................. 24
Additional Resources .............................................................. 27
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Introduction
For the past 20 years, the Sonoran Institute has been implementing a conservation
and watershed restoration vision for the Santa Cruz River, a 184-mile stretch of unique
wetland habitat that connects Arizona and Mexico. Water harvesting has been a major
component of many watershed restoration efforts. The restoration sites can be found on
county, states, and federal land.
Water harvesting is the practice of collecting or capturing water for beneficial use.
Benefits can range from restoration of wetland habitat to provision of additional water for
home landscape irrigation.
Water harvesting is becoming increasingly common in urban settings. However,
with the diversity of potential benefits, it can be hard to track results or improvements
consistently. Goals for water harvesting also vary from person to person. Sonoran
Institute identified the need for a document to help guide individuals in monitoring the
effects of their water harvesting.
This document will explain types of water harvesting, selected goals of water
harvesting, and multiple examples of tracking those goals. We reviewed literature and
information on water harvesting practices through online research, personal
communications with local experts, and experience from water harvesting courses. This
research helped us identify common water harvesting goals and then explore examples of
how to monitor and report on those goals.
Whether you are thinking about water harvesting, or have already started, this
document will help demonstrate the various benefits water harvesting can have, and how
you can measure its impact.
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I. What is Water Harvesting?
Water harvesting is the practice of collecting or capturing water for beneficial use
instead of allowing it to run off of a site. There are two ways to conduct water harvesting:
active and passive. Active water harvesting refers to constructed systems that usually
require energy to collect, filter, store, and reuse water. A cistern or rain barrel is part of
an active water harvesting system. The "active" component comes from the need to
actively bringing water to plants with a hose, nozzle, bucket, or irrigation system. Passive
water harvesting refers to non-mechanical catchment methods that contain water until the
land naturally absorbs it. A basin is an example of passive water harvesting.
Water harvesting can be further categorized by water source. The most common
source for water harvesting is rainwater. Rainwater harvesting aims to collect, capture,
and use rain before the rain can collect pollutants when it moves across land or
impervious surfaces. Homeowners, property owners, and municipalities can all harvest
rainwater, with adjustments based on the specific sites. An important factor to consider in
rainwater harvesting is the quantity of water available for collection, determined by the
amount of rain that falls on the site itself as well as the amount of rain that flows onto the
site from somewhere else [e.g. neighbor's roof or yard (Waterfall 6)].
A second source for water harvesting is greywater, which is reused water from
myriad sources, including showers and washing machines. Harvesting greywater often
requires professional re-plumbing in order to bring the greywater outside. The type of
source determines the quality and quantity of potential greywater. Showers and laundry
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machines are popular greywater sources because they provide a large quantity of water
and, if certain best practices are followed, tend to have only minor concentrations of
contaminants (Arizona Department of Environmental Quality). A unique benefit of
greywater is the consistent quantity, since it is not dependent on rainfall. Greywater
should not be confused with so-called black water, which includes sewer water, water
that has been allowed to stagnate and become anaerobic, and water that has a high risk of
contamination from bacteria and pathogens (Arizona Department of Environmental
Quality). For example, if treated correctly, kitchen water can be reused as greywater
(Greywater Action). Since it is often not treated properly, most regulations regard kitchen
water as black water.
A third source of water for water harvesting is stormwater, or water that flows off
of a site, such as water in the street. Harvesting stormwater from streets has many
benefits: the water can be used to sustain shade trees and other plants; the water is
diverted and therefore reduces flooding downstream; and, depending on how stormwater
is managed, municipal water treatment costs go down (due to the diversion of water away
from storm drains). One challenge for collecting and utilizing stormwater is that
stormwater picks up pollutants in the streets (oil, grease, pet waste, etc.) and thus should
not be used to grow food plants. Collecting stormwater from streets depends on the
layout and landscape between the street and the planted area. Therefore, stormwater may
not be feasible as a water source for all properties.
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II. Why Harvest Water?
Water is a precious and scarce resource, yet its benefits are frequently squandered
or underutilized. The purpose of water harvesting is to utilize water that falls on
(rainwater), flows on (stormwater), or is produced on (greywater) a given site. Water
harvesting is often supplemented by purchase of municipal water to meet all of the water
needs for the site. Water harvesting takes advantage of a free resource and has many
direct benefits. Some of the most important benefits are: 1) reduced demand on
municipal water supplies; 2) reduced flooding and stormwater runoff; and 3) improved
local quality of life. The effectiveness of your water harvesting efforts can and should be
monitored to ensure maximum benefit. The monitoring strategy employed will differ
based on which of these overarching benefits you are most interested in. Simply put:
what is your goal for the site?
Goal # 1: Reduce Municipal Water Demand
If this is your primary goal for water harvesting, you just want to save water.
Maybe you would like to cut costs on your water bill, or maybe you are concerned about
water scarcity and you want to do your part. Perhaps you are involved in a program like
"Conserve to Enhance" (University of Arizona Water Resources Research Center) and
you want to dedicate your water savings to help restore local rivers. Or maybe your city
has a "water waste" law or water use restrictions and you want to supplement limited
municipal water with other abundant source of harvested water (Albuquerque Water
Authority). Either way, your goal is to do more with less, and so you will measure the
effectiveness of water harvesting "by the gallon." This goal is the most basic and is
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usually the first thing homeowners think of because it is site-specific, personal, and
realizable.
Goal # 2: Reduce Flooding and Stormwater Runoff
This second goal relates to reducing stormwater output, or the amount of water
flowing off of your property. The broader issue of stormwater management is primarily
handled by cities. Managing and treating large volumes of stormwater comes at a high
cost to cities (American Rivers 21). These costs can be reduced by widespread
implementation of rainwater harvesting by citizens. Rainwater harvesting advances this
goal by increasing water infiltrated into soil, thus reducing water flowing into the street.
Reduction of stormwater output can also benefit the wider community by diminishing
hazardous flooding in roadways. Because plants naturally take up and filter pollutants,
widespread stormwater harvesting in vegetated basins is a cheap way to clean water and
irrigated shade trees as the water works its way back into the soil.
Goal # 3: Improve Quality of Life
A third major goal for water harvesting is to bring about myriad but site-specific
improvements to local quality of life.
Local quality of life improvements can take numerous forms, subject to the
interests and needs of the property owner. This publication will address three common
local quality of life goals that are supported by water harvesting: increasing or restoring
native vegetation; improving soil; and improving wildlife habitat. While other quality of
life goals exist (e.g. food production), we have focused on goals associated with
measurable results that could be linked to the effectiveness of water harvesting.
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III. How to Measure Water Harvesting Impact?
To assess the impact of water harvesting, a method of monitoring or measuring
benefits is needed. Proper monitoring can be a powerful tool in reaching informed
decisions about future goals and strategies and in giving objective feedback on current
goals and strategies. For example, if the amount of rainwater collected in a cistern is
substantial, but is not satisfying the water needs of your plants, this could drive a decision
to plant lower water use vegetation. By tracking results of water harvesting, you can also
see the progress and success of current goals and strategies. Monitoring the effectiveness
of water harvesting systems can also alert property owners to maintenance needs. Regular
maintenance is an important practice to ensure continued and consistent benefits and
savings in the long term.
Each of the three common water-harvesting goals described in the previous
section have unique methods for tracking impacts and benefits. Additionally, methods for
monitoring water harvesting effectiveness can range in technical complexity, guidance,
and comprehensiveness.
A. Examples: Reduce Municipal Water Demand
This section will describe various methods to monitor water savings from water
harvesting. After each description, we present additional information on the method's
ease of use, guidance on future water use, and level of comprehensiveness.
1. Monthly Water Bill
The easiest way to track water savings is to monitor a property’s monthly water
bill. Each month, a user would track the amount of water delivered and record the volume.
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While some utility companies show comparisons to previous months, additional personal
tracking would extend this data. Changes in monthly water use could be correlated with
implementation of water harvesting features. Here, the focus would be solely on the
amount of water delivered. Since a water bill is usually an accumulation of charges, water
use is not the sole determinant of the final cost, but can easily be found within the
breakdown of the bill.
Ease of Use: This method is easy to track, as the information is already being
recorded and shared, and is available online. The measurement of delivered water may be
in unfamiliar units (like "ccf" or hundreds of cubic feet) and would need to be converted
to a metric that is understood by the property owner (i.e. gallons).
Guidance on Future Water Use: This method allows an individual to see
variations between months, compare to the average in their city, and accurately track the
amount of water delivered.
Comprehensiveness: The information from a water bill will generally be accurate
in its measurements. But, the comprehensiveness is limited by the simplicity. That is, a
water bill simply measures the total amount of municipal water delivered. It does not
separate between outside and inside use, which section of the house or yard is using the
most water, or give details on how much water is needed (or not needed) in those areas.
2. Cistern Water Level
Net water reduction can also be tracked by measuring the volume of water
collected and held in a cistern. An individual can calculate the amount of rainwater
harvested and consider that amount to be their water savings. In Tucson, cisterns can play
a large role in water conservation in the summer, since desert monsoons can make up to
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half of yearly precipitation (Guido). If you have non-native or other higher water use
plants, the captured cistern water can help supplement their water needs (Strader). One
method to measure the water level in the cistern is to use a pressure gauge. Pressure
gauges use the water pressure in a cistern to measure the depth of water in the tank. To
calculate the water usage from the cistern for a watering session, measure the water level
before and after watering. Best results from monitoring would come from regular tests,
and tests after rain events.
Ease: The technical skills necessary for installation and use will depend on the
model of pressure gauge. If the gauge is electronic, or has remote access, there will likely
be an increased amount of detail for installments. For reading and tracking, the depth of
the water will need to be converted to volume of water using the specific cistern
measurements. Some models can be connected to computers for continual tracking,
though these may be expensive for domestic use. (See "Additional Resources" for
information on purchasing cistern gauges.)
Guidance on Future Water Use: Measuring the water level allows users to assess
how much water is collected by the cistern, and when. This method can provide the
homeowner guidance on how much harvested water could be used for supplemental
irrigation. Comparing precipitation patterns and landscape water budgets to the amount of
cistern water collected and used can provide insight into individual water usage.
Comprehensiveness: This method is fairly comprehensive, as it allows
measurement of captured water in cistern, as well as the option to monitor how much
water a homeowner normally uses during a given watering.
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3. Rainfall calculation
If acquiring and installing a cistern is unreasonable, rainfall calculations provide a
substitute for tracking captured water, whether in a cistern or on areas throughout the
property. This method would require a single calculation and recording after rain events;
repeated tracking could be accomplished easily in a spreadsheet.
These calculations use the measurement of the rainfall and the catchment area to
determine the rainwater captured on a property. This calculation could also be used
specifically for a catchment area feeding a cistern (e.g. a roof). To track the amount of
rainfall, consult local weather statistics, or even better, install a rain gauge on your
property. (See "Additional Resources" for rain gauge information.) Calculating the
catchment area will depend on its shape (Lancaster 126). For a realistic estimate, one
should account for the runoff coefficient of the catchment area surface. This coefficient
represents the amount of rainwater lost to sources such as evaporation, first flush, 1 leaks,
and infiltration. Different surfaces have different porosities, 2 which will affect run-off
rates. Thus, the basic equation for runoff from a rain event would be:
catchment area (ft2) x rainfall (inches) x 1ft ÷12 inches x 7.48/gal/ft3 x runoff coefficient
= net runoff (gal)
(Lancaster 129)
Ease: This method is simple and non-technical. After initial measurements of the
catchment area and determining the appropriate runoff coefficient, the calculation only
1
First flush is an initial amount of roof runoff from a storm, often diverted from entering the cistern as it
can carry debris or pollutants.
2
Porosity refers to how permeable to fluids a substance is, and for rainwater harvesting, affects how much
water will soak into a substance (e.g. a wooden roof) and how much will runoff.
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requires input of the number of inches from each rainfall event. No additional equipment
is necessary for this method unless a rain gauge is purchased.
Guidance on Future Water Use: This method offers the same guidance as others
that track amount of water captured and held. However, since it can be used for an entire
landscape, it can go far beyond what the cistern calculations tell us. It offers an estimate
of accumulated water, which can guide irrigation needs.
Comprehensiveness: Since this is only an input calculation, it does not offer
feedback on water use and serves only as an educated estimate of rainwater harvested.
4. Long Term Comparison Tracking: Conserve To Enhance (C2E)
In Tucson, Arizona, a local water conservation program called Conserve to
Enhance (C2E) monitors participant water use, compares current use to past usage rates,
and converts volume of water conserved to the monetary value of the water. The program
tracks participants’ current use through Tucson Water, the local utility. Each quarter,
participants receive a statement comparing their current use to their “historical use,” an
average of their water use from the previous three years. Monthly water savings are
converted into dollar amounts and totaled. The goal of the program is to help participants
track water savings and encourage them to donate the monetary value of the water to
local wash restoration projects.
While the program aims to link water conservation to local environmental
enhancement, individuals can adopt this method of monitoring to more thoroughly assess
net water reductions. This method would require securing historical usage of water for
the property beyond what is normally stated on a water bill. Historical use can be secured
for a household from the water utility with proper account information. Then, monthly
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water use could be tracked, compared to the historical average and converted according
to local water rates to the monetary value of the water reduction. With a spreadsheet,
these calculations could be easily repeated each month.
The program is currently expanding within Tucson and to other cities. For more
information, contact University of Arizona's Water Resource Research Center or visit
www.conserve2enhance.org.
Ease: Long-term comparison tracking requires initial efforts but the continued
monitoring is simple and non-technical. It is slightly more intensive because of the need
to acquire the historical information and water rates, but this is only a preliminary time
investment. If you join C2E, then the program will track water savings and water use on
your behalf. As a participant of the program, these are calculated and presented monthly
by C2E, which makes it easy to track and monitor water use and water savings.
Guidance on Future Use: This method incorporates long-term savings and
monthly changes, which can accommodate seasonal and yearly fluctuations. The
comparison to historical water use can shed light on the successes and challenges of
water savings efforts, past or present.
Comprehensiveness: This method collects multiple layers of data, giving a more
complete view of water savings and water use. Since this method tracks water use in
large units (ccfs, equal to 748 gallons), smaller but measurable savings may not register.
5. Tucson Rainwater Harvesting Ordinance Requirements
In 2008, Tucson adopted the first municipal rainwater harvesting ordinance for
new commercial developments. The ordinance requires that 50% of the estimated yearly
landscape water budget be provided by "rainwater harvested on-site by a rainwater
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harvesting system" (City of Tucson Mayor and Council). As part of this ordinance, a
method to assess and track landscape irrigation needs and water use was developed.
The method required for commercial developers to follow includes a landscape
water budget and metering. While designed for commercial properties, this method can
be scaled down for small private sites. A landscape water budget will incorporate
calculations for area of irrigated landscape, the type of plants and their level of water use,
and monthly evapotranspiration rates. Area of irrigated landscape will require
measurements and simple calculations of area. Water requirement calculations,
delineation of low, medium, and high water use plants, and evapotranspiration rates can
be found in sources such as Rainwater Harvesting for Drylands, by Brad Lancaster, and
in online searches for a specific region, or university extension networks (Lancaster 136).
The best method for metering is a sub-meter that only tracks water used for landscaping,
and can give more accurate assessment of outdoor water use (See "Additional Resources"
for sub-meter information). Estimates of outdoor water use range from 40-60% of total
potable water delivered, which is too broad of a range to precisely track use. Calculating
rainwater harvested and used can be achieved by calculating diverted rainwater and any
rainwater held in cisterns.
The calculation used in the ordinance is: LID = PCA x ETo x PC x 7.48
LID - Landscape Irrigation Demand
PCA - Plant Canopy Area in feet
ETo - Reference evapotranspiration rate (loss of water from the soil)
PC
- Plant coefficient (pertains to amount of water used by specific plant)
7.48 - The number of gallons in a cubic foot of water
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Thus, this method can track net water savings in three ways. If conducted before
implementing water harvesting features, it can provide a baseline that, when compared to
later results, would demonstrate the changes to landscape irrigation demands and
rainwater harvested. The irrigation sub-meter would be instrumental to continual tracking
of water savings, while the other calculations would only need to be changed if landscape
features were altered.
Ease: This method is very technical, especially when calculating the precise
amount of rainwater harvested, conveyed, captured, or distributed among different
features. Calculating the landscape irrigation demand requires location-specific research,
measurements of landscape area and analysis of plant water use levels. An irrigation submeter will need to be purchased and installed.
Guidance on Future Water Use: This method offers substantial guidance for
future water use. These calculations can show opportunities for further water reductions
by changing landscape vegetation and augmenting rainwater harvesting features. It also
accurately portrays the amount of potable water used outdoors for a specific location.
Comprehensiveness: The ordinance requires an extreme amount of detail,
accomplished by careful measuring and calculation for each focus area. Thus, each
component (demand, harvested rainwater, or irrigated water use) that can be followed
will supply information on water use. With continual tracking, this will lead to detailed
information on actual water reduction.
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B. Examples: Reduce Flooding and Stormwater Runoff
Runoff from storms and other water outputs often accumulates within a property
and overflows into streets during large storm events. Once in streets, stormwater can
create flooding hazards. Water harvesting can diminish an individual's contribution to
urban runoff and decrease the number or volume of standing pools within a property.
This section will address methods to measure stormwater runoff and assess damages (or
damages avoided).
1. Measuring change in runoff
The first step to tracking change in runoff is to measure the baseline amount of
runoff from a property. To do so, measure the total catchment areas of a property: roof,
driveway, other paved surfaces, and even bare soil. Calculate maximum potential runoff
using the area, rainfall, and runoff coefficients (Lancaster 48, Computer Support Group).
If there is also "run-on" (stormwater that flows onto the property from outside areas) that
should be measured or estimated as well. After implementing water-harvesting features,
measure the catchment areas and calculate the volume of rainwater held on the property.
This can be an estimate of stormwater runoff prevented.
2. Monitoring degradation
A second method to assess stormwater reduction is to monitor areas on the
property where stormwater has created hazards or problems after rain events (Lancaster
31). Walking the property after a rain will show where the water pools, how it flows,
whether erosion is occurring, and whether erosion from runoff is creating gullies 3.
3
A gully is defined as a trench which was originally worn in the earth by running water and through which
water often runs after rains. If left untreated, gullies generally get worse over time.
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Record problem spots and make notes about the estimated volume of pools (area x depth),
or severity of the erosion. This should inform water harvesting plans so that this water
can be directed toward a beneficial use such as vegetation. After implementing water
harvesting/stormwater reduction features, walk the property again after rain events. Note
any changes such as number or volume of pools, level of erosion, or if water flows off the
property.
3. Calculate holding capacity of features
If water harvesting features are in place, calculating the total catchment area that
produces runoff may overestimate the volume of stormwater runoff contributed. To
accommodate for this, one could calculate the holding capacity of the water harvesting
features by using the geometry of the basin and calculating the volume (See Additional
Resources for sample calculation). Then, subtract the volume held by water-harvesting
features from the volume produced from the total catchment area. This would result in a
more accurate calculation of volume of stormwater contributed.
If an individual has not implemented water harvesting features yet and is looking
to reduce stormwater, features can be designed to hold runoff from a range of levels of
storm intensity. Generally, you may want to consider a range from the annual average
storm to a 50-year storm. Then, these features can be measured after storms to estimate
stormwater runoff prevented. If the features overflow, that means the basin's capacity was
exceeded.
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C. Examples: Improve Quality of Life
This section will focus on selected quality of life improvements that can be
noticeably aided by water harvesting. Since these are indirect benefits of water harvesting,
other factors affect success toward these goals. It may be hard to determine the extent of
the impact that arises directly from water harvesting. However, these selected
improvements depend strongly on supplemental water, which would presumably be
gained from water harvesting. Either way, it is important to monitor these effects and
gather data and notes for reference and guidance.
Keeping a regular monitoring journal and taking photographs is a tracking method
that can be applied to all quality of life goals. Panoramic pictures and regular pictures
from set points on a property will give a more complete record of progress and change.
Photo points can be used to document change of a specific feature of your landscape.
Before setting up your photo points, consider spots and a scale where changes will be
noticeable, there is available light, and the photo will include some of the surrounding
area. The surrounding area is area likely to be affected by feature changes and will give
context. It is also good to consider what time of year will best show any effects. After
taking initial photos, record the location and direction of the camera, such as on a map
with notes. For progress pictures, try to take them at the same season or month as the
original photos (United States "Photo Point Monitoring"). If possible, it is recommended
to take photos during different seasons. "Opportunistic" photos, which are less formal and
not intended to be repeated, can also be useful (e.g. after a monsoon) (Oregon Watershed
Enhancement Board).
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1. Improve or restore native habitat
Water harvesting can provide increased available water for vegetation, which can
be used for native or non-native plants. Here are a few different methods to measure
vegetation changes (United States "Measuring and Monitoring"159-208).

Counting the number of plants on the landscape. Can more vegetation be
planted than before? Tracking the quantity of plants that can be sustained can
demonstrate the added benefit of water harvesting.

Tracking the life span of plants. Are plants living longer? Water harvesting
can enable plants to develop larger root zones, making them more droughtresistant, which could then increase the life span. Life span may be negatively
affected by unusual weather.

Monitoring success of plant selections. Are large plants or trees now a viable
option? Are high water use plants getting enough water now? Track
vegetation planted and note the types of plants and their water use level. This
can be combined with the two previous methods to assess the progress of
small native plants, native trees, and non-native species.

Measuring width and height of plants or the diameter of a canopy. Are plants
growing more or quickly? Are they healthier? Rainwater can carry more
nutrients and fewer harmful chemicals than municipal water, which can aid
plant growth.
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2. Improve soil moisture
Through the rainwater harvesting features, the increased amount of time water
remains on soil will increase infiltration, which can help improve soil moisture. Water
harvesting can be instrumental to improving soil moisture, helping to retain water for the
soil that would otherwise flow off. Adequate soil moisture is essential for plant growth
and survival.
Note: Desert soils (aridisols) are mostly sand and clay, not loam (like regions with
higher rainfall). This can negatively affect the soil's ability to hold water. They are also
alkaline (basic, not acidic) and have little organic matter. Native plants are adapted to
existing soils, though the soil can still benefit from added nutrients. This means that
mulching is essential to a well-designed water harvesting system. Organic mulches, such
as wood chips or leaf litter, are best at regulating soil temperature and can help add
nutrients to the soil, though inorganic mulches, such as rock, can still be useful for
collecting water and reducing runoff within features (City of Phoenix).

Visible observations: Record visible observations of the soil regularly, and if
possible, before water harvesting is implemented. Is the soil cracked or dry? Is
it spongy? (Lancaster 30-32)

Hand-feel or squeeze test: Remove small samples of soil at the surface and
from a depth of 2-3 inches. Feel and squeeze the soil to test for moisture. Very
dry soil will be powdery and chunky. Wet soil will remain in a ball or stick to
a shovel or spade. If the soil crumbles freely, it is at good moisture levels for
gardening or other forms of working the soil. Compare to a soil moisture
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interpretation chart to estimate soil moisture deficiency and available water
(Montana Natural Resources Conservation Service). Record the results of this
test. This can be performed after rain events for further detail.

Use a soil sampling tube: A soil sampling tube has a sharpened bottom and
wide slot along the side so when withdrawn, the tube is filled with soil. The
core can be viewed and then removed for further testing. This can be used to
get deeper in the soil, examine soil at different levels, and send the sample to a
laboratory for tests (Plank). County extension websites can offer lists of
laboratories that perform soil testing (Arizona Cooperative Extension).

Use a tensiometer or other soil probes: A tensiometer uses the surface tension
of water to measure the soil moisture. It is a rigid, sealed tube filled with
water, with a vacuum gauge at the top and a porous tip to allow sensing of
amount of available water. They can be portable or permanent. If installed and
used properly, tensiometers will give a very accurate assessment of soil
moisture. This can guide where additional watering is needed, as well as
changes in baseline soil moisture. However, the soil may need to be probed in
multiple locations on a property for detailed results or if there are marked
differences in soil and plant characteristics (Plank).
o To use and track: Probe the soil at the appropriate depth and
placement for tensiometer, depending on the depth of the root zone
and size of the tensiometer. Tensiometer gauge readings can be
interpreted using a chart supplied with the equipment, found online,
or through an extension network.
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3. Improve wildlife habitat
Water harvesting can help to provide and sustain features of habitats. While one
home may not provide enough features to establish an entire habitat, it can aid the larger
habitat area. This makes improving wildlife habitat a prime example of a quality of life
goal. In some cases, such as at a home near a park, or in a neighborhood with multiple
habitat features, various aspects could work in tandem to create good wildlife habitat.

Comparing to National Wildlife Federation (NWF) Checklist: The NWF has a
program for places in commercial and residential areas to become Certified
Wildlife Habitats®. For certification, a yard must have a water source, cover,
food source, and a place for wildlife to raise young. Steps to create a wildlife
habitat and certification can be found online at NWF.org (National Wildlife
Federation). This can also be used as a reference or goal for features that
water harvesting can help support. Record what the yard already provides and
where additional features can be implemented. For example, your landscape
may already have plenty of cover to help protect wildlife, but does not yet
provide enough food sources.

Monitoring journal: Keeping a journal of observed wildlife, including date and
time, will give insight into the responses of wildlife to landscape features. This
can be very helpful to monitor changes after adding water harvesting features, or
vegetation aided by water harvesting. The USA National Phenology Network,
which works to track the impact of climate change on plants and animal life
stages has forms to guide monitoring at usanpn.org.
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Conclusion
The need for an integrated approach to tracking water harvesting effectiveness came to
light through conversations with Tucson Conserve to Enhance (C2E) participants. Many
C2E participants actually saw their water use increase after installing water harvesting
features, due to the two to three year period in which native plants need additional water
to establish their root system. Thus, we tailored this document to help people think about
and track the additional benefits of water harvesting (beyond water savings) to provide a
more holistic picture of conservation impact. We hope this document has provided you
with ideas about the myriad benefits of water harvesting, and how you might design and
monitor your system to meet your personal goals.
Special Acknowledgement:
The authors owe a debt of gratitude to the Tucson-based nonprofit Watershed
Management Group, and Brad Lancaster, who provided much of the inspiration and
technical resources for this work. Learn more about Watershed Management Group's
water harvesting coursework and volunteer opportunities at www.watershedmg.org . Find
Mr. Lancaster's books at http://www.harvestingrainwater.com/books/orders/.
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References
Albuquerque Water Authority. "Water by the Numbers." Welcome to the Albuquerque Water
Utility Authority. Albuquerque Water Utility Authority, n.d. Web. 9 July 2013.
<http://www.abcwua.org/Water_by_the_Numbers.aspx>.
American Rivers, and Center for Neighborhood Technology. "The Value of Green
Infrastructure- Full Report." Resources and Publications. American Rivers and Center
for Neighborhood Technology, n.d. Web. 22 Apr. 2013.
<www.americanrivers.org/assets/pdfs/reports-and-publications/the-value-of-greeninfrastructure.pdf>.
Arizona Cooperative Extension. Laboratories Conducting Soil, Plant, Feed or Water Testing.
Tucson: Arizona Cooperative Extension, 2010. College of Agriculture and Life Sciences.
University of Arizona, May 2010. Web. 21 June 2013.
<http://cals.arizona.edu/pubs/garden/az1111.pdf>.
*Note: The one Tucson lab listed specializes in water testing. Columbia
Analytical Services is a lab not on this list that performs soil testing. They are a national
company with many locations, including Tucson. http://www.caslab.com/TucsonLaboratory.
Arizona Department of Environmental Quality. Using Gray Water at Home. Phoenix: Arizona
Department of Environmental Quality, 2011. Web. 21 Feb. 2013.
<http://www.azdeq.gov/environ/water/permits/download/graybro.pdf>.
City of Phoenix. "Mulch and Soil." City of Phoenix. City of Phoenix, n.d. Web. 17 June 2013.
<http://phoenix.gov/waterservices/wrc/home/outdoor/mulch.html>.
City of Tucson Mayor and Council. Tucson (Arizona). City of Tucson Mayor and
Council. Commercial Rainwater Harvesting Ordinance. Tucson, Ariz.: N.p., 2008. Print.
24
Computer Support Group. "Rainwater Collection Calculator."CSGNetwork.com. N.p., n.d. Web.
9 July 2013. <http://www.csgnetwork.com/rwcollectioncalc.html>.
Evans, Robert, D. K. Cassel, and R. E. Sneed. "Measuring Soil Water for Irrigation Scheduling
Monitoring Methods and Devices." Bio and Ag Engineering Extension. North Carolina
Cooperative Extension Service, June 1996. Web. 09 July 2013.
<http://www.bae.ncsu.edu/programs/extension/evans/ag452-2.html>.
Greywater Action. "About Greywater Reuse." Greywater Action, n.d. Web. 09 July 2013.
<http://greywateraction.org/content/about-greywater-reuse>.
Guido, Zack. "Understanding the Southwestern Monsoon." Southwest Climate Change Network.
University of Arizona, 22 July 2008. Web. 17 June 2013.
<http://www.southwestclimatechange.org/feature-articles/southwest-monsoon>.
Lancaster, Brad, and Joe Marshall. Rainwater harvesting for drylands and beyond. Tucson,
Ariz.: Rainsource Press, 2008. Print.
Montana Natural Resource Conservation Service. "Estimating Soil Moisture by Feel and
Appearance." Montana NRCS. United States Department of Agriculture, n.d. Web. 25
July 2013. <http://www.mt.nrcs.usda.gov/technical/ecs/agronomy/soilmoisture/>.
National Wildlife Foundation. "Create a Certified Wildlife Habitat." NWF.com. National
Wildlife Foundation, n.d. Web. Feb. 2013. <http://www.nwf.org/How-to-Help/Gardenfor-Wildlife/Create-a-Habitat.aspx>.
Oregon Watershed Enhancement Board. OWEB Guide to Photo Point Monitoring. Salem, OR:
Oregon Watershed Enhancement Board, 2007. Oregon Watershed Enhancement Board.
State of Oregon. Web. June 2013.
<http://www.oregon.gov/OWEB/docs/pubs/photopoint_monitoring_doc_july2007.pdf>.
25
Plank, C. Owen. Soil Testing for Home Lawns & Gardens. N.p.: University of Georgia College
of Agriculture and Environmental Sciences, Mar. 2000. PDF.
Sarah, Tony. Summer Watering Techniques for Southern Arizona. Tucson: The Magic Garden
Nursery, n.d. PDF.
Strader, Linda. "Watering Landscape Plants during Monsoon Season (Photos)."Examiner.com.
Clarity Digital Group LLC, 22 July 2012. Web. 17 June 2013.
<http://www.examiner.com/article/watering-landscape-plants-during-monsoon-season>.
United States. Department of the Interior. Bureau of Land Management. Measuring and
Monitoring Plant Populations. By Caryl L. Elzinga, Daniel W. Salzer, and John W.
Willoughby. Denver: GPO, 1998. Print. 1730-1.
United States. Forest Service. Remote Sensing Applications Center. Photo Point Monitoring. By
Randy M. Hamilton. N.p.: n.p., n.d. US Forest Service. Web. June 2013.
<http://www.fs.fed.us/eng/rsac/invasivespecies/documents/Photopoint_monitoring.pdf>.
University of Arizona Water Resources Research Center. "Conserve to
Enhance." wrrc.arizona.edu. N.p., n.d. Web. 9 July 2013.
<http://wrrc.arizona.edu/conserve2enhance.html>.
USA-National Phenology Network. USA-NPN Plant and Animal Phenophase Definition.
Publication. N.p.: n.p., 2012. Usanpn.com. USA-National Phenology Network. Web.
May 2012. <https://www.usanpn.org/files/shared/files/USA-NPN_Phenophase_defsreport_FINAL.pdf>.
Waterfall, Patricia H. Harvesting rainwater for landscape use. 2nd ed. Tucson, AZ: Arizona
Dept. of Water Resources, Tucson Active Management Area, 1999. Print.
26
Additional Resources
At Home Soil Tests. http://organicgardening.about.com/od/soil/a/easysoiltests.htm
After the Storm: A Citizen's Guide to Understanding Stormwater, EPA.
http://water.epa.gov/action/weatherchannel/upload/2008_09_12_weatherchannel_after_th
e_storm-read2.pdf
Cistern Gauges. http://www.harvesth2o.com/PR_CisternGauge.shtml and
http://www.cisterngauges.com/technical.html
City of Tucson Development Standard No. 10-03.0 Commercial Rainwater
Harvesting. http://cms3.tucsonaz.gov/files/dsd/DS_1003_Commercial_Water_Harvesting_04-27-09.pdf
How Much Rainwater Can I Collect, The Gulf Islands (B.C.) Rainwater Connection.
http://www.rainwaterconnection.com/rainwater_harvesting/how_much.htm
Rainwater Collection: Passive Water Harvesting, University of Arizona Cochise
County Cooperative Extension Water Wise Program.
https://wrrc.arizona.edu/sites/wrrc.arizona.edu/files/UA%20Cochise%20Cty%20Extensio
n_Rainwater%20Collection-%20Passive%20Water%20Harvesting.pdf
Rain Gauges: Rain gauges can be purchased at hardware stores, garden stores, and
online. For more information on choosing, reading and installing rain gauges, visit:
http://rainlog.org/usprn/html/main/choosing-a-gauge.jsp
Rainwater Harvesting Guide for Albuquerque (includes runoff coefficients).
http://losalamosextension.nmsu.edu/documents/rainwater_harvesting.pdf
Tensiometers for Soil Moisture Measurement and Irrigation Scheduling, Allen G.
Smajstria and Dalton S. Harrison. http://edis.ifas.ufl.edu/ae146
Tucson Water Harvesting Guidance Manual, Ann Audrey Phillips.
http://cms3.tucsonaz.gov/files/transportation/2006WaterHarvesting.pdf
Southern Arizona Native Plant List.
http://www.harvestingrainwater.com/tucson-az-plant-lists/southern-arizona-native-plantlist-for-rain-gardens/
Sub-meters and Metering Water.
http://www.azwater.gov/AzDWR/StatewidePlanning/Conservation2/Documents/docume
nts/MeteringWater-FINAL31709.pdf
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Sample Calculations
Example of conversion of depth of cistern to volume of water
The basic equation to determine volume of water held in a cistern is:
π × (cylinder radius (ft))2 × depth of cistern water (ft) × 7.48 gal/ft3 = volume of water held
Example: A cistern is 3 feet in diameter and 9 feet in height. A pressure gauge
measures the depth of water to be at 4 feet. The radius is half of the diameter, so the
cylinder radius is 1.5 feet. Thus, the calculation would be as follows:
π × (1.5 ft)2 × 4 ft × 7.48 gal/ft3 = 211.49 gallons
Example of holding capacity of a basin
The volume of a basin will be its holding capacity of rainwater, which is
calculated using the length, width, and depth of the basin. For a rectangular basin (or a
basin roughly this shape) that is 3 feet long, 2 feet wide, and 1 foot deep, the calculation
of holding capacity would be as follows:
3 ft x 2 ft x 1 ft = 6 ft3 (cubic feet) of water
Example of Landscape Irrigation Demand
The landscape irrigation demand is calculated using the area covered by plants
(PCA), evapotranspiration rate (ETo), and plant coefficient (PC). 7.48 is the number of
gallons of water in a cubic foot of water. The example calculation will be for a 10 by 2
foot space in January covered by grass, a high water use plant. For further descriptions of
terms and additional sample calculations, see the link for the development standard in
Additional Resources.
City of Tucson Commercial Rainwater Harvesting Development Standard
LID = PCA x ETo x PC x 7.48
LID = 20 ft2 x 3.0 inches x 1 ft/12 inches x 0.65 x 7.48 gallons/ft3
= 24.31 gallons of water for January
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