An Analysis of Household Rainwater Harvesting Systems in Falelima, Samoa By Timothy M Martin A Report Submitted in partial fulfillment of the requirements for the degree of Master of Science in Civil Engineering Michigan Technological University 2009 Copyright © Timothy M Martin 2009 This report “An Analysis of Household Rainwater Harvesting Schemes in Falelima, Samoa” is hereby approved in partial fulfillment of the requirements for the Degree of Master of Science in Civil Engineering. Civil and Environmental Engineering Master’s International Program Signatures: Report Advisor _________________________ David Watkins Department Chair _______________________ William M Bulleit Date ______________________ ii
Preface This study is based on the 27 months I served with as a U.S. Peace Corps Volunteer from June 2006 through August 2008 in the Pacific nation of Samoa. I served in the village based development program assisting the village of Falelima, Samoa on the island of Savai’i. This report is submitted to complete my master’s degree in Civil Engineering from the Master’s International Program in Civil and Environmental Engineering at Michigan Technological University. It focuses on work completed to expand rainwater harvesting capabilities of Falelima. iii
Table of Contents Preface Table of Contents List of Figures List of Tables Acknowledgements Abstract 1.0 Introduction 2.0 Background Information for Samoa and Falelima 2.1 Geography and Environment 2.2 National History 2.3 People and Culture 2.4 Water and Sanitation 2.5 Falelima, Savai’I 2.6 GEF UNDP Grant Project 3.0 Methods and Data 3.1 Precipitation 3.2 Collection Area 3.3 Water Storage 3.4 Water Demand 3.5 Rainwater Harvesting Model 4.0 Results and Discussion 4.1 Design Curve 4.2 Meeting Basic Access Requirements 4.3 Using Variable Demand Levels 5.0 Conclusions and Recommendations References Appendix A:Village Data B: Rainfall Data iii iv v v vi vii 1 4 4 5 7 8 9 12 18 18 21 22 23 25 31 31 34 38 38 41 42 45 iv
List of Figures Figure 1: Map of Oceania Figure 2: Map of Samoa Figure 3: Tank reinforcement on formwork Figure 4: Appling second ferrocement layer Figure 5: Completed tank Figure 6: Modeled daily water storage at Family 40 household Figure 7: Modeled daily water storage at Family 40 household with rationing Figure 8: 50 l/c/d curves for years 2006 – 2008 Figure 9: Design Curves for Falelima Samoa (100% reliability) Figure 10: Demand curves for various reliability rates. Figure 11: Families initial per capita ability for water supply Figure 12: Families water supply capacity at the completion of tank construction 5 10 16 16 17 30 31 32 33 34 35 36 List of Tables Table 1: Tank Materials and Costs Table 2: Recorded Annual Rainfall in Falelima, Samoa Table 3: WHO Water Service level definitions Table 4: Model Parameters Table 5: Model Results Table 6: Model Parameters for Household 40 Table 7: Initial model calculations for Family 40 household Table 8: Families in each range of daily water supply before and after the water project Table 9: Families in each range of daily water supply before and after the water project Table 10: Families not exceeding basic water access of 20 l/c/d Table 11: List of possible solutions for families to exceed 20 l/c/d and their estimated costs. 14 20 24 26 28 28 29 29 36 37 38 v
Acknowledgments I would like to thank the village of Falelima, Samoa for welcoming me into their community for the two years I spent with them as a Peace Corps Volunteer. In particular my host family of Tauoa Ropiti from whom I learned so much about Samoan culture and hospitality. I must also thank my fellow PCVs for their friendship and support through struggles and joys of living in a new and interesting culture. At Michigan Tech I would like to thank my advisor Dr. David Watkins and committee members Dr. Brian Barkdoll and Dr. Michele Miller. Also the faculty, staff and students of the Department of Civil and Environmental Engineering who I feel privileged to have known and worked with throughout my undergraduate and graduate studies. I must also thank all the members of the Peace Corps Master’s International community who became such good friends. Finally I must thank my family for their continued love and support. They have always encouraged me to take advantage of every opportunity whereever it took me around the globe. vi
Abstract Since the acceptance of and commitment to the Millennium Development Goals (MDGs) there have been major gains in reducing the percentage of the global population without access to improved sources of safe water to meet individual basic needs. However in many regions, as more people gain access, the average difficulty of providing access to the remaining population without access increases as the simple or easier solutions are completed and areas of greater water stress remain. In the Pacific island nation of Samoa access stands at approximately 90%. The remaining 10% of the population resides in areas of limited surface or ground water resources. Many of these communities have turned to rainwater harvesting as a supply source. The village of Falelima, Samoa on the island of Savai’i is one such example. Residents meet their fresh water needs through rainwater harvesting but the ability to collect and store rainfall varies greatly between individual families. This report has two goals. First it examines the systems requirements for rainfall collection and storage needed to provide a family with various service levels of water throughout the year by using a model based on the daily annual rainfall data available. The model is used to produce reliability design curves for the village that can allow users or outside agencies to determine how the addition of system capacity will increase the water available to a family. Second, the effects of a grant by the Global Environmental Facility (GEF) for the construction of ferrocement rainwater storage tanks are examined and recommendations are made for further work to ensure all families with a minimum level of service. vii
1.0 Introduction Access to improved drinking water supplies has increased globally and is on track to meet or exceed the Millennium Development Goals, MDGs, in most regions of the globe. However, the Sub‐Saharan Africa and Oceania regions are not currently on track, and coverage in Oceania has actually decreased by 1% from 1990 to 2006(UNICEF 2008). In order to ensure that these targets are reached, efforts must be stepped up to provide solutions that meet the needs of rural and isolated populations. To do this, modern technology and traditional methods must both be considered to provide water that is safe and in quantities to meet basic needs. As areas of water stress and water scarcity have increased globally, there has been increased interest in alternatives to the use surface of ground waters that are the source of most modern water supply systems. One such alterative, rainwater harvesting, is an ancient technology with evidence of systems in India dated as early as the third millennium BC. Throughout history, civilizations around the globe have used rainwater to supply their water demands(Gould and Nissen‐Petersen 1999). The use of rainwater harvesting systems continues today and is growing in both the developing and developed world. Projects in Thailand and Kenya have greatly increased access to potable water, and rural areas of New Zealand and Australia have a long history of using rainwater harvesting where low population densities render municipal supplies economically unfeasible(Gould and Nissen‐Petersen 1
1999). In the United States adoption has been slower but is gaining ground, particularly in the southwest. Colorado changed its water laws in the spring of 2009 to allow rural residents who receive water from private wells to install rainwater harvesting systems, and the City of Santa Fe, New Mexico, now requires new homes to install rainwater harvesting systems(Johnson 2009). The use of rainwater harvesting systems is often overlooked by engineers and planners, generally because these systems often require added effort in the planning and development stages due the diffuse nature of these projects. A large rainwater harvesting project is often a combination of many smaller projects, such as collection tanks at individual homes, requiring the input from a broad spectrum of stakeholders. This can often be seen as a drawback to a project and a more traditional system may be selected to avoid perceived headaches the need for community involvement and consensus building. Rainwater collection can be divided into large, medium and small scale systems. Large scale systems include floodwater harvesting for crops or groundwater recharge. Collection from rock outcroppings or large impervious constructed surfaces may be considered medium scale projects. These projects could use small dams, sand rivers, or hafirs ‐ a type of in‐ground reservoir common in Sudan ‐ for storing water. Small scale systems are roofwater collection systems and small ground collection systems such as from a courtyard. Typically using cisterns or small 2
tanks for water storage(Gould and Nissen‐Petersen 1999). This paper will deal with roofwater systems used at the household level, examining in depth the Samoan village of Falelima’s ability to reliably meet the population’s domestic water needs through expanded use of these systems. A rainwater harvesting system has three main features: an area to collect runoff, a tank to store runoff, and a means to convey runoff from the collection point to the storage tank. The collection area can be any hard impervious surface. The increased use of corrugated metal roofing throughout the developing world provides an excellent existing surface for collection from which to begin a project. Metal roofing also has a high runoff coefficient, 0.8‐0.85, ensuring more water reaches the tank to become available for use(Cunliffe 1998). Cement or clay tile roofs also provide good collection areas but have lower runoff coefficients. Thatch or other organic roofing covered surfaces should not be used as they can add excess contamination to the water. Storage tanks used at the household scale can vary from 2m3 to greater than 20m3, depending on the systems purpose, climate, and the resources available to a family. Smaller tanks are suitable in regions with high levels of rainfall throughout the year or when used as a supplemental source during the wet season. Regions with distinct wet and dry seasons require tanks with large capacity if the purpose is to provide a constant supply year round. Tanks can be made of many materials and be 3
constructed above or below ground depending on preference and the availability of materials. Storage tanks should also have a means to withdraw water without contacting the water remaining in the tank, such as a tap located at the base of the tank. This reduces possibilities of contamination. The final component of a roofwater collection system is guttering to convey water from the roof to the storage tank. Gutters can be purchased or constructed using locally available materials. Gutters can often be overlooked when constructing a collection system. Time should be taken to ensure they are installed properly to ensure that the maximum amount of water reaches the storage tank. 2.0 Background Information for Samoa and Falelima This chapter will provide a brief overview of the Polynesian nation of Samoa, in general, and the village of Falelima, Savai’i. The rainwater harvesting project conducted by the author while serving as a Peace Corps Volunteer is also described briefly. 2.1 Geography and Environment Samoa consists of the eight western islands in the Samoan Island archipelago, formerly termed the Navigator Islands; the eastern islands form American Samoa. The islands are located in the south Pacific roughly, 8 degrees east of the 4
International Date Line and 13 degrees south of the Equator and approximately half way between Hawaii and New Zealand. See Figure 1. Samoa has a total area of 2,944 sq km, roughly three‐quarters the size of the state of Rhode Island. The climate is tropical with a rainy season from November to May. The interior of the main islands, Savai’i and Upolu, are volcanic mountains with dense jungle cover(CIA 2009). Figure 1 Map of Oceania. Samoa is marked by arrow. Source CIA World Fact Book 2009 2.2 National History In approximately 1000 BC, Polynesians settled the Samoan Islands. The first European to sight the islands was Dutchman Jacob Roggeveen in 1722. The first visit by a European, by French explorer Louis‐Antoine de Bougainville, occurred in 1768. 5
Contact with Samoa was limited until 1830, when missionary work began by John Williams of the London Missionary Society. The United States, Germany and Great Britain all showed interest in the Samoan Islands in the late 19th century and laid claims to the islands. All sides contributed supplies, training, and weapons to factions of the population. An expanded conflict seemed imminent in 1899 when all three nations sent warships to Apia harbor. A cyclone struck March 15th, damaging or destroying all three ships and ending the military conflict. In April the three nations agreed to a settlement in the Tripartite Convention of 1899. Under this convention the United States gained control of the eastern islands, which became American Samoa, and the Germans gained control of the western islands that form the present day Samoa. For relinquishing claims to the islands, the British received concessions from Germany in the Solomon Islands, Tonga and West Africa. Samoa remained a German territory until the outbreak of World War I in 1914. Following a request by the British the New Zealand Expeditionary Force landed on Upolu unopposed on August 29, 1914 to take control of territory which contained a German radio transmitter. Samoa remained under the control of New Zealand, first under a League of Nations mandate and then following World War II, as a United Nations Trust Territory. Formal opposition to New Zealand rule from native Samoans began in late 1926 with public meetings. In March of 1927 the Samoa League was formed declaring that it 6
was the duty of every person to “endeavor to procure through lawful means the alteration of any matter affecting the laws, government or constitution of the territory which may be considered prejudicial to the welfare and best interests of the people.” This group would become known as the Mau, which refers to a movement of people(Field 2006). In May 1961 under supervision of the United Nations, Samoa voted overwhelmingly for independence and in October the UN General assembly voted to end the trusteeship effective January 1, 1962. Western Samoa thus became the first Pacific nation to gain independence after colonization. In 1997 the constitution was amended, changing the nation’s name from Western Samoa to the Independent State of Samoa, commonly known as Samoa. Close ties remain between New Zealand and Samoa. 2.3 People and Culture Samoans are Polynesian in ancestry and are believed to have settled the islands around 1000 B.C. The 2006 census of Samoa puts the total population at 179,186. Approximately 21% of the population lives in or around the capital of Apia. The rural areas of Upolu contain 55%, and Savai’i accounts for 24% of the population (MOF 2007). 7
The population is very homogeneous, with Samoans and those of partial Samoan decent accounting for over 99% of the population. The country is also 98% Christian with the largest denominations being Congregationalist and Roman Catholic (CIA 2009). Religion plays an important role in the daily life of Samoa with many villages having an evening prayer period, or Sa, usually around sunset. 2.4 Water and Sanitation The UN Human Development Report 2007/2008 states access to an improved drinking water source in Samoa declined from 91% to 88% between 1990 and 2004, while access to improved sanitation increased from 98% to 100% over the same period(Watkins 2007). This is interesting in that global, access to drinking water is much greater than access to sanitation. The decrease in water access in Samoa is due to major cyclones that destroyed significant infrastructure in 1990 and 1991. The universal access to sanitation is most likely in part due to efforts of Peace Corps Volunteers. The first PCVs to serve in Samoa came in response to a cyclone in 1967 and served in the water and sanitation sector. Pit latrine toilet projects were implemented on a large scale across the country, and latrines are referred to as a “fale Pisikoa” or a Peace Corps house. The European Union has established the Water Sector Support Program (WASSP) in Samoa to assist in planning and development of water supply, sanitation and storm water management. The EU has committed over €20 million to water development 8
in Samoa to be used from 2004 to 2010(MOF 2006). The majority of funding has been used provided to the Samoa Water Authority (SWA). In 2008 the program expanded with the goal of assisting villages improve current independent piped water systems. 2.5 Falelima, Savai’i The village of Falelima is located on the northwest corner of Savai’i at the base of the Falealupo Peninsula. See Figure 2. This region of Samoa has extremely limited water resources available for two primary reasons. First, during the dry season rain typically comes from the southeast placing the region in the rain shadow of the island’s interior mountains. Second, the geological structure of the region is characterized by basalt lava flows which contain many joints, cracks, and faults allowing for high levels of infiltration effectively reducing ground runoff to near zero(Booth 2007). This ensures that there are no surface water sources in the region that can be tapped for supply and increases the risk of saline intrusion when ground water is pumped. The Village of Falelima and most of the Falealupo Peninsula are part of the 10% of Samoa that is not connected to any type of piped water distribution system. A previous piped water system existed but was destroyed by cyclones in 1990‐1991; remnants including a former storage tank and sections of pipe remain along the road. 9
Figure 2: Map of Samoa. Falelima marked with arrow. Source http://en.wikipedia.org/wiki/File:Samoa_Country_map.png used under the GNU Free Documentation License All fresh water used in Falelima is collected in rainwater harvesting systems; however, not all members of the community had this capability in 2006. In Falelima the ability to harvest rainwater varies greatly from family to family, with some having the capability to store in excess of 10 m3 for each member of the family and others with no storage capacity at all. Over 65% of the village of Falelima has less than the mean average per capita storage of 2.7 m3, (see Appendix A for data). Many of these families have large numbers of people sharing one medium tank or one or two small tanks. Nearly all families in the village faced the risk of running out of water during the dry season when rates above basic levels are used. Such an event can have major 10
impacts on the health of a family. Without adequate storage capacity, families are forced to make serious decisions about how they use water at these times often reducing the water they use for drinking, bathing and cleaning. Reductions in any of these categories can have serious health effects and allow for the spread of disease and illness if the reductions continue for even modest lengths of time. A partnership between the Samoan Water Authority (SWA), the Water Sector Support Program (WASSP), and the Ministry of Natural Resources and Environment (MNRE) is investigating options to expand the piped water distribution system at the north end of the district to communities that are not currently served. This current system provides water for two hours each morning and evening. There have also been issues with the salinity of the water pumped into this system. However, it is expected that it will be at least three to five years before implementation of such a system could begin due to the limited water in the region. The two sources that are most often considered feasible at this time are boreholes in the Falealupo area or surface waters in the Palauli area on the southern coast of Savai’i. Both of these sources come with significant questions as to their viability. There are significant doubts about the ability of boreholes to provide water without saline intrusion. Sourcing the water in Palauli would require pumping the water 40 miles over varied terrain. Either of these solutions would require large amounts of electricity on an island that uses only diesel power generators. 11
For these regions it is therefore important to continue to build rainwater harvesting tanks which continue to be used after the implementation of a piped system This will reduce the demand on the system by providing water for bathing, cleaning and toilet facilities, allowing the piped system to provide clean, high quality water for drinking and cooking. 2.6 GEF UNDP Grant Project The Falelima women’s committee applied for a planning grant through from the Global Environmental Facility (GEF) administered by the Samoa United Nations Development Program (UNDP) office, to investigate the possibility of protecting two coastal pools used primarily for bathing and laundry as a possible emergency water source. Protection was deemed unfeasible due to the location on the coast constantly allowing sea water into the pools. During a site visit by the UNDP, discussions turned to rainwater harvesting as a means of improving the water supply capabilities of the village. Representatives from the UNDP office felt that they could support a proposal for an implementation grant to expand the village rainwater harvesting abilities. These grants were to be submitted with a target value of WS$50,000 Tala ($19,230 USD). 12
The village sought the services of a local carpenter with extensive experience in tank construction. He provided two tank design options for the village: a larger (20m3) tank, or a smaller (13m3) tank. Due to the restriction on the amount of the grant, the village chose the smaller volume tank design to allow more families to receive benefits from the project. A proposal to purchase supplies for construction of thirty‐
four 13m3 ferrocement tanks was submitted and approved for funding in January 2008. The grant would purchase the necessary supplies, and the village would be responsible for in kind donations of labor, sand, gravel and food, as well as, be responsible to pay the carpenter’s wages of WS$150 Tala ($58 USD) to run the construction process. The cost per tank was approximately WS$1,400 Tala ($538 USD). The materials and costs for a tank are shown in Table 1. The families also receive one 5m section of gutter and a downspout with each tank to increase the collection area being used. 13
Table 1: Tank Materials and Costs Material
Unit Cost
WS$
Quantity
Per Tank
Cost WS$
Chicken Wire 6'x150'
1
$196.00
$196.00
Pig fence 3' x 50meter
1
$185.00
$185.00
$155.00
Plain Wire #8
1
$155.00
HardBoard 3/16"
0.25
$29.50
$7.38
Galv Nails 2" Lbs
1.5
$3.50
$5.25
Galv Nails 3" Lbs
1.5
$3.50
$5.25
Cement sacks 40 kg
23
$23.50
$540.50
Tank Tap 1/2"
1
$20.00
$20.00
Faucet Socket 1/2"
1
$1.50
$1.50
Gate Valve 3/4"
1
$20.00
$20.00
Valve Socket 3/4"
1
$2.00
$2.00
PVC Pipe 1/2"x10'
1
$9.00
$9.00
PVC Pipe 3/4"x10'
0.5
$15.00
$7.50
PVC Glue 236 ml
$6.00
0.5
$12.00
Seal Tape
1
$2.00
$2.00
Paint Brush 4"
2
$22.50
$45.00
Plastic Spouting 5 meter
1
$62.00
$62.00
Rainhead Outlet
1
$36.00
$36.00
Down Pipe 3meter
1
$38.00
$38.00
Spouting Bend 3"
1
$8.00
$8.00
Stop Ends (L & R)
2
$5.00
$10.00
External Brackets
6
$4.50
$27.00
Joiner
1
$13.00
$13.00
Total Cost
$1,401.38
Per Tank
Cost US$
$75.38
$71.15
$59.62
$2.84
$2.02
$2.02
$207.88
$7.69
$0.58
$7.69
$0.77
$3.46
$2.88
$2.31
$0.77
$17.31
$23.85
$13.85
$14.62
$3.08
$3.85
$10.38
$5.00
$538.99 The village women’s committee served as the guarantee on the project and assumed management responsibilities. The village families were ranked according to storage capacity per individual, and families with the lowest capacity were given first opportunity to receive a tank if they were able pay the carpenter’s fee. In the end most of the tanks went to families at the bottom end of the scale. However, a few tanks did go to families higher on the list. These families included pastors for various churches within the village and other important members of the community. The village allowed this in part due to the fact that these families often host village events, and in one case the family operates the village preschool at their home. 14
These factors where not taken into account by the ranking but still cause a drain on these families’ water resources. The construction of the tanks was completed in three phases. This allowed for oversight of the project by the UNDP office to ensure funds were used correctly. Each phase of construction lasted approximately two weeks. The carpenter and three assistants provided the technical skills required of the project, while village members provided manual labor. Before construction began at a household the family was required to prepare the site for construction and collect the sand and gravel required for construction. Each tank required approximately 8 hours of construction time spread over 4 days. On the first day the foundation was cast with pig fence used as reinforcement. The second day was construction of the tank walls using removable formwork of galvanized sheet metal supported by a wooden framework. Two layers of ferrocement were applied. The first layer was reinforced by 4 layer of chicken wire and a spiral of #8 steel wire, the foundation reinforcement was tied to the chicken wire. See Figure 3. Pig fence reinforcement was added before the application of the second layer. See Figure 4. The next day the wall formwork was removed and a skim coat was applied to the interior tank walls. Formwork was then constructed to support casting the tank roof, also using pig fence reinforcement. An access hole was left in each tank to allow for maintenance and removal of the formwork. On the final day all forms were removed, a final skim coat was applied to the tank exterior and the tank interior was 15
painted with a cement and water mix to reduce water seepage. The exterior was also given a rough texture to allow for better bonding should repairs be needed in the future. A finished tank is shown in Figure 5. Figure 3: Tank reinforcement on formwork Figure 4: Appling second ferrocement layer 16
Figure 5: Completed tank Upon completion of this project, all households in Falelima had a minimum of one ferrocement tank with a capacity of at least 13m3 for the collection of rainwater. The village continued to have great variation in per capita collection and storage capabilities among families. The next chapter will look more closely at how these discrepancies affect the level at which individual families can meet their water needs. 17
3.0 Methods and Data This chapter describes the data gathered to analyze the ability of Falelima, Samoa to meet its fresh water needs through rainwater harvesting and the methods by which that data was analyzed to make recommendations for improving water supply reliability. Data on collection area, storage tank capacity, and number of occupants was collected during a house to house survey of the village. These data were normalized for comparison by ranking collection area and storage volume per individual. 3.1 Precipitation A region’s precipitation plays the controlling factor in designing rainwater harvesting systems and analyzing the ineffectiveness. Both the total annual rainfall and the distribution of that rainfall throughout the year must be considered in the evaluation and design of a rainwater collection system. Due to the inherent variability of rainfall patterns, a long term record of rainfall (ten years or more) is recommended for use in designing a harvesting system. While this is often easily obtainable in developed nations, it is much less likely to exist in a developing nation, or it may only be available for the capital or a large population center. This data may or may not reflect the conditions in a rural village and should be evaluated to determine its usefulness. 18
As a tropical south Pacific island, Samoa receives in an average of 3,000 mm of rainfall each year; however this can vary greatly across the islands. The islands also experience a cycle of wet and dry seasons. The wet season, November to April, can account for up to 75% of annual rainfall (SOPAC 2007). Falelima, located on the northwest corner of Savai’i, sees a very distinct change between wet and dry seasons. This is due to dry season winds primarily originating in the southeast which cause rainfall on the southern portion of the island (as rain clouds reach the central ridgeline of the island) but dry conditions exist due to a rain shadow on the northern portion of the island. In January 2006, Samoa’s Ministry of Natural Resources Department of Meteorology (MET) installed a daily rainfall monitoring gauge in Falelima. Data records begin January 25th, 2006 and data from this gauge was the primary source of rainfall data for this project. The data used is from January 25, 2006 to December 31, 2008. The data was purchased from the MET office at Mulinu’u, Apia, Samoa. This provides a data record that is much shorter than would be considered optimal. An attempt was made to retrieve the extended record for rainfall from the village of Asau located approximately 15 miles to the north. The Asau records however are not from an automated gage. The record at Asau, while spanning a longer timeframe, contains large gaps in the data due to lack of personnel. 19
A second problem exists with the available data for Falelima in that 2006 was felt by many locals, both in the village and throughout the country, to be an extremely wet year. Table 2 shows recorded rainfall totals for 2006 – 2008 in Falelima; daily records are in Appendix B. The 2006 total is more than 35% greater than the 2008 total and does not include January 1st to 25th, which is typically one of the wettest months in Samoa. The longest period without rain in the record occurs from July 17 to August 15, 2008, which is followed by only 3 rain days before September 1. During this period tanks were observed to go dry. Table 2: Recorded Annual Rainfall in Falelima, Samoa Year
2006*
2007
2008
Rainfall
(mm)
4357
3687
3190
*2006 record begins January 26th. Rainfall may also be affected by events such as El Nino/Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), and climate change. ENSO and PDO events may cause interannual or interdecadal climate oscillations that effect annual rainfall and the reliability of rainwater harvesting systems. The central Pacific could see reductions in rainfall and a rise of sea level, leading to greater saline intrusion into ground water, due to climate change. When combined these effects compound the threats to the region’s water resources (Mimura et al. 2007). The effects of these events on Samoa should be investigated in future work. 20
3.2 Collection Area In Samoa rainwater is collected from the roofs of houses and other buildings such as schools and churches and used on the sites where it is collected. Occasionally roof areas are found that have been constructed for the sole purpose of collecting rainwater. Rough dimensions of all available corrugated metal roofing areas were collected for each family compound by pacing off the structures. This often included multiple structures on each compound. Structures with thatch roofing were not considered because thatch can add contaminants to the water supply and have a lower runoff coefficient. Collection from thatch roofing was not found to occur, and villagers did not consider it to be a proper collection source. The total area available to each family for collection ranged from 27m2 to 568m2. Families with larger roof area often had greater numbers of members, causing per capita roof area to range from 1m2 to 114m2. Plastic guttering was used by most families to collect rainwater and divert it into storage tanks; however, some homemade gutters were also used. Few families collected from 100% of their available roof area, and these families were often at the lower end of the range of available area. Due to the irregular shape of most structures, an estimate of the area being collected was made. 21
3.3 Water Storage Prior to the project in Falelima, there was great variability in the ability of each family to store collected rainwater. Total storage capacity for families ranged from 0 liters to 64,300 liters, and storage per capita for families ranged from 0 liters per capita to 12,000 liters per capita. The village primarily uses large ferrocement tanks for storage, with tanks ranging in size from 10 m3 to 20 m3. These tanks have been built on site with funding from various aid agencies, including the European Union, JICA and most recently with UNDP and GEF support (this project). Most families have one or two tanks in this size range. These tanks are built on site with the assistance of a local carpenter from a neighboring village. Smaller, cube‐shaped cement tanks approximately 2.5 m3 in volume are also commonly found. From discussions with villagers, these tanks appear to have been mass produced in response to the 1990 and 1991 cyclones that did considerable damage to the nation. Many of these small tanks are now used to supply water for a family’s toilet. Many of these smaller tanks show significant signs of aging, with exposed reinforcement that is rapidly deteriorating in the tropical climate and broken taps. 22
Plastic tanks are available and manufactured in Samoa. They appear to be becoming more popular and are often added to building projects funded by international agencies. Plastic tanks are found in Falelima at the primary school and the women’s committee meeting house constructed in early 2007. Plastic tanks, however, remain very expensive when compared to ferrocement tanks built on site. A 5,000 l plastic tank cost WS$3,169 Tala ($1,218 USD) not including tap fittings and materials for a foundation slab. This is nearly five times the cost for an equivalent capacity as the 13m3 tanks built with GEF funding. Village members also commented that ferrocement tanks where preferable because water stored inside them remains cooler, an important factor in the tropics. The village also has one corrugated metal tank at the Assembly of God church. Many families also used open 200 L drums to collect runoff. The volume of these barrels was not included in a family’s storage capacity due to it being considered an unimproved method of storage that does not meet the requirements for protecting stored rainwater. Collection in large pots and wash tubs during storms is also a common occurrence, with the water often used for cleaning or laundry at the time of collection. 3.4 Water Demand The quantity of water used by individuals each day varies greatly around the world from less than 5 liters to greater than 1,000 liters. In the northwest region of the 23
island of Upolu where residents use a metered piped water supply system residents consumption rates exceed 300 l/c/d(MOF 2006). This level of service is not feasible using rainwater harvesting. At approximately 20 liters per capita per day, minimum water needs begin to be met (Gould and Nissen‐Petersen 1999). The World Health Organization has defined levels of water service at which water needs for consumption and hygiene are met, as shown in Table 3 (Howard and Bartram 2003). For Falelima, analysis was run to determine the ability to meet or exceed basic and intermediate levels of service (20, 50, and 70 l/c/d). Rainwater harvesting at the household level is an onsite supply which would be considered intermediate access. Table 3: WHO Water Service level definitions Service
Level
Ave. quantity
collected
l/c/d
Access
Consumption
Hygiene
Health
Risk
No Access
<5
>30 min.
collection
Needs not
assured
Not possible
Very
High
Basic
Access
20
5 - 30 min
collection
Should be
assured
Basic hygiene possible
Bathing laundry difficult
High
Intermediate
access
50
1 tap on site or
<5min collection
time
Assured
Basic hygiene assured
Bathing laundry possible
Low
Optimal
access
>100
Multiple taps on
site
All needs met
All needs met
Very Low
The 2001 census lists a population of 424, while village surveys conducted during this investigation found a village population of 545 members. This discrepancy can be attributed at least partially to the mobility of the population. It is not uncommon for people to move from one family home to another following work or school. For this study a population of 545 will be used to provide greater assurance that results 24
will meet minimum needs. This number is broken down among households as required for this study. Water quality was not investigated in this study; however rainwater is generally free of pollutants as it falls on a collection surface. Micro‐organisms represent the greatest risk to most systems due to contamination from leaf litter or animal droppings carried from the collection surface into the tank. A proper maintenance program can reduce the risk of contamination from these sources (Cunliffe 1998). An analysis of water quality could be investigated in future work. 3.5 Rainwater Harvesting Model The effectiveness of household rainwater harvesting for Falelima was modeled using an Excel© spreadsheet. This model was supplied by Clive Carpenter a consultant to the WaSSP. The model uses daily rainfall data and six parameters to calculate the reliability and demand satisfaction of a given rainwater harvesting system, and output includes a graph of the system’s storage tank level over the simulation time period. The model assumes that a family’s collection systems runs as a single unit combining all tank volumes and collection areas and that water withdrawals are made equally from all tanks. The parameters of tank volume, roof area and family size are all independent variables specific to each family. Gutter factor indicates the percentage of roof area collected where 1.0 = full collection. Values for these variables were determined by the village survey. The initial tank 25
level was set at zero. In late January when the rainfall record begins tanks would not be empty however; to standardize the model inputs this was selected. A large rainfall occurs on the second day of the record that can meet most demand scenarios modeled. Water demand rates were selected based on WHO water service level definitions. Galvanized, corrugated roofing was the material for collection areas which has runoff coefficients in the range of 0.8 to 0.85. A runoff coefficient of 0.85 was used because of the high level of annual rainfall. The rationing level is the percentage of tank storage below which rationing would occur. The rationing factor is the percentage of water demand used while rationing is occurring. For the initial analysis, rationing was not considered. These variables are useful when creating a water use plan for a specific family. A family with greater storage capacity could begin rationing at a lower level. The rationing factor can be set to ensure that a minimum service level is achieved. Table 4: Model Parameters Parameter
Tank Volume
Initial Tank Level
Roof Area
Family Size
Units
l
l
m2
#
Water Demand
l/cap/d
Runoff
Coefficient
Gutter Factor
Rationing Level
Rationing Factor
Value(s)
Varied
0
Varied
Varied
20, 50,
70
#
0.85
#
l
#
0-1
0-1
0-1
For each day the model first calculates runoff as R = P x A x cr R = Runoff (liters) 26
P = Precipitation (mm) A = Roof Area (m2) cr = Runoff Coefficient Second, storage tank overflow is determined by adding the runoff to the storage at the end of the previous day and comparing this to the tank volume; if greater, the storage level is set equal to the tank volume, and overflow is computed as the excess amount: Overflow = Max(0, Storage(t‐1) + Runoff(t) – Tank Volume). The model then calculates the daily water use for the household. First the storage volume in the tank is compared to the level at which rationing occurs. If greater, then no rationing occurs and the model computes water use by multiplying the number of residents by the (target) daily per capita water demand. If rationing does occur, then use is computed by multiplying the demand by a rationing factor. The use is then subtracted from the water available to determine the final storage volume in the tank for the day. If the demand is greater than the available water, the stored volume is set to zero. The model then checks to ensure that the supply met the demand (with or without rationing). If the demand is not met, the day is marked as a dry day. Model outputs include the length of record in years; the system’s satisfaction of demand, calculated as the percentage of demand that is met; the system reliability, determined as the percentage of days where demand is met; and the longest dry 27
spell, computed as the largest number of consecutive days in which demand was not met. The model also produces a graph showing the daily volume of water stored in the tank over the course of the record. Table 5: Model Results Result
Length of record
Satisfaction
Reliability
Longest dry spell
unit
years
%
%
days
Model example The following is an example of how the model represents a household rainwater harvesting system. Family 40, where the author lived as a Peace Corps Volunteer from August 2006 to September 2008, will be used. This household lies approximately in the middle of the range for the village with respect to per capita storage capacity and collection area. The parameters for the household are given in Table 6, as taken from the village survey. (Parameters for all households can be found in Appendix A.) For this example a steady demand of 50 l/c/d, with no rationing, is assumed. The first several rows of calculations are shown in Table 7. Table 6: Model Parameters for Household 40 Parameter
unit
Value
Tank Volume
Initial Tank Level
Roof Area
Number of People
Water Demand
Runoff Coefficient
Gutter Factor
Rationing Level
Rationing Factor
l
l
m2
#
l/cap/d
#
#
l
#
38600
0
187
11
50
0.85
0.508
na
na
28
Run of Dry
Days
Demand
Met
Supply (l)
Storage Demand (l)
Demand (l)
Overflow
(l)
Storage
After
Overflow
(l)
Storage+R
unoff (l)
Runoff (l)
Rain (mm)
Date
Table 7: Initial model calculations for Family 40 household 1/26/06
64.8
5230
5230
0
5230
550
4680 550
1
0
1/27/06
28.7
2318
6998
0
6998
550
6448 550
1
0
1/28/06
33.5
2707
9155
0
9155
550
8605 550
1
0
1/29/06
31.8
2564
11169
0
11169
550
10619 550
1
0
1/30/06
62.7
5066
15684
0
15684
550
15134 550
1
0
1/31/06
114.8
9270
24405
0
24405
550
23855 550
1
0
2/1/06
167.6 13536
37391
0
37391
550
36841 550
1
0
2/2/06
137.2 11075
47916 9316
38600
550
38050 550
1
0
41967 3367
38600
550
38050 550
1
0 2/3/06
48.5
3917
Based on the assumed parameters, the model finds that the household system has a 92% reliability at producing 50 l/c/d over the available rainfall record (2006‐2008). This means that over the course of nearly 3 years there are only 85 days when the demand is not met. The satisfaction rate is slightly higher because it accounts for days when a portion of demand is met. The longest period in which the system does not meet demand is approximately one month. Model outputs are shown in Table 8, and Figure 6 charts the daily volume of water in the storage tank over the three‐
year period. Table 8: Results for model of Family 40 household Length of
record
Satisfaction
Reliability
Longest dry
spell
2.93 yr
93.18%
92.06%
32 days
29
40,000
35,000
Tank Volume (litres)
30,000
25,000
20,000
15,000
10,000
5,000
Dec-08
Oct-08
Nov-08
Sep-08
Jul-08
Aug-08
Jun-08
Apr-08
May-08
Mar-08
Jan-08
Feb-08
Dec-07
Oct-07
Nov-07
Sep-07
Jul-07
Aug-07
Jun-07
Apr-07
May-07
Jan-07
Feb-07
Mar-07
Dec-06
Oct-06
Nov-06
Sep-06
Jul-06
Aug-06
Jun-06
Apr-06
May-06
Jan-06
Feb-06
Mar-06
0
Date
Figure 6: Modeled daily water storage at Family 40 household The figure shows how the storage tanks are filled during the wet season each year, beginning around November. As the dry season begins around June, storage volumes are depleted with little recharge. This model shows how, for a constant demand of 50 l/c/d, this system will fail before the steady rains of the wet season return. In reality, the family does reduce demand during the dry season as the tank level drops, mostly by reducing laundry and bathing in the ocean. A rationing system where demand is halved once the volume of stored water reaches 30% of the capacity would provide at least basic access over the course of the rainfall record. The daily water storage for this rationing scenario is shown in Figure 7. 30
40,000
35,000
Tank Volume (litres)
30,000
25,000
20,000
15,000
10,000
5,000
Dec-08
Oct-08
Nov-08
Sep-08
Jul-08
Aug-08
Jun-08
Apr-08
May-08
Mar-08
Jan-08
Feb-08
Dec-07
Oct-07
Nov-07
Sep-07
Jul-07
Aug-07
Jun-07
Apr-07
May-07
Jan-07
Feb-07
Mar-07
Dec-06
Oct-06
Nov-06
Sep-06
Jul-06
Aug-06
Jun-06
Apr-06
May-06
Jan-06
Feb-06
Mar-06
0
Date
Figure 7: Modeled daily water storage at Family 40 household with rationing 4.0 Results and Discussion The model was used to investigate the requirements needed to meet three levels of demand for Falelima. The World Health Organization basic and intermediate access levels of 20l/c/d and 50l/c/d were selected, as well as a rate of 70 l/c/d. Preliminary investigations showed that the optimum access level of 100 l/c/d was well beyond the level of collection currently available. 4.1 Design Curve Using this model, design curves were produced to show the relationship between required tank storage volume collection area for a given water demand and 31
reliability (or demand satisfaction) based on a given rainfall pattern. This was done by adjusting the collection area while holding the tank volume fixed until the point at which reliability reached 100% was found for a given demand. This was then repeated for different tank volumes to produce the design curves. Figure 8 shows curves for indicating combinations of tank volume and roof areas that will provide 50 liters to an individual every day (100% reliability), based on the daily rainfall for 3 years . This shows that the 2007 pattern controls the design curve for intermediate values of tank volume and collection area, but the 2008 pattern controls for more extreme values. The extremely wet year of 2006 never controls the design curves. This pattern was found to hold true for all three levels of demand investigated. 40
Collection Area m
2
35
30
2006
2007
2008
25
20
15
10
5
0
0
1000
2000
3000
4000
5000
6000
7000
Tank Volume L
Figure 8: 50 l/c/d curves for years 2006 – 2008. Figure shows tank volume and collection area required to provide 50 l/c/d with 100% reliability, based on 3 annual rainfall patterns. 32
The curves were then combined to create a design curve for each level of demand. See Figure 9. 40
Collection Area m
2
35
20 L/c/d
50 L/c/d
70 L/c/d
30
25
20
15
10
5
0
0
1000
2000
3000
4000
Tank Volume L
5000
6000
7000
8000
Figure 9: Design Curves for Falelima, Samoa (100% reliability) Using this same process curves for reliability levels of 99%, 95%, and 90% were also produced for the water demand levels of 50 and 70 l/c/d. See Figure 10. These reliability rates represent approximately 4, 18, and 36 days per year where demand is not met. 33
50
70 l/c/d 100%
45
70 l/c/d 99%
70 l/c/d 95%
40
2
Collection Area (m )
70 l/c/d 90%
35
50 l/c/d 100%
50 l/c/d 99%
30
50 l/c/d 95%
50 l/c/d 90%
25
20 l/c/d 100%
20
15
10
5
0
0
1000
2000
3000
4000
5000
6000
7000
8000
Tank Volume (l)
Figure 10: Demand curves for various reliability rates. 4.2 Meeting Basic Access Requirements For each household, tank volume available and collection area being used were normalized for the number of individuals living there. These values were then plotted against the design curves to determine the initial conditions of the village. See Figure 11. 34
40
35
20 L/c/d
50 L/c/d
70 L/c/d
Families Initial
Collection Area m 2
30
25
20
15
10
5
0
0
1000
2000
3000
4000
5000
6000
Tank Volume L
Figure 11: Families initial per capita ability for water supply 7000
8000
The water tank project undertaken by the village resulted in the construction of 34 tanks with a capacity of 13,000 liters each. A 5‐meter section of guttering was provided with each tank. This gutter added between 10 m2 and 35 m2 of collection area to each household, with the exception of one house that was already fully guttered. Figure 12 shows the state of the village at the completion of the construction. Table 9 lists the number of families that fell into each range of access before and after the project. 35
50
45
20 L/c/d
50 L/c/d
70 L/c/d
Families After Project
40
Collection Area m 2
35
30
25
20
15
10
5
0
0
2000
4000
6000
8000
10000
12000
14000
16000
Tank Volume L
Figure 12: Village at the completion of tank construction. Table 9: Families in each range of daily water supply before and after the water project. Supply
<20
l/c/d
20 l/c/d
- 50
l/c/d
50 l/c/d
- 70
l/c/d
>70
l/c/d
#
Families
Before
Project
# Families
After
Project
18
6
29
35
9
11
6
10
The project left six families below the basic level of access. Two families did not participate in the project. Five families are large, with at least nine members, so when the benefits of the project were normalized per capita, they saw less improvement. Two of these families also started out without any rainwater 36
harvesting capacity, and one had only a small area for collection that was already being fully utilized. Table 10 lists the families not exceeding the 20l/c/d design curve, along with the collection area required to meet their need. Table 10: Families not exceeding basic water access of 20l/c/d Area
Available
2
m
Area
Collected
m2
Area
Need for
20 l/c/d
m2
Household
Members
Total
Storage l
2
16
13,000
71
17
317
3
9
13,000
107
30
52
5
19
30,100
43
32
96
6
10
22,900
11
11
31
20
10
18,400
55
15
40
30
6
13,900
33
15
19
Notes
Started
without
Collection
Started
without
Collection
Full
collection
area in use
Did not
Participate
in Project
Did not
Participate
in Project
Three of the families could meet the requirements for basic access by expanding the guttering on roofing they already possess. Three could not exceed the required area with their current roof area. Families 5 and 6 could complete the guttering on the existing area and add additional roofing to meet their needs. Family 2 currently has less than 1 m3 of storage for each family member. To meet the goal of basic access levels, an unreasonable amount of roof area would need to be added and would still leave the family at an extreme end of the design curve. For this family the addition of a second tank, guttering to the existing roof and 8 m2 of new guttered collection area will allow them to achieve basic access. Cost estimates for these solutions are shown in Table 11. 37
Table 11: Possible solutions for families not exceeding 20 l/c/d. Family
Solution
Estimated
Cost
2
Construct second tank,
complete guttering and 8 m2
collection area
WS$2,250
USD$865
3
Add gutter to existing roof
WS$370
USD$142
6
Complete guttering and
construct 50 m2 of guttered
area
Construct 16 m2 of additional
guttered collection area
20
Add gutter to existing roof
30
Add gutter to existing roof
5
WS$1,250
USD$480
WS$550
USD$212
WS$340
USD$130
WS$150
USD$58
4.3 Using Variable Demand Levels The demand models have been used to investigate requirements of meeting a basic supply of water throughout the year at a constant rate. During the wet season all systems experience overflow. If a family monitors their tank level closely demands can often be significantly increased for portions of the year. This would require active monitoring by the family but could be done particularly during the wet season when the risk of tanks running dry is reduced. 5.0 Conclusions and Recommendations The use of rainwater harvesting is widespread throughout the Falealupo Peninsula area of Samoa, where no piped water system exists to meet the needs of population and the construction of such a system faces serious challenges. The ability of 38
rainwater harvesting to meet the water demands of families is shown to be possible by the model and by its successful use by large number of families in the area. The expanded uses of rainwater harvesting in the region would not require the addition of new technology but could build on the knowledge base currently held by the communities of the region regarding system maintenance and use. Lack of knowledge regarding how a technology operates is often a contributing factor to the failure of development projects and by not introducing a new technology, this concern does not arise. This solution also does not require power for its operation or maintenance. Given limited budgets for water projects, the use of funds should be optimized for increasing access at the household level. This model can help the user to understand relationships among roof collection area, tank storage volume, and reliability, and thus make more efficient use of limited funds. The greatest weakness currently in using the model as described here for the region is in the current lack of useable data. As each additional year of data is made available the design curves can be updated to ensure that reliability levels are accurate and the rainfall patterns used represent real patterns over time. Efforts should also be made to investigate the effects of El Nino/Southern Oscillation (ENSO) and Pacific Decadal Oscillation events and climate change on the total annual precipitation and seasonal precipitation patterns. 39
If a piped water system is developed for the region in the future, rainwater tanks will still be a valuable resource. With available resources, a water quality study could be done to compare the quality of tank water with that of piped water supplies and with international drinking water standards. A piped water system could supply water for consumption and other activities that require high quality water while tanks could be used to provide water for cleaning, toilets, or gardening. This would reduce the demands on a piped system reducing the energy cost of operation and help to reduce the concern of saline intrusion if boreholes are used. 40
References Booth, S. (2007). Samoa Technical Note: Hydrogeological mission to Savai'i. EU‐SOPAC Project Report 79 ‐ Booth. Suva, Fiji, SOPAC. CIA. (2009). "World Factbook." Retrieved 6/15/09, 2009, from https://www.cia.gov/library/publications/the‐world‐factbook/geos/ws.html. Cunliffe, D. A. (1998). Guidence on the use of Rainwater Tanks. D. o. H. Services. Australia, National Environmental Health Forum. Field, M. (2006). Black Saturday : New Zealand's tragic blunders in Samoa. Auckland [N.Z.], Reed. Gould, J. and E. Nissen‐Petersen (1999). Rainwater catchment systems for domestic supply : design, construction and implementation. London, Intermediate Technology Publications. Howard, G. and Bartram (2003). Domestic Water Quantity, Service, Level and Health, WHO. Johnson, K. (2009). It’s Now Legal to Catch a Raindrop in Colorado The New York Times. DURANGO, Colo., The New York Times Company. Mimura, N., L. Nurse, R.F. McLean, J. Agard, L. Briguglio, P. Lefale, R. Payet and G. Sem (2007). Small islands. Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, UK, Cambridge University Press. MOF (2006). Water for Life Sector Plan Update, Samoa Ministry of Finance. MOF (2007). TUSIGAIGOA O TAGATA MA FALE 2006. Apia, Samoa, Ministry of Finance. SOPAC (2007). National Interrated Water Resource Management Diagnostic Report Samoa, SOPAC. UNICEF (2008). Progress on drinking water and sanitation : special focus on sanitation. New York, NY Geneva, Unicef ; World Health Organization. Watkins, K. (2007). Human Development Report 2007/2008. New york, NY, UNDP. 41
13.0
13.0
13.0
16.4
30.1
22.9
19.8
19.8
31.8
29.1
24.3
36.7
27.8
16.4
16.4
32.5
34.3
29.3
33.0
18.4
26.0
31.8
33.7
15.4
45.5
50.6
3250 17 813 17 1444 30 2048 28 1582 32 2289 11 3292 54 3292 69 2269 43 2424 52 3043 48 2292 52 3093 47 8190 39 8190 85 2954 65 2856 115 3258 33 2997 74 1842 15 1856 63 3180 68 3065 97 1924 31 2846 89 2809 59 Final Area Collected per Capita (m2/cap) 0.0
0.0
0.0
14.2
24.5
11.1
32.9
39.1
24.6
27.6
13.4
21.0
17.6
8.3
29.6
25.4
53.6
15.4
27.0
8.1
33.9
22.9
32.9
16.1
33.9
16.3
Final Area Collected (m2) Final Storage per Capita (l/c) 0
0%
0
0%
0
0%
6 22%
22 51%
11 100%
37 20%
44 35%
33 60%
37 36%
19 12%
31 38%
29 26%
14 17%
50 56%
45 36%
95 61%
28 85%
49 36%
15 27%
63 66%
43 46%
62 32%
31 54%
69 48%
34 24%
Final Total Storage (m3) 55
71
107
27
43
11
185
124
55
103
164
82
110
82
89
124
155
33
137
55
96
93
196
57
144
144
Initial Area Collected per Capita (m2/cap) 0.0 0.0 0.0 0.4 0.9 1.0 1.1 1.1 1.3 1.3 1.4 1.5 1.6 1.7 1.7 1.8 1.8 1.8 1.8 1.8 1.9 1.9 1.9 1.9 2.0 2.1 % Area Collected 0.0 0.0 0.0 3.4 17.1 9.9 6.8 6.8 18.8 16.1 11.3 23.7 14.8 3.4 3.4 19.5 21.3 16.3 20.0 18.4 26.0 18.8 20.7 15.4 32.5 37.6 Initial Area Collected (m2) Initial Storage (m3) 4 16 9 8 19 10 6 6 14 12 8 16 9 2 2 11 12 9 11 10 14 10 11 8 16 18 Total Roof Area (m2) Family Size 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Initial Storage per Capita (m3/c) Household ID Appendix A: Village Data 4.3 1.1 3.3 3.5 1.7 1.1 9.0 11.5 3.1 4.3 6.0 3.3 5.2 19.5 42.5 5.9 9.6 3.7 6.7 1.5 4.5 6.8 8.8 3.9 5.6 3.3 42
Final Storage per Capita (l/c) 26.2
16.1
17.5
6.5
24.9
24.8
10.0
23.8
14.9
28.0
17.7
26.3
12.3
27.1
25.0
14.4
25.3
6.8
11.8
27.0
10.6
14.6
51.3
4.1
11.1
6.7
10.8
10.4
10.4
11.3
14.7
19.6
18.3
13.9
22.1
35.1
22.5
25.6
20.4
28.3
28.6
21.3
40.7
38.6
49.0
36.7
38.8
33.0
53.5
32.6
17.0
34.6
48.4
32.8
47.2
16.2
33.4
17.2
28.9
48.4
2097 55 2179 35 2284 40 2323 15 2454 61 3904 76 2498 25 5118 75 2545 38 2570 72 2602 46 3039 80 4522 59 3505 95 4897 110 3671 53 3876 98 6590 57 5354 65 4069 110 4260 45 4328 63 6054 262 4687 19 6741 84 5413 36 5565 60 5747 60 5772 60 8072 92 Final Area Collected per Capita (m2/cap) Final Total Storage (m3) 103 55 53%
88 35 40%
79 40 51%
33 15 45%
106 61 58%
217 61 28%
55 25 45%
164 60 37%
50 38 76%
187 72 39%
66 46 70%
128 80 63%
110 38 35%
187 95 51%
293 90 31%
164 53 32%
308 98 32%
162 27 17%
202 48 24%
151 110 73%
115 45 39%
220 63 29%
738 227 31%
202 19
9%
187 54 29%
133 36 27%
250 60 24%
196 60 31%
82 60 73%
165 67 41%
Final Area Collected (m2) Initial Area Collected per Capita (m2/cap) 2.1 2.2 2.3 2.3 2.5 2.5 2.5 2.5 2.5 2.6 2.6 3.0 3.1 3.5 3.6 3.7 3.9 4.0 4.1 4.1 4.3 4.3 4.4 4.7 4.9 5.4 5.6 5.7 5.8 5.9 % Area Collected 14.7 19.6 18.3 13.9 22.1 22.1 22.5 12.6 20.4 28.3 28.6 21.3 27.7 38.6 36.0 36.7 38.8 20.0 40.5 32.6 17.0 34.6 35.4 32.8 34.2 16.2 33.4 17.2 28.9 35.4 Initial Area Collected (m2) Initial Storage (m3) 7 9 8 6 9 9 9 5 8 11 11 7 9 11 10 10 10 5 10 8 4 8 8 7 7 3 6 3 5 6 Total Roof Area (m2) Family Size 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 Initial Storage per Capita (m3/c) Household ID 7.9 3.9 5.0 2.5 6.8 8.4 2.8 15.0 4.8 6.5 4.2 11.4 6.6 8.6 11.0 5.3 9.8 11.4 6.5 13.8 11.3 7.9 32.8 2.7 12.0 12.0 10.0 20.0 12.0 15.3 43
12.9
13.6
33.2
13.2
13.9
7.2
14.2
18.8
53.6
0
49.5 6189 80 31.3 6256 85 41.5 6920 230 62.6 6958 92 64.3 8033 112 47.7 11915 82 72.9 14578 190 31.2 4201 67 72.9 14578 262 13.0 812.5 11 Final Area Collected per Capita (m2/cap) Final Area Collected (m2) Final Storage per Capita (l/c) 80 35%
85 40%
230 88%
92 37%
112 38%
62 40%
170 30%
56 40%
230 100%
0
0%
Final Total Storage (m3) 226
210
260
250
293
155
568
153
738
11
Initial Area Collected per Capita (m2/cap) Initial Area Collected (m2) 6.2 6.3 6.9 7.0 8.0 8.7 12.0 3.2 12.0 0 % Area Collected Total Roof Area (m2) 49.5 31.3 41.5 62.6 64.3 34.7 59.9 24 64 0 Initial Storage per Capita (m3/c) 57 8 58 5 59 6 60 9 61 8 62 4 63 5 Ave 8.7 Min 19 Max 2 Initial Storage (m3) Family Size Household ID 10.0 17.0 38.3 10.2 14.0 20.5 38.0 9.8 42.5 1.1 44
Appendix B: Falelima, Samoa Rainfall Data (measurements in mm) FALELIMA SAVAII
DAILY RAINFALL
Station #: 76019
District;
Location;
0
13 29' 11" SOUTH
Height Above MSL.
0
172 28' 46" WEST.
12m.
SAV76010 (begin date: UNKNOWN)
DAY
JAN
YEAR
2006
OCT
NOV
DEC
27.9
0.0
4.3
47.5
0.0
26.7
0.0
16.5
0.0
0.3
0.0
0.0
8.9
0.0
0.0
15.2
0.0
49.3
6.4
0.0
31.8
12.4
0.0
0.0
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
1
167.6
7.6
0.0
1.0
0.0
0.0
0.0
2
137.2
4.1
0.0
0.5
0.0
0.0
0.0
3
48.5
13.2
2.5
1.3
0.0
0.0
4
46.2
0.0
3.8
0.3
0.5
0.0
5
101.6
0.0
0.0
0.0
0.5
0.0
0.0
3.8
6
115.3
106.7
10.7
0.0
0.0
0.0
0.5
7.1
7
44.5
0.0
8.9
1.3
0.3
0.0
0.0
0.0
0.0
6.4
0.0
8
124.7
1.5
41.1
0.8
0.0
0.0
0.0
0.0
0.0
0.0
0.0
9
125.7
2.8
84.1
3.8
0.0
0.0
4.3
0.0
33.5
0.0
2.5
10
89.4
0.0
18.3
5.1
0.0
0.0
0.0
1.3
1.3
0.0
28.7
11
48.3
45.5
0.5
0.3
0.0
0.0
6.6
3.8
0.5
0.8
33.8
12
89.4
25.9
0.3
3.8
9.1
0.3
3.8
7.6
0.3
9.4
34.8
13
47.5
55.9
3.8
7.9
0.0
0.3
6.4
0.0
1.0
14.7
7.6
14
0.5
5.1
11.7
16.5
3.8
2.8
0.0
0.0
0.5
11.7
3.0
15
12.7
9.7
33.3
92.7
0.0
2.3
0.0
0.0
0.0
23.4
8.1
16
0.0
11.7
6.6
23.9
0.0
1.5
0.0
0.0
28.2
55.9
3.3
17
37.1
0.0
0.0
39.4
0.3
21.1
0.5
0.0
0.0
54.9
11.4
18
53.8
0.0
0.0
5.6
0.0
16.0
2.5
0.0
0.0
33.0
10.2
19
16.0
22.6
0.0
3.8
0.0
3.8
0.0
0.0
0.0
26.7
18.3
20
7.9
1.8
0.0
5.6
0.0
19.1
0.0
0.0
0.0
51.8
27.9
21
2.3
0.0
2.3
1.3
0.0
5.3
0.0
35.1
0.0
6.9
31.2
22
42.7
96.5
3.6
2.5
0.0
0.0
0.0
3.8
0.0
3.8
0.0
23
17.0
1.3
0.8
0.0
17.8
0.0
0.0
11.9
0.0
3.0
0.0
24
0.0
0.0
1.3
36.8
17.3
0.0
0.0
0.0
103.9
1.5
87.9
25
4.1
0.8
3.3
0.5
2.5
13.2
0.0
0.3
1.0
4.3
0.0
9.1
26
64.8
0.0
16.5
16.5
0.0
0.0
30.5
0.0
0.0
0.0
6.1
27
28.7
0.3
44.2
1.3
0.0
0.0
6.9
0.0
8.9
0.0
0.0
0.0
28
33.5
14.2
0.0
3.0
0.0
0.0
0.0
0.0
14.0
0.0
0.0
3.3
29
31.8
0.0
0.9
1.0
0.0
0.0
0.0
0.5
10.2
0.0
73.2
0.0
30
62.7
0.0
36.8
5.3
0.0
0.0
0.0
18.3
0.0
0.0
0.0
30.5
31
114.81
0.0
39.4
0.0
0.0
0.0
3.6
4.3
27.9
0.0
0.0
39.1
Total
336.3
1394.5
550.3
263.9
254.5
52.1
126.5
47.8
163.8
230.9
391.7
544.8
Mean
56.0
45.0
17.8
8.5
8.2
1.7
4.1
1.5
5.3
7.4
12.6
17.6
Raindays
6
25
22
23
22
9
14
10
15
13
19
23
45
FALELIMA SAVAII
DAILY RAINFALL
Station #: 76019
District;
0
13 29' 11" SOUTH
Location;
Height Above MSL.
0
172 28' 46" WEST.
12m.
SAV76010 (begin date: UNKNOWN)
YEAR
2007
DAY
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
NOV
DEC
1
0.0
12.7
5.3
8.9
0.0
10.7
0.0
18.2
10.0
1.2
1.0
0.8
2
39.9
9.4
1.5
6.6
0.0
0.5
0.0
0.0
0.2
2.4
2.0
1.2
3
35.8
17.8
0.0
3.8
0.5
8.9
14.4
6.6
1.1
2.0
1.2
2.8
4
20.8
14.5
0.0
25.9
26.2
62.1
0.2
0.0
12.3
6.2
2.0
36.8
5
58.4
21.3
13.2
2.8
25.7
0.0
18.2
0.0
0.2
0.4
0.0
0.0
6
14.5
5.3
1.0
1.5
6.1
11.4
2.8
0.0
0.0
0.8
0.0
0.0
7
0.0
3.0
42.2
53.8
25.4
0.0
0.0
0.0
0.0
0.6
0.2
70.4
8
30.7
11.7
3.8
19.8
72.4
0.0
0.8
0.0
0.0
0.2
0.0
0.2
9
13.7
28.2
5.3
20.6
78.0
0.0
0.0
0.0
20.3
0.0
0.0
0.2
10
29.0
53.8
10.2
27.9
31.0
0.5
0.0
0.0
0.2
0.0
0.6
0.0
11
24.6
0.0
6.1
0.0
0.0
0.0
0.4
0.0
0.0
0.9
2.2
0.0
12
8.9
96.5
1.1
0.0
3.8
0.0
44.7
0.0
0.0
13.2
0.9
15.8
13
8.4
28.4
0.0
0.0
0.0
0.0
0.4
0.0
66.2
20.4
0.0
0.0
14
88.4
55.9
0.0
0.0
0.0
0.0
12.3
0.0
0.0
1.0
0.0
0.0
15
2.8
1.5
76.7
8.9
16.5
2.5
0.0
0.0
0.0
0.0
0.0
1.0
16
1.5
27.9
10.4
0.0
45.7
2.3
0.0
0.4
0.0
0.0
0.0
0.4
17
1.0
17.3
25.7
0.0
14.0
0.5
0.0
0.7
0.0
0.0
5.0
0.0
18
0.0
75.7
13.2
0.0
6.4
0.3
0.0
0.0
0.0
0.0
0.0
19.0
19
31.8
16.3
31.5
0.0
8.4
0.3
0.7
0.0
0.2
0.0
0.0
12.4
20
0.0
27.9
19.3
78.7
5.3
1.3
0.0
0.0
0.0
0.0
0.0
6.8
21
7.1
8.9
13.7
52.1
2.8
0.0
0.0
0.0
0.0
0.0
0.0
5.2
22
58.7
1.3
16.0
26.9
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.2
23
104.4
0.0
34.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
24
0.0
0.0
3.0
3.8
0.0
0.0
0.2
10.8
12.5
0.0
0.0
0.0
25
0.0
8.1
11.2
5.1
17.0
0.0
0.0
0.0
0.0
0.0
9.8
2.0
26
3.8
26.2
10.2
6.9
16.0
0.0
0.0
0.0
0.0
0.0
3.8
4.4
27
11.4
16.0
0.0
1.3
0.0
485.1
0.8
0.0
0.0
0.0
4.0
8.0
28
16.0
46.7
0.0
2.3
0.0
0.0
0.0
0.0
20.5
0.0
6.4
0.0
29
21.6
6.4
20.6
0.0
0.0
0.8
0.0
0.2
0.0
3.8
0.0
30
23.9
0.8
1.5
0.0
0.0
0.0
0.0
2.5
0.0
91.8
0.0
31
6.60
5.3
0.8
4.7
Total
663.7
632.5
586.3
97.5
41.4
146.4
49.3
134.7
187.6
Mean
21.4
22.6
11.8
12.7
12.9
19.5
3.1
1.3
4.9
1.6
4.5
6.1
Raindays
25
25
25
21
18
13
14
8
13
12
15
18
0.0
367.1 379.7 401.1
0.0
0.0
46
FALELIMA SAVAII
DAILY RAINFALL
Station #: 76019
District;
Location;
0
13 29' 11" SOUTH
Height Above MSL.
0
172 28' 46" WEST.
12m.
SAV76010 (begin date: UNKNOWN)
YEAR
2008
DAY
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
NOV
DEC
1
0.0
0.0
143.6
25.2
0.0
14.2
0.0
0.0
38.8
0.4
2.8
19.6
2
0.0
0.0
128.2
12.4
0.0
24.2
0.0
0.0
4.6
2.4
2.4
9.6
3
14.0
0.0
36.0
0.0
0.0
6.2
0.2
0.0
0.6
0.2
0.0
6.4
4
0.0
0.2
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
10.2
5
0.0
0.0
6.4
15.6
0.2
0.0
0.0
0.0
0.0
0.0
0.0
35.8
6
0.0
0.0
0.0
0.0
0.0
7.1
0.0
0.0
0.0
49.4
24.8
76.2
7
18.2
0.0
0.0
6.8
0.2
96.4
1.6
0.0
0.0
0.0
27.6
57.2
8
74.2
0.0
0.0
4.2
0.2
2.4
47.8
0.0
0.0
0.0
44.4
89.0
9
94.8
5.6
0.0
0.0
0.2
4.6
1.2
0.0
0.0
0.0
9.8
0.0
10
96.4
0.0
101.6
2.8
0.0
2.4
0.8
0.0
0.0
9.6
0.0
0.0
11
15.8
0.0
0.0
2.4
0.0
0.6
20.1
0.0
16.4
0.0
0.0
0.0
12
74.4
53.4
0.0
0.0
0.0
0.2
0.0
0.0
0.0
0.4
21.2
0.0
13
6.4
24.2
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.4
95.0
14
1.8
20.2
6.4
0.0
0.0
0.0
60.8
0.0
0.0
2.4
8.2
0.0
15
0.0
0.0
0.0
0.0
0.0
0.0
6.4
0.0
27.2
0.0
4.4
0.0
16
0.0
48.8
0.0
0.0
0.0
0.0
2.4
8.4
4.6
0.0
13.2
0.0
17
0.8
0.0
0.0
41.4
0.0
0.0
0.0
19.8
6.8
10.0
0.0
0.0
18
6.8
20.4
0.0
0.0
0.0
0.0
0.0
0.0
0.4
0.0
0.0
2.8
19
13.8
2.4
0.0
0.0
0.0
0.0
0.0
0.0
0.2
0.0
8.4
4.6
20
0.0
5.2
0.0
0.0
0.2
0.0
0.0
0.0
0.0
0.0
12.8
29.2
21
149.4
0.0
0.0
3.8
0.0
0.0
0.0
0.0
0.0
0.0
42.2
11.2
22
20.4
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
3.4
0.0
23
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
9.2
0.0
4.2
0.0
24
0.0
0.0
78.2
0.2
0.2
0.0
0.0
2.8
0.0
0.0
0.0
0.0
25
0.0
4.4
2.6
0.0
0.0
0.0
0.0
0.0
70.2
33.8
37.6
0.0
26
177.2
18.4
0.0
0.0
0.0
0.0
0.0
0.0
8.2
0.2
12.8
0.0
27
0.0
5.4
0.0
0.0
0.0
2.2
0.0
0.0
4.4
0.0
33.6
0.0
28
1.2
45.6
0.0
0.0
0.0
4.0
0.0
0.0
0.4
0.0
17.4
0.0
29
0.0
0.0
13.6
0.0
0.0
0.0
0.0
0.0
4.0
0.2
0.0
0.0
0.0
0.0
0.0
0.0
101.8
2.4
0.0
0.0
0.0
0.0
0.0
0.4
331.6
446.8
30
0.0
10.6
0.0
31
0.00
2.4
0.0
Total
765.6
254.2
529.6
114.8
1.2
164.5
141.3
31.0
Mean
24.7
8.8
17.1
3.7
0.0
5.5
4.6
1.0
9.6
3.6
11.1
14.4
Raindays
16
13
11
10
6
12
9
3
16
13
20
13
297.8 111.8
0.0
47