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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 ______________________
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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.
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Table of Contents Preface iii Table of Contents iv List of Figures v List of Tables v Acknowledgements vi Abstract vii 1.0 Introduction 1 2.0 Background Information for Samoa and Falelima 4
2.1 Geography and Environment 4 2.2 National History 5 2.3 People and Culture 7 2.4 Water and Sanitation 8 2.5 Falelima, Savai’I 9 2.6 GEF UNDP Grant Project 12
3.0 Methods and Data 18 3.1 Precipitation 18 3.2 Collection Area 21 3.3 Water Storage 22 3.4 Water Demand 23 3.5 Rainwater Harvesting Model 25
4.0 Results and Discussion 31 4.1 Design Curve 31 4.2 Meeting Basic Access Requirements 34 4.3 Using Variable Demand Levels 38
5.0 Conclusions and Recommendations 38 References 41 Appendix A:Village Data 42 B: Rainfall Data 45
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List of Figures
Figure 1: Map of Oceania 5 Figure 2: Map of Samoa 10 Figure 3: Tank reinforcement on formwork 16 Figure 4: Appling second ferrocement layer 16 Figure 5: Completed tank 17 Figure 6: Modeled daily water storage at Family 40 household 30 Figure 7: Modeled daily water storage at Family 40 household with rationing 31 Figure 8: 50 l/c/d curves for years 2006 – 2008 32 Figure 9: Design Curves for Falelima Samoa (100% reliability) 33 Figure 10: Demand curves for various reliability rates. 34 Figure 11: Families initial per capita ability for water supply 35 Figure 12: Families water supply capacity at the completion of tank construction 36
List of Tables
Table 1: Tank Materials and Costs 14 Table 2: Recorded Annual Rainfall in Falelima, Samoa 20 Table 3: WHO Water Service level definitions 24 Table 4: Model Parameters 26 Table 5: Model Results 28 Table 6: Model Parameters for Household 40 28 Table 7: Initial model calculations for Family 40 household 29 Table 8: Families in each range of daily water supply before and after
the water project 29 Table 9: Families in each range of daily water supply before and after
the water project 36 Table 10: Families not exceeding basic water access of 20 l/c/d 37 Table 11: List of possible solutions for families to exceed 20 l/c/d
and their estimated costs. 38
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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.
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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.
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
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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
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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
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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
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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.
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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
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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).
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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
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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.
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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
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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.
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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).
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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 ($538
USD). The materials and costs for a tank are shown in Table 1. The families also
receive one 5m section of gutter and a downspout with each tank to increase the
collection area being used.
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Table 1: Tank Materials and Costs
Material Quantity Unit Cost WS$
Per Tank Cost WS$
Per Tank Cost US$
Chicken Wire 6'x150' 1 $196.00 $196.00 $75.38Pig fence 3' x 50meter 1 $185.00 $185.00 $71.15Plain Wire #8 1 $155.00 $155.00 $59.62HardBoard 3/16" 0.25 $29.50 $7.38 $2.84Galv Nails 2" Lbs 1.5 $3.50 $5.25 $2.02Galv Nails 3" Lbs 1.5 $3.50 $5.25 $2.02Cement sacks 40 kg 23 $23.50 $540.50 $207.88Tank Tap 1/2" 1 $20.00 $20.00 $7.69Faucet Socket 1/2" 1 $1.50 $1.50 $0.58Gate Valve 3/4" 1 $20.00 $20.00 $7.69Valve Socket 3/4" 1 $2.00 $2.00 $0.77PVC Pipe 1/2"x10' 1 $9.00 $9.00 $3.46PVC Pipe 3/4"x10' 0.5 $15.00 $7.50 $2.88PVC Glue 236 ml 0.5 $12.00 $6.00 $2.31Seal Tape 1 $2.00 $2.00 $0.77Paint Brush 4" 2 $22.50 $45.00 $17.31Plastic Spouting 5 meter 1 $62.00 $62.00 $23.85Rainhead Outlet 1 $36.00 $36.00 $13.85Down Pipe 3meter 1 $38.00 $38.00 $14.62Spouting Bend 3" 1 $8.00 $8.00 $3.08Stop Ends (L & R) 2 $5.00 $10.00 $3.85External Brackets 6 $4.50 $27.00 $10.38Joiner 1 $13.00 $13.00 $5.00Total Cost $1,401.38 $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.
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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
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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
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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.
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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.
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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.
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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 Rainfall (mm)
2006* 4357 2007 3687 2008 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.
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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.
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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.
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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 Units Value(s)Tank Volume l Varied Initial Tank Level l 0 Roof Area m2 Varied Family Size # Varied
Water Demand l/cap/d 20, 50, 70
Runoff Coefficient # 0.85
Gutter Factor # 0 - 1 Rationing Level l 0 - 1 Rationing Factor # 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 unit Length of record years Satisfaction % Reliability % Longest dry spell 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 l 38600 Initial Tank Level l 0 Roof Area m2 187 Number of People # 11 Water Demand l/cap/d 50 Runoff Coefficient # 0.85 Gutter Factor # 0.508 Rationing Level l na Rationing Factor # na
28
Table 7: Initial model calculations for Family 40 household
Dat
e
Rai
n (m
m)
Run
off (
l)
Stor
age+
Run
off (
l)O
verf
low
(l) St
orag
e A
fter
Ove
rflo
w
(l) Dem
and
(l)
Stor
age
- D
eman
d (l)
Supp
ly (l
)
Dem
and
Met
Run
of D
ry
Day
s
1/26/06 64.8 5230 5230 0 5230 550 4680 550 1 01/27/06 28.7 2318 6998 0 6998 550 6448 550 1 01/28/06 33.5 2707 9155 0 9155 550 8605 550 1 01/29/06 31.8 2564 11169 0 11169 550 10619 550 1 01/30/06 62.7 5066 15684 0 15684 550 15134 550 1 01/31/06 114.8 9270 24405 0 24405 550 23855 550 1 02/1/06 167.6 13536 37391 0 37391 550 36841 550 1 02/2/06 137.2 11075 47916 9316 38600 550 38050 550 1 02/3/06 48.5 3917 41967 3367 38600 550 38050 550 1 0 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 2.93 yr
Satisfaction 93.18% Reliability 92.06%
Longest dry spell 32 days
29
0
5,000
10,000
15,000
20,000
25,000
30,000
35,000
40,000
Jan-
06Fe
b-06
Mar
-06
Apr-
06M
ay-0
6Ju
n-06
Jul-0
6Au
g-06
Sep-
06O
ct-0
6N
ov-0
6D
ec-0
6Ja
n-07
Feb-
07M
ar-0
7Ap
r-07
May
-07
Jun-
07Ju
l-07
Aug-
07Se
p-07
Oct
-07
Nov
-07
Dec
-07
Jan-
08Fe
b-08
Mar
-08
Apr-
08M
ay-0
8Ju
n-08
Jul-0
8Au
g-08
Sep-
08O
ct-0
8N
ov-0
8D
ec-0
8
Date
Tank
Vol
ume
(litre
s)
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
0
5,000
10,000
15,000
20,000
25,000
30,000
35,000
40,000
Jan-
06Fe
b-06
Mar
-06
Apr-
06M
ay-0
6Ju
n-06
Jul-0
6Au
g-06
Sep-
06O
ct-0
6N
ov-0
6D
ec-0
6Ja
n-07
Feb-
07M
ar-0
7Ap
r-07
May
-07
Jun-
07Ju
l-07
Aug-
07Se
p-07
Oct
-07
Nov
-07
Dec
-07
Jan-
08Fe
b-08
Mar
-08
Apr-
08M
ay-0
8Ju
n-08
Jul-0
8Au
g-08
Sep-
08O
ct-0
8N
ov-0
8D
ec-0
8
Date
Tank
Vol
ume
(litre
s)
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.
0
5
10
15
20
25
30
35
40
0 1000 2000 3000 4000 5000 6000 7000
Tank Volume L
Col
lect
ion
Are
a m
2
200620072008
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.
0
5
10
15
20
25
30
35
40
0 1000 2000 3000 4000 5000 6000 7000 8000Tank Volume L
Col
lect
ion
Are
a m
2
20 L/c/d50 L/c/d70 L/c/d
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
0
5
10
15
20
25
30
35
40
45
50
0 1000 2000 3000 4000 5000 6000 7000 8000
Tank Volume (l)
Col
lect
ion
Are
a (m
2 )
70 l/c/d 100%70 l/c/d 99%70 l/c/d 95%70 l/c/d 90%50 l/c/d 100%50 l/c/d 99%50 l/c/d 95%50 l/c/d 90%20 l/c/d 100%
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
0
5
10
15
20
25
30
35
40
0 1000 2000 3000 4000 5000 6000 7000 8000
Tank Volume L
Colle
ctio
n Ar
ea m
2
20 L/c/d50 L/c/d70 L/c/dFamilies Initial
Figure 11: Families initial per capita ability for water supply
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
0
5
10
15
20
25
30
35
40
45
50
0 2000 4000 6000 8000 10000 12000 14000 16000Tank Volume L
Colle
ctio
n A
rea
m2
20 L/c/d50 L/c/d70 L/c/dFamilies After Project
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
# Families Before Project
# Families After
Project
<20 l/c/d 18 6
20 l/c/d - 50 l/c/d
29 35
50 l/c/d - 70 l/c/d
9 11
>70 l/c/d 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
Household Members Total Storage l
Area Available
m2
Area Collected
m2
Area Need for 20 l/c/d
m2 Notes
2 16 13,000 71 17 317 Started without
Collection
3 9 13,000 107 30 52 Started without
Collection 5 19 30,100 43 32 96
6 10 22,900 11 11 31 Full
collection area in use
20 10 18,400 55 15 40 Did not
Participate in Project
30 6 13,900 33 15 19 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
5 Complete guttering and
construct 50 m2 of guttered area
WS$1,250 USD$480
6 Construct 16 m2 of additional guttered collection area
WS$550 USD$212
20 Add gutter to existing roof WS$340 USD$130
30 Add gutter to existing roof 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
Appendix A: Village Data
Hou
seho
ld ID
Family Size
Initial Storage
(m3 )
Initial Storage
per Cap
ita
(m3 /c)
Total R
oof A
rea (m
2 )
Initial A
rea Co
llected
(m2 )
% Area Co
llected
Initial A
rea Co
llected
per
Capita (m
2 /cap)
Fina
l Total Storage
(m3 )
Fina
l Storage
per Cap
ita
(l/c)
Fina
l Area Co
llected
(m2 )
Fina
l Area Co
llected
per
Capita (m
2 /cap)
1 4 0.0 0.0 55 0 0% 0.0 13.0 3250 17 4.3 2 16 0.0 0.0 71 0 0% 0.0 13.0 813 17 1.1 3 9 0.0 0.0 107 0 0% 0.0 13.0 1444 30 3.3 4 8 3.4 0.4 27 6 22% 14.2 16.4 2048 28 3.5 5 19 17.1 0.9 43 22 51% 24.5 30.1 1582 32 1.7 6 10 9.9 1.0 11 11 100% 11.1 22.9 2289 11 1.1 7 6 6.8 1.1 185 37 20% 32.9 19.8 3292 54 9.0 8 6 6.8 1.1 124 44 35% 39.1 19.8 3292 69 11.5 9 14 18.8 1.3 55 33 60% 24.6 31.8 2269 43 3.1
10 12 16.1 1.3 103 37 36% 27.6 29.1 2424 52 4.3 11 8 11.3 1.4 164 19 12% 13.4 24.3 3043 48 6.0 12 16 23.7 1.5 82 31 38% 21.0 36.7 2292 52 3.3 13 9 14.8 1.6 110 29 26% 17.6 27.8 3093 47 5.2 14 2 3.4 1.7 82 14 17% 8.3 16.4 8190 39 19.5 15 2 3.4 1.7 89 50 56% 29.6 16.4 8190 85 42.5 16 11 19.5 1.8 124 45 36% 25.4 32.5 2954 65 5.9 17 12 21.3 1.8 155 95 61% 53.6 34.3 2856 115 9.6 18 9 16.3 1.8 33 28 85% 15.4 29.3 3258 33 3.7 19 11 20.0 1.8 137 49 36% 27.0 33.0 2997 74 6.7 20 10 18.4 1.8 55 15 27% 8.1 18.4 1842 15 1.5 21 14 26.0 1.9 96 63 66% 33.9 26.0 1856 63 4.5 22 10 18.8 1.9 93 43 46% 22.9 31.8 3180 68 6.8 23 11 20.7 1.9 196 62 32% 32.9 33.7 3065 97 8.8 24 8 15.4 1.9 57 31 54% 16.1 15.4 1924 31 3.9 25 16 32.5 2.0 144 69 48% 33.9 45.5 2846 89 5.6 26 18 37.6 2.1 144 34 24% 16.3 50.6 2809 59 3.3
42
Hou
seho
ld ID
Family Size
Initial Storage
(m3 )
Initial Storage
per Cap
ita
(m3 /c)
Total R
oof A
rea (m
2 )
Initial A
rea Co
llected
(m2 )
% Area Co
llected
Initial A
rea Co
llected
per
Capita (m
2 /cap)
Fina
l Total Storage
(m3 )
Fina
l Storage
per Cap
ita
(l/c)
Fina
l Area Co
llected
(m2 )
Fina
l Area Co
llected
per
Capita (m
2 /cap)
27 7 14.7 2.1 103 55 53% 26.2 14.7 2097 55 7.9 28 9 19.6 2.2 88 35 40% 16.1 19.6 2179 35 3.9 29 8 18.3 2.3 79 40 51% 17.5 18.3 2284 40 5.0 30 6 13.9 2.3 33 15 45% 6.5 13.9 2323 15 2.5 31 9 22.1 2.5 106 61 58% 24.9 22.1 2454 61 6.8 32 9 22.1 2.5 217 61 28% 24.8 35.1 3904 76 8.4 33 9 22.5 2.5 55 25 45% 10.0 22.5 2498 25 2.8 34 5 12.6 2.5 164 60 37% 23.8 25.6 5118 75 15.0 35 8 20.4 2.5 50 38 76% 14.9 20.4 2545 38 4.8 36 11 28.3 2.6 187 72 39% 28.0 28.3 2570 72 6.5 37 11 28.6 2.6 66 46 70% 17.7 28.6 2602 46 4.2 38 7 21.3 3.0 128 80 63% 26.3 21.3 3039 80 11.4 39 9 27.7 3.1 110 38 35% 12.3 40.7 4522 59 6.6 40 11 38.6 3.5 187 95 51% 27.1 38.6 3505 95 8.6 41 10 36.0 3.6 293 90 31% 25.0 49.0 4897 110 11.0 42 10 36.7 3.7 164 53 32% 14.4 36.7 3671 53 5.3 43 10 38.8 3.9 308 98 32% 25.3 38.8 3876 98 9.8 44 5 20.0 4.0 162 27 17% 6.8 33.0 6590 57 11.4 45 10 40.5 4.1 202 48 24% 11.8 53.5 5354 65 6.5 46 8 32.6 4.1 151 110 73% 27.0 32.6 4069 110 13.8 47 4 17.0 4.3 115 45 39% 10.6 17.0 4260 45 11.3 48 8 34.6 4.3 220 63 29% 14.6 34.6 4328 63 7.9 49 8 35.4 4.4 738 227 31% 51.3 48.4 6054 262 32.8 50 7 32.8 4.7 202 19 9% 4.1 32.8 4687 19 2.7 51 7 34.2 4.9 187 54 29% 11.1 47.2 6741 84 12.0 52 3 16.2 5.4 133 36 27% 6.7 16.2 5413 36 12.0 53 6 33.4 5.6 250 60 24% 10.8 33.4 5565 60 10.0 54 3 17.2 5.7 196 60 31% 10.4 17.2 5747 60 20.0 55 5 28.9 5.8 82 60 73% 10.4 28.9 5772 60 12.0 56 6 35.4 5.9 165 67 41% 11.3 48.4 8072 92 15.3
43
Hou
seho
ld ID
Family Size
Initial Storage
(m3 )
Initial Storage
per Cap
ita
(m3 /c)
Total R
oof A
rea (m
2 )
Initial A
rea Co
llected
(m2 )
% Area Co
llected
Initial A
rea Co
llected
per
Capita (m
2 /cap)
Fina
l Total Storage
(m3 )
Fina
l Storage
per Cap
ita
(l/c)
Fina
l Area Co
llected
(m2 )
Fina
l Area Co
llected
per
Capita (m
2 /cap)
57 8 49.5 6.2 226 80 35% 12.9 49.5 6189 80 10.0 58 5 31.3 6.3 210 85 40% 13.6 31.3 6256 85 17.0 59 6 41.5 6.9 260 230 88% 33.2 41.5 6920 230 38.3 60 9 62.6 7.0 250 92 37% 13.2 62.6 6958 92 10.2 61 8 64.3 8.0 293 112 38% 13.9 64.3 8033 112 14.0 62 4 34.7 8.7 155 62 40% 7.2 47.7 11915 82 20.5 63 5 59.9 12.0 568 170 30% 14.2 72.9 14578 190 38.0
Ave 8.7 24 3.2 153 56 40% 18.8 31.2 4201 67 9.8 Min 19 64 12.0 738 230 100% 53.6 72.9 14578 262 42.5 Max 2 0 0 11 0 0% 0 13.0 812.5 11 1.1
44
Appendix B: Falelima, Samoa Rainfall Data (measurements in mm) Station #: 76019
District;
Location; 130 29' 11" SOUTH 1720 28' 46" WEST.Height Above MSL. 12m.
YEAR 2006DAY JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
1 167.6 7.6 0.0 1.0 0.0 0.0 0.0 27.9 0.0 4.3 47.52 137.2 4.1 0.0 0.5 0.0 0.0 0.0 0.0 26.7 0.0 16.53 48.5 13.2 2.5 1.3 0.0 0.0 0.0 0.3 0.0 0.0 8.94 46.2 0.0 3.8 0.3 0.5 0.0 0.0 0.0 15.2 0.0 49.35 101.6 0.0 0.0 0.0 0.5 0.0 0.0 3.8 6.4 0.0 31.8
6 115.3 106.7 10.7 0.0 0.0 0.0 0.5 7.1 12.4 0.0 0.07 44.5 0.0 8.9 1.3 0.3 0.0 0.0 0.0 0.0 6.4 0.08 124.7 1.5 41.1 0.8 0.0 0.0 0.0 0.0 0.0 0.0 0.09 125.7 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 33.812 89.4 25.9 0.3 3.8 9.1 0.3 3.8 7.6 0.3 9.4 34.813 47.5 55.9 3.8 7.9 0.0 0.3 6.4 0.0 1.0 14.7 7.614 0.5 5.1 11.7 16.5 3.8 2.8 0.0 0.0 0.5 11.7 3.015 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 3.317 37.1 0.0 0.0 39.4 0.3 21.1 0.5 0.0 0.0 54.9 11.418 53.8 0.0 0.0 5.6 0.0 16.0 2.5 0.0 0.0 33.0 10.219 16.0 22.6 0.0 3.8 0.0 3.8 0.0 0.0 0.0 26.7 18.320 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 31.222 42.7 96.5 3.6 2.5 0.0 0.0 0.0 3.8 0.0 3.8 0.023 17.0 1.3 0.8 0.0 17.8 0.0 0.0 11.9 0.0 3.0 0.024 0.0 0.0 1.3 36.8 17.3 0.0 0.0 0.0 103.9 1.5 87.925 4.1 0.8 3.3 0.5 2.5 13.2 0.0 0.3 1.0 4.3 0.0
26 64.8 0.0 16.5 16.5 0.0 0.0 30.5 0.0 0.0 0.0 6.1 9.127 28.7 0.3 44.2 1.3 0.0 0.0 6.9 0.0 8.9 0.0 0.0 0.028 33.5 14.2 0.0 3.0 0.0 0.0 0.0 0.0 14.0 0.0 0.0 3.329 31.8 0.0 0.9 1.0 0.0 0.0 0.0 0.5 10.2 0.0 73.2 0.030 62.7 0.0 36.8 5.3 0.0 0.0 0.0 18.3 0.0 0.0 0.0 30.531 114.81 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 47.8 163.8 230.9 391.7 544.8Mean 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
FALELIMA SAVAII DAILY RAINFALL
SAV76010 (begin date: UNKNOWN)
45
Station #: 76019
District;
Location; 130 29' 11" SOUTH 1720 28' 46" WEST.Height Above MSL. 12m.
YEAR 2007
DAY JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC1 0.0 12.7 5.3 8.9 0.0 10.7 0.0 18.2 10.0 1.2 1.0 0.82 39.9 9.4 1.5 6.6 0.0 0.5 0.0 0.0 0.2 2.4 2.0 1.23 35.8 17.8 0.0 3.8 0.5 8.9 14.4 6.6 1.1 2.0 1.2 2.84 20.8 14.5 0.0 25.9 26.2 62.1 0.2 0.0 12.3 6.2 2.0 36.85 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 0.07 0.0 3.0 42.2 53.8 25.4 0.0 0.0 0.0 0.0 0.6 0.2 70.48 30.7 11.7 3.8 19.8 72.4 0.0 0.8 0.0 0.0 0.2 0.0 0.29 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 0.012 8.9 96.5 1.1 0.0 3.8 0.0 44.7 0.0 0.0 13.2 0.9 15.813 8.4 28.4 0.0 0.0 0.0 0.0 0.4 0.0 66.2 20.4 0.0 0.014 88.4 55.9 0.0 0.0 0.0 0.0 12.3 0.0 0.0 1.0 0.0 0.015 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 0.417 1.0 17.3 25.7 0.0 14.0 0.5 0.0 0.7 0.0 0.0 5.0 0.018 0.0 75.7 13.2 0.0 6.4 0.3 0.0 0.0 0.0 0.0 0.0 19.019 31.8 16.3 31.5 0.0 8.4 0.3 0.7 0.0 0.2 0.0 0.0 12.420 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 5.222 58.7 1.3 16.0 26.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.223 104.4 0.0 34.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.024 0.0 0.0 3.0 3.8 0.0 0.0 0.2 10.8 12.5 0.0 0.0 0.025 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 4.427 11.4 16.0 0.0 1.3 0.0 485.1 0.8 0.0 0.0 0.0 4.0 8.028 16.0 46.7 0.0 2.3 0.0 0.0 0.0 0.0 20.5 0.0 6.4 0.029 21.6 6.4 20.6 0.0 0.0 0.8 0.0 0.2 0.0 3.8 0.030 23.9 0.8 1.5 0.0 0.0 0.0 0.0 2.5 0.0 91.8 0.031 6.60 5.3 0.0 0.8 4.7 0.0 0.0
Total 663.7 632.5 367.1 379.7 401.1 586.3 97.5 41.4 146.4 49.3 134.7 187.6Mean 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
FALELIMA SAVAII DAILY RAINFALL
SAV76010 (begin date: UNKNOWN)
46
Station #: 76019District;
Location; 130 29' 11" SOUTH 1720 28' 46" WEST.Height Above MSL. 12m.
YEAR 2008
DAY JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC1 0.0 0.0 143.6 25.2 0.0 14.2 0.0 0.0 38.8 0.4 2.8 19.62 0.0 0.0 128.2 12.4 0.0 24.2 0.0 0.0 4.6 2.4 2.4 9.63 14.0 0.0 36.0 0.0 0.0 6.2 0.2 0.0 0.6 0.2 0.0 6.44 0.0 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 10.25 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 76.27 18.2 0.0 0.0 6.8 0.2 96.4 1.6 0.0 0.0 0.0 27.6 57.28 74.2 0.0 0.0 4.2 0.2 2.4 47.8 0.0 0.0 0.0 44.4 89.09 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 0.012 74.4 53.4 0.0 0.0 0.0 0.2 0.0 0.0 0.0 0.4 21.2 0.013 6.4 24.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.4 95.014 1.8 20.2 6.4 0.0 0.0 0.0 60.8 0.0 0.0 2.4 8.2 0.015 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 0.017 0.8 0.0 0.0 41.4 0.0 0.0 0.0 19.8 6.8 10.0 0.0 0.018 6.8 20.4 0.0 0.0 0.0 0.0 0.0 0.0 0.4 0.0 0.0 2.819 13.8 2.4 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.0 8.4 4.620 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 11.222 20.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3.4 0.023 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 9.2 0.0 4.2 0.024 0.0 0.0 78.2 0.2 0.2 0.0 0.0 2.8 0.0 0.0 0.0 0.025 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 0.027 0.0 5.4 0.0 0.0 0.0 2.2 0.0 0.0 4.4 0.0 33.6 0.028 1.2 45.6 0.0 0.0 0.0 4.0 0.0 0.0 0.4 0.0 17.4 0.029 0.0 0.0 13.6 0.0 0.0 0.0 0.0 0.0 4.0 0.2 0.0 0.030 0.0 10.6 0.0 0.0 0.0 0.0 0.0 101.8 2.4 0.0 0.031 0.00 2.4 0.0 0.0 0.0 0.0 0.4 0.0
Total 765.6 254.2 529.6 114.8 1.2 164.5 141.3 31.0 297.8 111.8 331.6 446.8Mean 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
FALELIMA SAVAII DAILY RAINFALL
SAV76010 (begin date: UNKNOWN)
47
