An Analysis of Household Rainwater Harvesting Systems in Falelima, Samoa

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 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 iv 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 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.

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