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SITE SUITABILITY ANALYSIS FOR WATER HARVESTING STRUCTURES IN SURIYAWEWA, HAMBANTOTA DISTRICT USING GIS TECHNIQUES

SITE SUITABILITY ANALYSIS FOR WATER HARVESTING STRUCTURES IN SURIYAWEWA, HAMBANTOTA DISTRICT USING GIS TECHNIQUES Indishe Prabath Senanayake (07/8015) Degree of Master of Philosophy Department of Earth
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SITE SUITABILITY ANALYSIS FOR WATER HARVESTING STRUCTURES IN SURIYAWEWA, HAMBANTOTA DISTRICT USING GIS TECHNIQUES Indishe Prabath Senanayake (07/8015) Degree of Master of Philosophy Department of Earth Resources Engineering University of Moratuwa Sri Lanka February 2012 SITE SUITABILITY ANALYSIS FOR WATER HARVESTING STRUCTURES IN SURIYAWEWA, HAMBANTOTA DISTRICT USING GIS TECHNIQUES Indishe Prabath Senanayake (07/8015) Thesis submitted in partial fulfillment of the requirements for the Degree Master of Philosophy. Department of Earth Resources Engineering University of Moratuwa Sri Lanka February 2012 DECLARATION I declare that this is my own work and this thesis does not incorporate without acknowledgement any material previously submitted for a Degree or Diploma in any other University or institute of higher learning and to the best of my knowledge and belief it does not contain any material previously published or written by another person except where the acknowledgement is made in the text. Also, I hereby grant to University of Moratuwa the non-exclusive right to reproduce and distribute my thesis, in whole or in part in print, electronic or other medium. I retain the right to use this content in whole or part in future works (such as articles or books). Signature: Date: The above candidate has carried out research for the MPhil thesis under my supervision. Signature of Supervisor I: Date: Signature of Supervisor II: Date: i ABSTRACT Sri Lanka receives an average annual rainfall varying from 900mm to 6000mm. However, the rainfall is not distributed equally over the island. Hence, traditionally, the country is divided into three main climatic zones as wet zone, dry zone and intermediate zone. Two thirds of the island is occupied by the dry zone, which receives less than 1750mm of average annual rainfall. The dry zone periodically has faced water stress conditions from the past, and Hambantota District appears to be a severely affected area, on the basis of surface water availability. With the ongoing development projects, the demand for water in the district will increase in the next few years. Therefore, implementation of a proper water management system as well as preservation of existing surface and groundwater resources is essential to overcome this problem. A methodology is developed to find the most suitable locations for water harvesting structures in Hambantota District by using Geographic Information System (GIS) techniques. Suriyawewa Divisional Secretariat area is selected as the research area considering its average climatic conditions and location within Hambantota District. This methodology can be generalized to the whole District in the first instance. The research area is hydrologically analyzed to discretize the area into catchments and the preferred catchments to harvest the runoff based on surface area, slope and rainfall are found by using GIS techniques. The selected catchments are then analyzed with geological data and drainage characteristics to find the most suitable catchments to construct reservoirs to store rainwater. The analysis yields four such locations, which were subsequently field verified for spatial accuracy. However detailed local investigations are necessary before proceeding to actual construction of the reservoirs. Groundwater recharging also plays an important role in water management, as groundwater represents 30.1% of the world s fresh water resources. GIS techniques are employed to integrate data on land use, climate, soil, stream pattern and ground slopes, and consequently to find potential areas for groundwater recharging. Here also, detailed local investigation must precede any construction work in the selected areas. Also, potential areas to implement roof water harvesting projects in Suriyawewa are found by analyzing the rainfall and building cover by using GIS techniques. These areas are recommended to be used as project areas when implementing efficient roof water harvesting methods. The methodology adopted here for Hambantota District can be used for water management in other Districts of the Dry Zone of Sri Lanka such as Monaragala, Puttalam, Ampara, Badulla and Kurunegala, as a solution for water stress conditions in those areas. An increment in water harvesting can significantly increase the crop yields in these areas and improve the economy as most of the Districts in the Dry Zone are agriculture-based. Also, a proper water management system is a must for the industrial development of the area under focus, while it gives a solution to the problems regarding drinking water. Proper water supply plays a major role in infrastructure development of these areas and would form the foundation for the overall development of the country. ii ACKNOWLEDGEMENTS Foremost, I would like to express my sincere gratitude to my supervisors, Prof. U.G.A. Puswewala, Professor at Department of Civil Engineering and Dean of the Faculty of Engineering, University of Moratuwa, and Dr. D.M.D.O.K. Dissanayake, Senior Lecturer at the Department of Earth Resources Engineering, University of Moratuwa and Chairman of the Renewable Energy Authority. Without their immense guidance and persistent help this dissertation would not have been possible. The research presented in this thesis was carried out at the Department of Earth Resources Engineering, University of Moratuwa under the financial assistance from the University Research Fund. I would like to thank the University of Moratuwa, and the Senate Research Committee for the financial assistance extended. Beside my supervisors, I would like to thank the chairman of the progress review committee, Prof. S.A.S. Kulatilake, for his encouragement and insightful comments. I would also like to thank Prof. R.A. Attalage, Director of the Postgraduate Studies Division, University of Moratuwa and his staff for their support. My sincere thanks also go to Dr. (Mrs.) S.C.S. Karunaratne, Head of the Department of Earth Resources Engineering and Dr. A.M.K.B. Abeysinghe, Research Coordinator at the Department of Earth Resources Engineering, University of Moratuwa, for their kind support. I owe my deepest gratitude to Mrs. W.L. Gunawardena, Lecturer at the Department of Town and Country Planning, University of Moratuwa for her kind assistance on Remote Sensing and GIS software during this research. It is with immense gratitude that I acknowledge the support of late Surveyor General Mr. B.J.P. Mendis, Additional Surveyor General Mr. K. Thawalingam and the staff of the Survey Department of Sri Lanka for providing me the digital data of Suriyawewa at a concession. I am indebted to the staff of Meteorological Department of Sri Lanka, Geological Survey and Mines Bureau and the Irrigation Department of Ambalantota for providing me with the required climatic, geological and irrigation data respectively for this research. I am grateful to the academic and non-academic staff of the Department of Earth Resources Engineering, and the Department of Civil Engineering, University of Moratuwa for their guidance and support. Also, I wish to thank library staff and the staff of Examination Division of University of Moratuwa for their help during the work. My gratitude goes to all the authors and publishers of the literature I used, in this work. iii In the field, residents of the study area helped and gave me essential details. I highly acknowledge their support with immense gratitude. I express my heartfelt gratitude to my parents, family and friends whose moral and emotional support helped me immensely. Last but not the least, I would like to acknowledge and extend my heartfelt gratitude all of those who supported me in any respect during the completion of this research. I. P. Senanayake B.Sc. Eng (Hons) Department of Civil Engineering University of Moratuwa, Sri Lanka. November 01, 2011 iv TABLE OF CONTENTS Declaration Abstract Acknowledgements Table of contents List of Figures List of tables i ii iii v viii xi 1.0 Introduction Geography and Climate of Sri Lanka Rainfall and the Climatic Zones of Sri Lanka Water Supply and Scarcity in Sri Lanka Water Stress Conditions in Hambantota District Objectives and the Scope of the Project Literature Review Harvesting of Rainwater Rainwater Harvesting (RWH) Technologies Factors Affecting Rainwater Harvesting Project Area: Hambantota District Methodology Introduction Preparation of Digital Maps of Hambantota District Geo-referencing the Scanned Topographical Maps of 19 Hambantota District Digitizing the topographical maps of Hambantota District Generating Digital layers of Hambantota Land Use Preparation of the Digital Elevation Model (DEM) of Hambantota 21 District Terrain Surface model Digital Elevation Model (DEM) Triangulated Irregular Network (TIN) Raster Surfaces Preparation of the Contour Map of Hamantota District Preparation of the Triangulated Irregular Network (TIN) of 23 Hambantota District Preparation of the Raster DEM/ GRID of Hambantota District Generation of the 3D View of Hambantota Terrain Generation of the Slope Map of Hambantota Terrain Generation of the Aspect of Slope Map Field Verification of Data Analysis of Climatic Data Rainfall Temperature 42 v 3.6 Selecting Suriyawewa Divisional Secretariat Area as the Research 43 Area 3.7 Location of Suriyawewa Divisional Secretariat Area Preparation of the Land Use Maps of Suriyawewa Preparation of the Triangulated Irregular Network of Suriyawewa Preparation of the Raster DEM/ GRID of Suriyawewa Generation of the 3D View of Suriyawewa Terrain Satellite Image of Suriyawewa ArcHydro Terrain Preprocessing DEM Reconditioning Fill Sinks Flow Direction Flow Accumulation Stream Definition Stream Segmentation Catchment Grid Delineation Catchment Polygon Processing Drainage Line Processing Drainage Point Processing Analysing the Slope Map of Suriyawewa Slope Map of Suriyawewa Reclassifying the Slope Map Converting Reclassified Slope Map into a Vector Layer Splitting the Slope Map into Catchments Average Annual Rainfall Map of Suriyawewa Selecting the Catchments to harvest rainwater on the basis of 78 Slope and Surface Area Analysis of the Catchments with the rainfall data Analysis of the Selected Catchments Catchment cm Catchment cf Catchment bc Catchment ce Catchment cy Catchment bd Catchment ej Catchment au Catchment bg Catchment dm Catchment cz Catchment el Catchment bp Catchment bh Catchment bj Special case at location D Selection of the locations to construct tanks 103 vi Geological Analysis of the locations Field verification of the selected locations Introducing a methodology to improve the groundwater potential Site suitability analysis for groundwater recharge in 111 Suriyawewa 3.18 Site suitability analysis for Rooftop Water Harvesting in Suriyawewa Proposals to improve the water management in the project area Conclusion References 128 vii LIST OF FIGURES Figure 1.1 Climatic Zones of Sri Lanka (Source: Department of 2 Agriculture) Figure 2.1 Examples of types of guttering 8 Figure 2.2 Roof top water harvesting storage tank in Hambantota 8 Figure 2.3 Western Australia rainwater harvesting system for animal 10 consumption. The runoff-surface is compacted and treated. Figure 2.4 Various forms of flat-land and inter-row water harvesting; 10 from A C increasing Catchment to Cropping Ratio (CCR)/ aridity of location. Figure 2.5 Rainwater harvesting categories 11 Figure 2.6 Elements of Rainwater Harvesting System 12 Figure 2.7 Drainage Patterns 13 Figure 2.8 Location of the Hambantota District in Sri Lanka 15 Figure 3.1 Land Use Map of Hambantota District 21 Figure 3.2 Contour Map of Hambantota District 24 Figure 3.3 Triangulated Irregular Network (TIN) of Hambantota District 25 Figure 3.4 Grid/ Raster DEM of Hambantota District 26 Figure 3.5 3D Scene of the Hambantota District Terrain 27 Figure 3.6 Slope Map of Hambantota District (in degrees) 29 Figure 3.7 The eight slope directions 30 Figure 3.8 Aspect of Slope Map - Hambantota District 31 Figure 3.9 Map showing the Field Visit Locations 33 Figure 3.10 Andara Wewa at Location Figure 3.11 Paddy Fields at Location Figure 3.12 Gonnoruwa Wewa at Location 9 35 Figure 3.13 Distribution of Mean Annual Rainfall of Sri Lanka (in mm) 36 Figure 3.14 Rainfall Stations of Hambantota District 38 Figure 3.15 Average Monthly Rainfall Statistics of Hambantota District 39 Figure 3.16 Average Annual Rainfall Statistics of Hambantota District 40 ( ) Figure 3.17 Average monthly rainfall of Hambantota District 41 Figure 3.18 Average annual rainfall of Hambantota District 41 Figure 3.19 Average Monthly Temperature Statistics of Hambantota 42 District Figure 3.20 Average Annual Temperature Statistics of Hambantota District 42 Figure 3.21 Location of Suriyawewa DS Area in Hambantota District 44 Figure 3.22 Spot Heights Map of Suriyawewa Divisional Secretariat Area 45 Figure 3.23 ArcGIS Model used to generate the Suriyawewa Spot Heights 46 Layer. Figure 3.24 Grama Niladari Divisions of Suriyawewa 47 Figure 3.25 Land Use Map of Suriyawewa 48 Figure 3.26 Tributaries of Suriyawewa 49 Figure 3.27 Contour Map of Suriyawewa 50 Figure 3.28 Triangulated Irregular Network (TIN) of Suriyawewa 52 Figure 3.29 Raster DEM (GRID) of Suriyawewa 53 Figure D Scene of Suriyawewa Terrain 54 Figure 3.31 IIRS Raw Image and Geo-referenced Image 54 Figure 3.32 IIRS Satellite Image of Suriyawewa 55 viii Figure 3.33 Change of the Cross Section Profile of a given location after 56 the raw DEM is reconditioned. Figure 3.34 AGREE DEM of Suriyawewa Terrain 57 Figure 3.35 HYDRO DEM of Suriyawewa 58 Figure 3.36 The theory behind Flow Accumulation Grid 59 Figure 3.37 Flow Direction Grid of Suriyawewa 60 Figure 3.38 Flow Accumulation Grid of Suriyawewa 61 Figure 3.39 Stream Grid of Suriyawewa generated by Stream Definition 63 Function overlaid on the Tributaries layer prepared by Survey Department of Sri Lanka. Figure 3.40 Stream Link Grid of Suriyawewa 64 Figure 3.41 Attributes Table of the Catchment Layer 65 Figure 3.42 Catchment Grid of Suriyawewa 66 Figure 3.43 Polygonal Catchment Layer of Suriyawewa 67 Figure 3.44 Drainage Points 68 Figure 3.45 Drainage Point Layer of Suriyawewa 69 Figure 3.46 Methodology followed to prepare the Hydrological Layers of 70 Suriyawewa Figure 3.47 Classification Statistics of Suriyawewa Slope Map 71 Figure 3.48 Slope Map of Suriyawewa 73 Figure 3.49 Reclassified Slope Map of Suriyawewa 74 Figure 3.50 Reclassified Slope Map of Suriyawewa (Converted to vector) 75 Figure 3.51 Adding a Text Field to the Catchment Layer and naming the 76 catchments Figure 3.52 Reclassified slope classes in Catchment ab 77 Figure 3.53 Average Annual Rainfall Map of Suriyawewa 78 Figure 3.54 The relationship between Head Difference and Slope Angle 79 Figure 3.55 Area calculations of the polygons in catchment ab by using its 80 attribute table Figure 3.56 The thirty selected catchments which drain the highest amount 83 of surface runoff on the basis of surface area and slope Figure 3.57 Reclasssified Rainfall Map of Suriyawewa 84 Figure 3.58 Reclasssified Rainfall Map of Suriyawewa (Converted to 85 polygonal feature class) Figure 3.59 Catchment ce with its rainfall classes 86 Figure 3.60 The fifteen catchments selected to harvest runoff water 88 considering rainfall, slope and surface area Figure 3.61 The fifteen catchments which yields the highest amount of 89 runoff with their outlet points Figure 3.62 Catchment cm 90 Figure 3.63 Catchment cf 91 Figure 3.64 Catchment bc 92 Figure 3.65 Catchment ce 92 Figure 3.66 Catchment cy 93 Figure 3.67 Catchment bd 94 Figure 3.68 Catchment ej 94 Figure 3.69 Catchment au 95 Figure 3.70 Happoruwa Wewa 96 Figure 3.71 View of downstream paddy fields from Happoruwa Wewa 96 Figure 3.72 Catchment bg 97 ix Figure 3.73 Catchment dm 97 Figure 3.74 Catchment cz 98 Figure 3.75 Catchment el 99 Figure 3.76 Catchment bp 99 Figure 3.77 Catchment bh 100 Figure 3.78 Catchment bj 101 Figure 3.79 Point D (230, E, 127, N) 102 Figure 3.80 Selected Locations 103 Figure 3.81 Geology Map of Suriyawewa 105 Figure 3.82 Paddy Fields at Location A 106 Figure 3.83 Paddy Fields at Location B 107 Figure 3.84 Paddy Fields at Location C 107 Figure 3.85 Ranmudu Wewa (left) and Maha Indi Wewa (right) 108 Figure 3.86 Chena cultivations near Point D 108 Figure 3.87 Irrigation Well - Suriyawewa 109 Figure 3.88 Suitable land use classes for groundwater recharging 111 Figure 3.89 Suitable slope classes for groundwater recharging 112 Figure 3.90 Suitable soil classes for groundwater recharging 113 Figure 3.91 Stream layer for groundwater recharging 113 Figure 3.92 Suitable rainfall classes for groundwater recharging 114 Figure 3.93 ArcGIS Model to select most suitable locations for 114 groundwater recharging Figure 3.94 Groundwater Recharge Potential Map 115 Figure 3.95 Figure 3.95: Potential areas for rooftop water harvesting 117 Figure 4.1 Annual runoff in percentage of annual rainfall as a function of 118 catchment size for small catchment (1 ha), medium-sized catchment (102 ha), and large catchment (104 ha) Figure 4.2 Catchment BH 122 Figure 4.3 Catchment BE, BC and BD 122 Figure 4.4 Proposed locations for water harvesting structures in Suriyawewa 125 x LIST OF TABLES Table 2.1 Advantages and disadvantages between using tank and cistern 7 for water storage Table 2.2 Reservoir capacity in Hambantota District 14 Table 2.3 Water Level of Hambantota Reservoirs (August 20 - August 26, ) Table 2.4 Water Level of Hambantota Reservoirs (September September 16, 2001) Table 2.5 Water Level of Hambantota Reservoirs (October 1- October 7, ) Table 2.6 Persons Affected by the Drought by District 17 (Information as at ) Table 3.1 1:50,000 topographical sheets covering Hambantota District 19 Table 3.2 Degree of Slope and Percent of Slope Values of some slope 28 angles Table 3.3 Field Visit Locations 32 Table 3.4 Defined Slope classes for the Suriyawewa Terrain 72 Table 3.5 Head difference of the Seven Slope Classes 79 Table 3.6 h x Area Calculation for Catchment ab 81 Table 3.7 The thirty selected catchments which drain the highest amount 82 of surface runoff according to the surface area and slopes Table 3.8 Classification of Suriyawewa Rainfall Map 82 Table 3.9 Weights defined for the rainfall classes 84 Table 3.10 Weight X Area calculation for Catchment ce 87 Table 3.11 The fifteen catchments selected to harvest runoff water 87 considering rainfall, slope and surface area. Table 3.12 Calculation of the summation of (Surface area x h) values 102 Table 3.13 Preferable conditions selected for groundwater recharging 115 Table 4.1 Capacity calculation of the four selected points 119 Table 4.2 Runoff capacity calculations for Suriyawewa DS Area 120 Table 4.3 Capacity calculations for Andara Wewa 120 Table 4.4 Predicted Capacities of the tanks at the four selected locations 120 xi
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