Preface | p. xi |
Acknowledgements | p. xv |
About the authors | p. xvii |
Symbols | p. xix |
Abbreviations | p. xxi |
Principles and practices of water harvesting | p. 1 |
Introduction | p. 1 |
Concept and definition of water harvesting | p. 2 |
History | p. 3 |
Components of water harvesting systems | p. 6 |
Importance and benefits of water harvesting | p. 7 |
Impact of global climate change and adaptation measures | p. 8 |
Hydrological aspects of water harvesting | p. 11 |
Introduction | p. 11 |
The hydrological cycle | p. 11 |
Small hydrological watershed model | p. 13 |
Hydrological characteristics | p. 13 |
Evapotranspiration | p. 14 |
Precipitation | p. 14 |
Frequency analysis and design rainfall | p. 16 |
Rainfall-runoff relationship | p. 18 |
Factors affecting runoff | p. 18 |
Soil type | p. 18 |
Rainfall characteristics | p. 18 |
Land cover | p. 18 |
Slope of the micro-catchment | p. 19 |
Size and shape of the micro-catchment | p. 19 |
Runoff models suitable for water harvesting | p. 20 |
Runoff models for micro-catchment water harvesting | p. 21 |
Runoff models for macro-catchment water harvesting | p. 26 |
Methods and techniques in water harvesting | p. 31 |
Introduction | p. 31 |
Classifications of water harvesting methods | p. 32 |
Micro-catchment water harvesting methods | p. 33 |
Rooftop and courtyard systems | p. 36 |
Suitable surfaces | p. 36 |
Issues to be addressed | p. 40 |
On-farm systems | p. 41 |
Inter-row water harvesting | p. 41 |
Negarim | p. 43 |
Meskat | p. 46 |
Contour bench terraces | p. 46 |
Small pits | p. 47 |
Contour bunds and ridges | p. 48 |
Semicircular and trapezoidal bunds | p. 51 |
Eyebrow terraces | p. 53 |
Rectangular bunds | p. 53 |
Vallerani-type micro-catchments | p. 55 |
Macro-catchment water harvesting techniques | p. 57 |
Introduction | p. 57 |
Long-slope water harvesting | p. 58 |
Hillside conduit systems | p. 58 |
Limans | p. 63 |
Large semicircular or trapezoidal bunds | p. 64 |
Cultivated tanks/reservoirs and hafairs | p. 64 |
Floodwater harvesting systems | p. 65 |
Wadi-bed water harvesting systems | p. 66 |
Off-wadi systems | p. 69 |
Harvesting water for animal consumption | p. 70 |
Traditional techniques | p. 70 |
Modern techniques | p. 71 |
Contamination concerns | p. 71 |
Runoff inducement methods | p. 73 |
Introduction | p. 73 |
Methods of improving runoff | p. 73 |
Creating shallow channels | p. 74 |
Clearing the catchment | p. 74 |
Smoothing the soil surface | p. 74 |
Compacting the soil surface | p. 75 |
Surface sealing | p. 77 |
Impermeable coverings | p. 78 |
Advantages and disadvantages of runoff-inducement methods | p. 83 |
Further considerations | p. 84 |
Identification of areas suitable for water harvesting | p. 87 |
Introduction | p. 87 |
Parameters for identifying suitable areas | p. 87 |
Rainfall characteristics | p. 87 |
Hydrology and water resources | p. 89 |
Vegetation and land use | p. 90 |
Topography, soil type and soil depth | p. 90 |
Socioeconomics and infrastructure | p. 92 |
Methods of data acquisition | p. 93 |
Overview | p. 93 |
Ground truthing | p. 93 |
Aerial photography | p. 94 |
Satellite and remote-sensing technology | p. 94 |
Tools | p. 98 |
Maps | p. 98 |
Topographic maps | p. 98 |
Thematic maps | p. 98 |
Aerial photographs | p. 98 |
Geographic information systems | p. 98 |
Decision trees | p. 103 |
Planning and design of water harvesting systems | p. 105 |
Introduction | p. 105 |
Soil-water-plant-climate relations | p. 105 |
Soil | p. 105 |
Texture and structure | p. 106 |
Water-holding capacity and soil depth | p. 106 |
Infiltration rate | p. 108 |
Crop water requirements | p. 108 |
Plant and drought | p. 109 |
Estimating crop water needs | p. 110 |
Field water budget | p. 112 |
Rainfall | p. 117 |
Inter-seasonal distribution of rainfall | p. 117 |
Design rainfall | p. 117 |
Need for storage | p. 119 |
Basic design procedure | p. 119 |
Selection of site and method | p. 121 |
Selection of crops | p. 123 |
Runoff estimation | p. 124 |
Catchment: Cropping area ratio (CCR) | p. 124 |
Design examples | p. 125 |
Optimization of system design | p. 126 |
Further considerations in area ratio selection | p. 126 |
Design considerations for trees | p. 128 |
Design for trees | p. 128 |
Life-saving harvested water | p. 129 |
Dimensioning, materials and estimation of quantities | p. 129 |
Dimensioning and system layout | p. 129 |
Bund earthwork | p. 133 |
Earthwork balance | p. 135 |
Storage of harvested water | p. 137 |
Introduction | p. 137 |
Soil profile | p. 138 |
Above ground storage | p. 140 |
Surface/ground storage | p. 143 |
Small storage ponds | p. 144 |
Small farm reservoirs | p. 144 |
Tanks | p. 145 |
Hafairs | p. 148 |
Large reservoirs | p. 149 |
Subsurface/underground storage | p. 149 |
Cisterns | p. 149 |
Lining water storage structures | p. 155 |
Groundwater dams | p. 156 |
Sand-storage dams | p. 156 |
Percolation dams | p. 157 |
Subsurface dams | p. 158 |
Selection of storage system | p. 160 |
Implementation, operation, and maintenance of water harvesting systems | p. 163 |
Introduction | p. 163 |
Implementing water harvesting systems | p. 163 |
Considerations in implementation | p. 167 |
Over-design and under-design issues | p. 168 |
Appropriate technology | p. 169 |
Operating water harvesting systems | p. 170 |
Maintaining water harvesting systems | p. 172 |
Monitoring and evaluation | p. 173 |
Extension and training | p. 177 |
Socioeconomic issues | p. 183 |
Introduction | p. 183 |
Social feasibility studies | p. 183 |
Land-tenure issues | p. 184 |
Analyzing costs and benefits of water harvesting | p. 184 |
Costs in water harvesting | p. 185 |
Benefits of water harvesting | p. 186 |
Economic feasibility analysis | p. 187 |
Micro-catchments for field crops | p. 188 |
Macro-catchments in sub-Saharan Africa | p. 189 |
Examples from China and India | p. 190 |
Some general recommendations | p. 191 |
Integrated approach to planning and management | p. 191 |
The role of government agencies | p. 193 |
Community participation | p. 193 |
Gender representation | p. 195 |
Farmers as managers | p. 195 |
The role of experts and donor agencies | p. 196 |
Adoption or non-adoption of interventions | p. 197 |
Water harvesting and sustainability in agriculture | p. 198 |
Resource sustainability | p. 199 |
Ecological sustainability | p. 200 |
Social sustainability | p. 200 |
Other sustainability aspects | p. 201 |
Economic sustainability | p. 201 |
Technological sustainability | p. 201 |
Political sustainability | p. 201 |
Water quality and environmental considerations | p. 203 |
Introduction | p. 203 |
Water harvested for human consumption | p. 203 |
Water harvested for animal consumption | p. 204 |
Water harvested for crop production | p. 206 |
Water quality considerations | p. 207 |
Rooftop and courtyard systems | p. 207 |
Runoff water from on-farm micro-catchment systems | p. 211 |
Long-slope water harvesting | p. 211 |
Floodwater harvesting | p. 212 |
Impacts on downstream ecosystems and biodiversity | p. 214 |
Water-borne diseases | p. 215 |
References | p. 217 |
Index | p. 227 |
Color plates | p. 237 |
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