Abstract: Fresh water is a finite and a vulnerable resource that sustains life, development, and the environment. Approximately 80% of the world’s cultivable land depends on rainfall, interestingly rain-fed production produces up to 70% of the global food supply yet it’s the same system that has been threatened with frequent dry spells and long term droughts. Estimates show that uncertain weather conditions and insufficient water for irrigation could lead agricultural productivity in several countries to fall by up to 50% over the next decade, severely affecting their prospects of greater social and economic development. Rainwater harvesting is the collection and storage of any farm water either runoff or creek flow for irrigation use. Rainwater harvesting for supplemental irrigation is currently the best practice to mitigate the escalating issue of water shortage caused by concurrent agricultural droughts. One form of mitigating the negative effects of such droughts and dry spells is the establishment of small scale simple low cost supplemental irrigation schemes in rain-fed agriculture. This is to reduce the extent of crop failures and as well increase the water use efficiency WUE of crops. In a developing country like Uganda where more than 80% of the population lives in rural areas and their lives depends on rain-fed agriculture. Droughts and dry spells have greater consequences to the peoples’ survival and development. This study presents a sustainable economic solution for the problem of crop yield reduction due to short droughts during the rainy season, more particularly for maize as a staple crop. It aims at reducing maize crop failures by supplying supplemental irrigation during the critical growth stages of the plant. It employs FAO’s water productivity model (Aquacrop) to estimate and predict the potential economic benefits of supplemental irrigation as well as the cost benefit analysis to examine the optimization of the supplemental system. Results show that applying supplemental irrigation in case of low soil moisture during the critical stages of maize can have greater crop yield increments. Optimization of the system is achieved when a farmer sacrifices about 5% of his hectare piece of land to establish a runoff lined storage pond of 800 cubic meters by volume along with a diesel pump for water lifting using furrow irrigation. Using such volume of PVC lined pond covered with a natural mat of growing Azolla plant on the water surface can give optimum yields on a one hectare crop land. Azolla, the aquatic floating fern has multi benefits, however, its primary importance in this study is keeping the water pond environmentally safety. The proposed supplemental irrigation scheme has a payback period of 6 years.

Agriculture in Sub-Saharan Africa is constrained by highly variable rainfall, frequent drought and low water productivity. There is an urgent need, heightened by climate change, for appropriate technologies to address this problem through managing and increasing the quantity of water on farmers’ fields – water harvesting. This book defines water harvesting as a set of approaches which occupy an intermediate position along the water-management spectrum extending from in situ moisture conservation to irrigated agriculture. They generally comprise small-scale systems that induce, collect, store and make use of local surface runoff for agriculture. The authors review development experience and set out the state of the art of water harvesting for crop production and other benefits in Sub-Saharan Africa. This includes an assessment of water harvesting schemes that were initiated two or three decades ago when interest was stimulated by the droughts of the 1970s and 1980s. These provide lessons to promote sustainable development of dryland agriculture in the face of changing environmental conditions. Case studies from eight countries across Sub-Saharan Africa provide the evidence base. Each follows a similar format and is based on assessments conducted in collaboration with in-country partners, with a focus on attempts to promote adoption of water harvesting, both horizontally (spread) and vertically (institutionalization). Introductory cross-cutting chapters as well as an analytical conclusion are also included.

Dry areas suffer not only from limited rainfall but also ‘natural leakage’—90% of rainwater is lost directly or indirectly, and is unavailable for agriculture or domestic use. Water harvesting is a low-cost, easy-to-use, environmentally-friendly way to recover a large part of this lost water. How does water harvesting work? Which sites or areas are best suited and how can these areas be identified? How to design, build and maintain a water harvesting system tailored to local needs? How can water harvesting contribute to combating land degradation, enhancing food security and adapting to climate change? This book provides the answers. The book is based on many years of research, training and development by three of the world’s leading experts in water management and agriculture. It is authoritative, comprehensive, and easy to read, containing practical examples, many illustrations and little jargon. This volume will be of great interest to researchers, development workers, farmers, policymakers, students of the natural sciences—in fact, anyone interested in efficient, sustainable management of water resources and agriculture.

This paper provides an overview of innovative options for developing and using water for food production in sub-Saharan Africa (SSA) in light of the growing scarcity and competition for water resources. These options include rainwater harvesting, selective development of wetlands for agriculture, exploitation of shallow groundwater, and recycling urban waste. The options are largely based on low-cost individualized technologies, which lend themselves to private-sector promotion.Water-demand management approaches are also discussed.

This report examines specific water harvesting systems in sub-Saharan Africa. Case studies of thirteen systems from six different countries are presented, and conclusions are drawn under the headings of techniques and engineering, production, socio-economic and project management aspects. A number of projects throughout the region, set up in the 1980's, have included water harvesting components. However, there is a wide range of techniques, approaches and costs - and the impact of these projects varies considerably. The majority of systems introduced are for crop production, but there are examples of water harvesting to establish trees in dry areas and for rehabilitation of grazing land also. The need for voluntary participation in all stages of project development is highlighted. It is evident that without this participation there is little or no chance of widespread adoption. The importance of indigenous systems of water harvesting, and their potential role as a base for planning, is stressed in the conclusions.

This report examines specific water harvesting systems in sub-Saharan Africa. Case studies of thirteen systems from six different countries are presented, and conclusions are drawn under the headings of techniques and engineering, production, socio-economic and project management aspects. A number of projects throughout the region, set up in the 1980's, have included water harvesting components. However, there is a wide range of techniques, approaches and costs - and the impact of these projects varies considerably. The majority of systems introduced are for crop production, but there are examples of water harvesting to establish trees in dry areas and for rehabilitation of grazing land also. The need for voluntary participation in all stages of project development is highlighted. It is evident that without this participation there is little or no chance of widespread adoption. The importance of indigenous systems of water harvesting, and their potential role as a base for planning, is stressed in the conclusions.

D ryland regions in Sub-Saharan Africa are home to one-half of the region’s population and three-quarters of its poor. Poor both in natural resources and in assets and income, the inhabitants of drylands are highly vulnerable to droughts and other shocks. Despite a long history of interventions by governments, development agencies, and civil society organizations, there have been no sustained large-scale successes toward improving the resilience of drylands dwellers. Improved Agricultural Water Management for Africa’s Drylands describes the extent to which agricultural water management interventions in dryland regions of Sub-Saharan Africa can enhance the resilience and improve the well-being of the people living in those regions, proposes what can realistically be done to promote improved agricultural water management, and sets out how stakeholders can make those improvements. After reviewing the current status of irrigation and agricultural water management in the drylands, the authors discuss technical, economic, and institutional challenges to expanding irrigation. A model developed at the International Food Policy Research Institute is used to project the potential for irrigation development in the Sahel Region and the Horn of Africa. The modeling results show that irrigation development in the drylands can reduce vulnerability and improve the resilience of hundreds of thousands of farming households, but rainfed agriculture will continue to dominate for the foreseeable future. Fortunately, many soil and water conservation practices that can improve the productivity and ensure the sustainability of rainfed cropping systems are available. The purpose of this book is to demonstrate the potentially highly benefi cial role of water and water management in drylands agriculture in association with agronomic improvements, market growth, and infrastructure development, and to assess the technological and socioeconomic conditions and institutional policy frameworks that can remove barriers to adoption and allow wide-scale take-up of improved agricultural water management in the dryland regions of Sub-Saharan Africa.