Water resources are already very scarce. With further demand from population growth, dietary changes, biofuel production, urbanisation and climate change, it will be extremely difficult to find enough supply to enable an increase in global food production by 70 per cent. There are, however, potential solutions that involve increasing water productivity, improved water storage, more irrigation and re-using waste water. But current investment levels in overseas development aid and spending at country level are unlikely to be sufficient to ensure food security in the relatively short- term, let alone by 2050, when the global population is forecast to be nine billion. This article describes some of the issues that have to be faced to deliver food security and overcome water scarcity, and how these improvements can be achieved through a combination of science, policy and investment.

Water scarcity is already a reality. More food will be required for a growing and wealthier and urbanized population that will put more pressure on water resources. With several water-related limits reached or breached - groundwater decline, shrinking rivers and threatened fisheries - we must ask, 'Will there be enough water to grow enough food? It is possible to produce the food needed, but if present practices continue it is not probable that we will solve the many poverty and environmental challenges confronting us. To share a scarce resource and to limit environmental damage in the face of climate change, it is imperative to limit future water use. Important pathways to growing enough food with limited water are to increase productivity of water in irrigated and rainfed areas, improve water management in low-yielding rainfed areas, and to consider our own food consumption patterns. In pockets of poverty in Sub-Saharan Africa and Asia, expanding access to water through a range of water management solutions holds the key to food security and poverty reduction. For sustainable water use, water managers must consider agriculture as an ecosystem and how other ecosystem services are impacted through water. These actions will require serious changes in how we think about water and food, and how we govern water and land resources.

"The impacts of climate change on the global hydrological cycle are expected to vary the patterns of demand and supply of water for agriculture -- the dominant user of freshwater. The extent and productivity of both irrigated and rainfed agriculture can be expected to change. As a result, the livelihoods of rural communities and the food security of a predominantly urban population are at risk from water-related impacts linked primarily to climate variability. The rural poor, who are the most vulnerable, are likely to be disproportionately affected. Adaptation measures that build upon improved land and water management practices will be fundamental in boosting overall resilience to climate change. And this is not just to maintain food security: the continued integrity of land and water systems is essential for all economic uses of water. This report summarizes current knowledge of the anticipated impacts of climate change on water availability for agriculture and examines the implications for local and national food security. It analyses expected impact of climate change on a set of major agricultural systems at risk and makes the case for immediate implementation of 'no-regrets' strategies which have both positive development outcomes and make agricultural systems resilient. It is hoped that policy makers and planners can use this report to frame their adaptation responses when considering both the water variable in agriculture and the competing demands from other users"--Page 4 of cover.

Water scarcity is already a reality. More food will be required for a growing and wealthier and urbanized population that will put more pressure on water resources. With several water-related limits reached or breached - groundwater decline, shrinking rivers and threatened fisheries - we must ask, Will there be enough water to grow enough food? It is possible to produce the food needed, but if present practices continue it is not probable that we will solve the many poverty and environmental challenges confronting us. To share a scarce resource and to limit environmental damage in the face of climate change, it is imperative to limit future water use. Important pathways to growing enough food with limited water are to increase productivity of water in irrigated and rainfed areas, improve water management in low-yielding rainfed areas, and to consider our own food consumption patterns. In pockets of poverty in sub-Saharan Africa and Asia, expanding access to water through a range of water management solutions holds the key to food security and poverty reduction. For sustainable water use, water managers must consider agriculture as an ecosystem and how other ecosystem services are impacted through water. These actions will require serious changes in how we think about water and food, and how we govern water and land resources.

Water is life and is one of the major inputs for agriculture. Earth has a finite supply of fresh water and therefore, demands that every drop of annual rainfall should be conserved and judiciously utilized for production and postproduction agriculture to get maximum nutrients per unit of water. The concept of water productivity in agriculture is now shifting from harvest index per unit of land and water to nutrients (protein, carbohydrate, fat, etc.) produced per unit of water. This varies with food commodities and locations. For example, the total dietary energy produced by potato, maize, peanut, wheat, milk, egg and beef using one m³ of water are about 5600 kcal, 3800 kcal, 2300 kcal, 2280 kcal, 660 kcal, 520 kcal and 100 kcal, respectively. Similarly, the production of protein using one m³ of water by potato, peanut, maize, wheat, egg, milk, chicken, and beef are 150 g, 111 g, 77 g, 74 g, 41 g, 40 g, 33 g and 10 g, respectively. This paper describes the water nutrient productivity of some of the crops and livestock products and suggests as to how to provide food and nutritional security through an appropriate and balanced diet design, to the maximum number of people of the world from the limited and dwindling land, water and bio resources.