Since in large parts of the world it is getting difficult to meet growing water demands by mobilising more water, the discourse has turned its focus to demand management, governance and the necessary concern for aquatic ecosystems by reserving an "environmental flow" in the river. The latter calls for attention to river depletion which may be expected in response to changes in consumptive water use by both natural and anthropogenic systems. Basically, consumptive use has three faces: runoff generation influenced by land cover changes; consumptive use of water withdrawn; and evaporation from water systems (reservoirs, canals, river based cooling). After demonstrating the vulnerability to changes in consumptive use under savanna region conditions - representative of many poverty and hunger prone developing countries subject to attention in the Millennium Development Goal activities - the paper exemplifies; 1) changes in runoff generation in response to regional scale land cover changes; 2) consumptive use in large scale irrigation systems. It goes on to analyse the implications of seeing food as a human right by estimating the additional consumptive use requirements to produce food for the next two generations. Attention is paid to remaining degrees of freedom in terms of uncommitted water beyond an environmental flow reserve and to potential food trade consequences (so-called virtual water). The paper concludes that a human-right-to-food principle will have major consequences in terms of altered consumptive water use. It will therefore be essential for humanity to address river depletion to avoid loss of resilience of the life support system. This will demand a deep-going cooperation between hydrology, ecology and water governance.Since in large parts of the world it is getting difficult to meet growing water demands by mobilising more water, the discourse has turned its focus to demand management, governance and the necessary concern for aquatic ecosystems by reserving an "environmental flow" in the river. The latter calls for attention to river depletion which may be expected in response to changes in consumptive water use by both natural and anthropogenic systems. Basically, consumptive use has three faces: runoff generation influenced by land cover changes; consumptive use of water withdrawn; and evaporation from water systems (reservoirs, canals, river based cooling). After demonstrating the vulnerability to changes in consumptive use under savanna region conditions - representative of many poverty and hunger prone developing countries subject to attention in the Millennium Development Goal activities - the paper exemplifies; 1) changes in runoff generation in response to regional scale land cover changes; 2) consumptive use in large scale irrigation systems. It goes on to analyse the implications of seeing food as a human right by estimating the additional consumptive use requirements to produce food for the next two generations. Attention is paid to remaining degrees of freedom in terms of uncommitted water beyond an environmental flow reserve and to potential food trade consequences (so-called virtual water). The paper concludes that a human-right-to-food principle will have major consequences in terms of altered consumptive water use. It will therefore be essential for humanity to address river depletion to avoid loss of resilience of the life support system. This will demand a deep-going cooperation between hydrology, ecology and water governance.

This article analyzes the water implications in 92 developing countries of first attaining the 2015 hunger target of the United Nations Millennium Development Goals and then feeding a growing population on an acceptable standard diet. The water requirements in terms of vapor flows are quantified, potential water sources are identified, and impacts on agricultural land expansion and water tradeoffs with ecosystems are analyzed. This article quantifies the relative contribution from infiltrated rainwater/green water in rain-fed agriculture, and liquid water/blue water from irrigation, and how far water productivity (WP) gains can go in reducing the pressure on freshwater resources. Under current WP levels, another 2,200 km3·yr−1 of vapor flow is deemed necessary to halve hunger by 2015 and 5,200 km³·yr⁻¹ in 2050 to alleviate hunger. A nonlinear relationship between vapor flow and yield growth, particularly in low-yielding savanna agro-ecosystems, indicates a high potential for WP increase. Such WP gains may reduce additional water needs in agriculture, with 16% in 2015 and 45% by 2050. Despite an optimistic outlook on irrigation development, most of the additional water will originate from rain-fed production. Yield growth, increasing consumptive use on existing rain-fed cropland, and fodder from grazing lands may reduce the additional rain-fed water use further by 43–47% until 2030. To meet remaining water needs, a cropland expansion of ≈0.8% yr⁻¹, i.e., a similar rate as over the past 50 years (≈0.65% yr⁻¹), seems unavoidable if food production is to occur in proximity to local markets.

Intensive irrigation development brought the Bhavani basin in southern India to 'allocation closure' in the 1950s, with all available surface water being assigned to various uses. In spite of this, policies and investments have supported further intensified water use, some well planned, but many unplanned from a basin perspective. At present, individuals acting independently and domestic water schemes are important drivers. The basin is moving towards 'hydrologic closure', with little water leaving the basin. While agriculture in the basin is showing no signs of collapse, people are demanding more water, leading to a 'perception-wise' closure. The changes in use and perception underscore the need for a basin-wide perspective that considers consumptive water use as well as river diversions.

Mainstream views of water resource development focus on conventional concepts of supply and demand and often conceive of river basin development as a linear and rational process of harnessing nature and developing water for human use. However, human-environment interactions are more complex and the way societies respond to water challenges is shaped by a number of cultural, environmental, economic and political factors. Using river basin case studies in a variety of contexts, this book provides an overview of how societies have gradually developed their water resources and furthers our understanding of how such resources can be managed successfully or unsuccessfully. Discussing how and why particular options are selected, and why a particular course of events eventually prevails, the book stresses the importance of context and a multidisciplinary approach in moving towards sustainable and equitable development.

This study explores the theory and practice of Adaptive Management (AM) based on a detailed field study. To what extent farmers and water resource managers already practice AM; and whether it is practiced in an optimal manner or could there be areas for improvement based on recent advancements in the theory of AM; are some of the questions that are particularly appropriate in the light of rapid changes in river basin water use and also in relation to basin closure.

This paper draws on the development and use of water resources in the Lower Bhavani Project (LBP), with the LBP reservoir and the 84,000 hectare (ha) LBP command area. The project diverts water from the Bhavani River, a tributary of the Cauvery River, in the South Indian state of Tamil Nadu. The LBP was the first major irrigation project initiated in India after independence in 1947 and was in full operation by 1956. The LBP has had a major impact on the socioeconomic development of the area, and continues to be a productive irrigated area. However, behind the story of a productive irrigation system lie more complex stories of societal change, conflicts and negotiation in response to water scarcity and several drivers of change. In fact, there were problems from the start, as the original design concept for the project was not accepted by farmers who opted for more waterintensive crops rather than the suggested ‘dry crops’. In addition, a highly fluctuating climate and the transfer of water to urban areas have all been a challenge for agricultural producers. Farmers, system managers and others have responded to these challenges by trying out different management systems, and have continued to adjust their practices in the face of change.

This paper presents a five-step framework of analysis based on recent theories of AM to understand the extent to which it is practiced and how it could be improved. The Adaptive Water Management (AWM) analysis shows that the LBP system has increasingly fulfilled the criteria of a complex adaptive system over the years. Social learning takes place at system and farmer level. The main uncertainty factor, rainfall variability, has been considered in a stepwise way during the system change cycles and has been included in the system design. The system has, to some extent, fulfilled the requirement of an adaptive regime and has built a substantial amount of social capital. This has been a rather ad hoc process, which could have been much faster had attention been paid to institutional setups and infrastructure designs that support AM.

However, the future will not be easier. The basin is closed with water resources already overallocated to various uses. Yet, cities and industries, and users outside the basin, will demand more and agriculture itself is becoming less important to the economy. To meet these future challenges, it is essential that policymakers recognize and build on the existing social capital and the negotiation and learning systems that have been developed.

Finally, the LBP case study gives us some hope. In spite of contending with an imperfect irrigation system design and intense competition for water resources, water resource managers and farmers are able to adapt and continue to reap benefits from a productive agricultural system.