Studies the low-cost alternative strategy of selective lining of watercourses to reduce seepage and increase irrigated areas in the Indian subcontinent. Satellite remote-sensing (SRS) is seen as a cost-effective evaluation tool in view of its large area of synoptic and repetitive coverage.

The cost of developing new irrigation potential is escalating. A low-cost alternative strategy of selective lining of watercourses to reduce seepage and increase irrigated area is being increasingly adopted in the Indian subcontinent. However, studies on assessing the efficacy of such lining are few. These studies have depended mainly on a few sample watercourses suppor1ed by limited water measurement and agricultural data, and their results are not conclusive. Satellite Remote Sensing (SRS) is seen as a cost-effective evaluation tool in view of its large area of coverage, which is synoptic and repetitive. The analysis of multiyear satellite data has enabled to evaluate the lining efficacy of about 30 watercourses located in the fresh, marginal and saline groundwater zones of the Bhakra canal command in Haryana, India. The lined watercourses together with concomitant groundwater development and use have sustained tail-to-head uniformity of water distribution even after 20 years of lining. The SRS technique can be used as a stand-alone tool in an environment where only small amounts of groundwater supplies are used to support surface water supplies. In areas with substantial groundwater supplies, isolation of lining efficacy will require additional data on groundwater support. The SRS technique is particularly useful as a screening tool to identify problem watercourses where field verification data can be collected for cost-effective and quick evaluation of watercourse lining. The cost of using this technique works out to only US$0.17 per hectare of the area served by the watercourses. This cost is based on the 1996 cost of satellite images, covering a geographic area of about 225 square kilometers.

A clear understanding of the current water balance is required to explore options for water saving measures. However, measurement of all the terms in the water balance is infeasible in terms of spatial and temporal scale, but hydrological simulation models can fill the gap between measured and required data. For a basin in Western Turkey, simulation modeling at three different scales, field, irrigation scheme and basin scale, was performed to obtain all terms of the water balance. These water balance numbers were used to calculate the Productivity of Water at the three spatial levels distinguished to assess the performance of the systems.

Discusses and illustrates concepts for identifying ways of improving productivity of water within basins. The results of applying a water accounting procedure to four sub-basins in South Asia (Bhakra in India; Chishtian in Pakistan; Huruluwewa in nothern Sri Lanka; and Kirindi Oya in southern Sri Lanka) are presented. The methodology used identifies the quantities and productivity of various uses of water within a basin. This information is then used to identify the water-saving potential, and the means of improving the productivity of the managed supplies.

This volume is an analytical summary and a critical synthesis of research at the International Water Management Institute over the past decade under its evolving research paradigm known popularly as 'more crop per drop'. The research synthesized here covers the full range of issues falling in the larger canvas of water-food-health-environment interface. Besides its immediate role in sharing knowledge with the research, donor, and policy communities, this volume also has a larger purpose of promoting a new way of looking at the water issues within the broader development context of food, livelihood, health and environmental challenges. More crop per drop: Revisiting a research paradigm contrasts the acquired wisdom and fresh thinking on some of the most challenging water issues of our times. It describes new tools, approaches, and methodologies and also illustrates them with practical application both from a global perspective and within the local and regional contexts of Asia and Africa. Since this volume brings together all major research works of IWMI, including an almost exhaustive list of citations, in one single set of pages, it is very valuable not only as a reference material for researchers and students but also as a policy tool for decision-makers and development agencies.

Smallholder irrigation systems–where farm sizes generally range from a fraction of a hectare to 10 hectares–pose special management problems, especially where the water available for irrigation is frequently less than the demand. The intensity of system adjustments required to meet individual farmer demands, and the administrative complexity of measuring and accounting water deliveries have generally proven excessive when attempting to meet “on demand” schedules, resulting in chaos (often characterized by illegal tampering with infrastructure, and vast differences of water use intensity at different locations in the system). The alternative–provision of a simple service, based on proportional sharing of available supplies on the basis of landholdings–has been resilient for many years over vast areas. The approach is based on a clear delineation between the part of the irrigation system that is actively managed (at various flow rates and water levels) and the part of the system that operates either at full supply level (with proportional division of water down to the level at which farmers rotate among their individual farms), or is completely shut. This operational design is known as a “structured” system, and has well-defined hydraulic characteristics, simplifying operation and management, in turn allowing a clearer definition of water entitlements and the responsibilities of agency staff and farmers. The approach is particularly suited to areas where water is scarce and discipline is needed to ration water among users. An additional benefit, which has been demonstrated in modeling studies using a well–proven model relating to water and yield, is that the productivity of water (which is more important than the more traditional productivity of land when water is scarce) is substantially increased when deficit irrigation is practiced–a widely observed and predictable response to rationed water supplies. Structured systems are most suited where water is scarce, clear definition of water entitlements is needed, management capacity is limited, and investment resources are limited. The approach to determining critical aspects of a structured system design is described in this report.

Although irrigation projects often provide water for more than crop irrigation, water allocation and management decisions often do not account for nonirrigation uses of water. Failure to account for the multiple uses of irrigation water may result in inefficient and inequitable water allocation decisions. Decision-makers often lack information on the relative economic contributions of water in irrigation and nonirrigation uses. This report addresses this problem. It examines the relative economic contributions of irrigated agriculture and reservoir fisheries in the Kirindi Oya irrigation system, located in Southeastern Sri Lanka. The results of the analysis indicate the importance of both irrigated paddy production and reservoir fisheries to the local economy. They also demonstrate significant potential financial and economic gains to irrigated agriculture from improvements in water management practices. Since these water uses are interdependent, policy makers must consider how changes in water management practices may affect reservoir levels and water quality and the fisheries that depend on them.

In this report, the concept and procedures of hydronomic (hydro water + nomus management) zones are introduced. A set of six hydronomic zones are developed and defined based on key differences between reaches or areas of river basins. These are the: Water Source Zone, Natural Recapture Zone, Regulated Recapture Zone, Stagnation Zone, Final Use Zone, and Environmentally Sensitive Zone. The zones are defined based on similar hydrological, geological and topographical conditions and the fate of water outflow from the zone. In addition, two conditions are defined which influence how water is managed: whether or not there is appreciable salinity or pollution loading; and whether or not groundwater that can be used for utilization or storage is present. Generic strategies for irrigation for four water management areas, the Natural Recapture, Regulated Recapture, Final Use, and Stagnation Zones, are presented. The Water Source Zone and Environmentally Sensitive Zone are discussed in terms of their overall significance in basin water use and management.

This book is a collection of overview articles showing how space-based observations, combined with hydrological modeling, have considerably improved our knowledge of the continental water cycle and its sensitivity to climate change. Two main issues are highlighted: (1) the use in combination of space observations for monitoring water storage changes in river basins worldwide, and (2) the use of space data in hydrological modeling either through data assimilation or as external constraints. The water resources aspect is also addressed, as well as the impacts of direct anthropogenic forcing on land hydrology (e.g. ground water depletion, dam building on rivers, crop irrigation, changes in land use and agricultural practices, etc.). Remote sensing observations offer important new information on this important topic as well, which is highly useful for achieving water management objectives.Over the past 15 years, remote sensing techniques have increasingly demonstrated their capability to monitor components of the water balance of large river basins on time scales ranging from months to decades: satellite altimetry routinely monitors water level changes in large rivers, lakes and floodplains. When combined with satellite imagery, this technique can also measure surface water volume variations. Passive and active microwave sensors offer important information on soil moisture (e.g. the SMOS mission) as well as wetlands and snowpack. The GRACE space gravity mission offers, for the first time, the possibility of directly measuring spatio-temporal variations in the total vertically integrated terrestrial water storage. When combined with other space observations (e.g. from satellite altimetry and SMOS) or model estimates of surface waters and soil moisture, space gravity data can effectively measure groundwater storage variations. New satellite missions, planned for the coming years, will complement the constellation of satellites monitoring waters on land. This is particularly the case for the SWOT mission, which is expected to revolutionize land surface hydrology. Previously published in Surveys in Geophysics, Volume 37, No. 2, 2016