Mobin-ud-Din Ahmad

Measuring and enhancing the value of agricultural water in irrigated river basins

This paper provides an overview of the issues in and approaches to measuring and enhancing the value of agricultural water in large irrigated river basins. It develops a framework and a set of indicators for valuing agricultural water by looking into various dimensions and underlying key factors that influence the value of water at micro, meso and macro levels. The indicators are applied to recent, primary- and secondary-level empirical data from the Indus basin Irrigation system of Pakistan. In addition, the paper compiles recent estimates of the value of agricultural water from 40 settings in 23 countries. Finally, the paper outlines measures for enhancing the value of agricultural water. The paper makes four main points: (1) The popular productivity indicators based on crop output do not capture the full range of benefits and costs associated with agricultural water use. (2) The value of agricultural water may not be as low as it is generally perceived or estimated when all major uses and direct and indirect benefits of water at various levels are properly accounted for. (3) The value of water varies across time and space, and the value to stakeholders at various scales (farmer, system manager, basin planner and national policy maker) could be quite different. For example, the estimate of agricultural water value in the upper Indus basin in Pakistan varies from US

Producing more food with less water in a changing world: assessment of water productivity in 10 major river basins

0.04/m3 at the farm scale to US

Mapping basin-level water productivity using remote sensing and secondary data in the Karkheh River Basin, Iran

0.22/m3 at the national scale. The farm-scale value is more relevant, e.g., for agricultural water charging policies, but for water-sector investments and allocation decisions, the national-scale value is important. The decision-making processes related to water sector investments, allocations, management, and charging/cost recovery schemes could be potentially misguided if key dimensions of water value that are related to water availability and use, benefits/costs, and temporal and spatial aspects are not properly accounted for in valuation. (4) Efforts should be directed not only at increasing the productivity of water in terms of mass of output per unit of water, but also the overall benefits or value of water at various levels for larger growth and poverty alleviation impacts, considering the sustainability of the systems.

The impact of climate change on regional water balances in Bangladesh

This article summarizes the results of water productivity assessment in 10 river basins across Asia, Africa and South America, representing a range of agro-climatic and socio-economic conditions. Intensive farming in the Asian basins gives much greater agricultural outputs and higher water productivity. Largely subsistence agriculture in Africa has significantly lower water productivity. There is very high intra-basin variability, which is attributed mainly to lack of inputs, and poor water and crop management. Closing gaps between “bright spots” and the poorly performing areas are the major tasks for better food security and improved livelihoods, which have to be balanced with environmental sustainability.

The Karkheh River basin: the food basket of Iran under pressure

This article deals with water productivity (WP) assessment at a range of spatial scales for the Karkheh Basin, Iran. Sub-catchment to basin-scale estimates are based on an innovative method that uses readily available satellite images and routine secondary data. The farm-scale results are derived from the field survey of 298 farmers. The results show large variations in the WP, which indicate considerable scope for improvement. Inclusion of livestock changes both the magnitude and patterns of overall WP at the sub-catchment scale. This stresses the need for holistic accounting of all agricultural enterprises in water (re)allocation policies.

Upscaling water productivity in irrigated agriculture using remote-sensing and GIS technologies

The probable effect of climate change on the water available for use in Bangladesh is not well known. We calculate monthly water balances for five main regions of Bangladesh to examine the likely impacts of climate change to 2050. We also examine the impact of past and potential future irrigation development. Climate change projections for rainfall in Bangladesh are uncertain, with increased rain in the wet season likely, but decreased rain also possible. Runoff is projected to vary in a manner similar to rainfall. However, assuming no change to the area of crops, all projections result in increases in irrigation water use, which leads to groundwater level declines. The impact of change (whether climate change or development) on water availability and use is greater in the Northwest region than elsewhere. For most water balance terms in most regions, irrigation development (both historic and future) is calculated to have a larger impact than climate change. Climate change is calculated to have a larger impact than irrigation development only on evapotranspiration and runoff, and possibly on groundwater levels. Model sensitivity tests suggest that model uncertainty is less than climate change uncertainty. To reverse lowered groundwater levels, Bangladesh’s policy includes greater use of surface water. While we calculate groundwater levels will rise, the viability of the policy may be affected by future changes to upstream use.

Satellite surveillance of evaporative depletion across the Indus Basin

Development of the Karkhehs water resources has contributed in important ways to Irans food security and underpinned the livelihoods of both basin farmers and urban consumers. However, the linkages between poverty and agricultural water use in the basin are now weak at best. Furthermore, there is now little if any additional water to develop. As a result, future water policy will need to increasingly focus on management and allocation of existing resources rather than development of new sources of supply, and poverty reduction strategies may need to aim outside agricultural water solutions.

Reviewing SEBAL input parameters for assessing evapotranspiration and water productivity for the Low-Middle São Francisco River basin, Brazil: Part A: Calibration and validation.

Reliable information on water depletion for agricultural production is much needed when freshwater resources are getting scarcer. This is the case in the irrigated Indus basin. Despite their importance, data required to monitor the productivity of the land and water resources over vast areas are usually not available or accessible. Satellite measurements from the National Oceanic and Atmospheric Adminstration (NOAA) weather satellite are combined in this study with ancillary in situ data into a geographic information system (GIS). Remote-sensing measurements are converted to crop yield, to actual evapotranspiration and, indirectly, to net groundwater use. The GIS data consist of canal-water deliveries and rainfall records. For each of the canal commands, the productivity of water is calculated. Large variability in the data is found from the different canal commands in the Indus basin. It is concluded that water productivity is controlled more by crop yields than by the water input. The spatial variability of productivity per unit water diverted is greater than per unit depleted. This can be ascribed to wide variations in the relationship between canal-water supply and actual evapotranspiration. This is an issue covered by classical irrigation efficiencies. Upscaling of water productivity for the Indus basin was achieved by aggregating the various canal command areas from the upstream end of the system downwards. The results show that the productivity of water tends to a constant value at a spatial scale of 6 million ha and higher. At that scale, water diversion and water depletion are equal, which implies that groundwater systems, to a large extent, regulate losses and reuse of water resources. The Indus basin is an example of substantial groundwater recycling and this needs to be taken into account in analytical frameworks of water productivity.