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The Indus basin of Pakistan occupies about 16 million ha (Mha) of land. The Indus River and its tributaries are the primary sources of surface water. An estimated 122 km3 of surface water is diverted annually through an extensive canal system to irrigate this land. These surface water supplies are insufficient to meet the crop water requirements for the intensive cropping system practiced in the Indus basin. The shortfall in surface water is met by exploiting groundwater. Currently, about 62 km3 of groundwater is pumped annually by 1.36 million private and public tube wells. About 1.0 million tubewells are working only in the Punjab province. Small private tubewells account for about 80% of the pumped volume. Inadequate water allocation along the irrigation canals allows excessive water use by head-end farmers, resulting in waterlogging. In contrast, the less productive use of erratic supplies by tail-end farmers often results in soil salinity. The major issues faced by irrigated agriculture in Pakistan are low crop yields and water use efficiency, increasing soil salinization, water quality deterioration, and inefficient drainage effluent disposal. Currently, 4.5 Mha (about 30% of the total irrigated area) suffers from adverse salinity levels. Critical governance issues include inequitable water distribution, minimizing the extent to which salt is mobilized, controlling excessive groundwater pumping, and immediate repair and maintenance of the infrastructure. This paper suggests several options to improve governance, water and salt management to support sustainable irrigated agriculture in Pakistan. In saline groundwater areas, the rotational priorities should be reorganized to match the delivery schedules as closely as possible to crop demand, while emphasizing the reliability of irrigation schedules. Wherever possible, public tubewells should pump fresh groundwater into distributaries to increase water availability at the tail ends. Any substantial reform to make water delivery more flexible and responsive would require an amendment to the existing law and reconfiguration of the entire infrastructure, including thousands of kilometers of channels and almost 60,000 outlets to farmer groups. Within the existing political economy of Pakistan, changing the current water allocation and distribution laws without modernizing the infrastructure would be complicated. A realistic reform program should prioritize interventions that do not require amendment of the Acts or reconstruction of the entire system and are relatively inexpensive. If successful, such interventions may provide the basis for further, more substantial reforms. The present rotational water supply system should continue, with investments focusing on lining channels to ensure equitable water distribution and reduce waterlogging at the head ends. Besides that, the reuse of drainage water should be encouraged to minimize disposal volumes. The timely availability of farm inputs can improve individual farmers’ productivity. Farmers will need to have access to new information on improved irrigation management and soil reclamation approaches. Simultaneously, the government should focus more on the management of drainage and salinity.

Farming accounts for approximately 70 percent of freshwater withdrawals worldwide, and it often constitutes the lowest value use of freshwater. Where water is scarce, advanced irrigation te...

The Hai Basin in China exemplifies problems that are observed in many arid environments: excessive water consumption, depletion of aquifers, and damage to eco-systems. Progressively since the 1970s water resources in Hai Basin have been over-exploited, primarily for irrigation, while the water requirements of other sectors have increased. Water tables are falling and outflows to the sea are sporadic and heavily polluted. Current consumption of water in the basin is estimated to exceed the renewable supply from rainfall by 6.25 × 109 m3 yr−1. Traditional approaches—improving irrigation efficiency through structural works and on-farm technologies such as drip and sprinkler—have failed to restore a balance. Researchers have investigated various on-farm techniques to reduce consumption, including mulching, zero tillage, deficit irrigation, revised cropping patterns, and improved cultivars. We project the results of such experiments for winter wheat (Triticum aestivum L.), maize (Zea mays L.), and cotton (Gossypium spp.) to basin scale to assess their potential in restoring sustainable water consumption. Widespread adoption of mulching, which is the most promising option for farmers, would reduce the over-consumption by 25% (1.6 × 109 m3 yr−1). If water quotas are introduced, forcing a reduction in consumption, current production could be maintained while saving 4.1 × 109 m3 yr−1. Ending the remaining over-consumption of 2.15 × 109 m3 yr−1 would require reducing grain production by 4–7.8 Mt yr−1.

As the demand for water resources continues to grow, the current “demand management” approach often fails to deliver the expected results in terms of reduced water consumption, release of water to other uses, or improved environmental conditions. Recognizing that evapotranspiration (ET) represents the dominant consumptive use of water in the hydrologic cycle, this paper describes an approach to basin-scale water resources management based on ET. The ET management approach comprises four stages: (i) a basin-scale water consumption balance; (ii) determination of a target ET consistent with sustainable water consumption; (iii) identification of water consumption tradeoffs, competition and feedback among different water sectors (agricultural, industrial, domestic, and socio-environmental); and (iv) basin-wide monitoring of sustainable water consumption. Continuous, basin-wide ET data obtained from the ETWatch models are combined with estimates of water consumption as a result of mechanical, chemical, and biological energy to assess the water consumption balance, and set targets. On this basis, water resource managers can identify opportunities to achieve sustainable, productive use of water resources by (i) reducing non-beneficial ET; (ii) converting non-beneficial ET to beneficial ET; and (iii) increasing the productivity of beneficial ET. Irrigated agriculture is usually the largest controllable contribution to ET in a basin, so meeting the target ET for agriculture is key. A water balance analysis for Hai Basin and the implementation of ET management in the Basin are presented to illustrate the ET management approach.

Virtual water and water footprints have gained recognition as indicators to guide action on issues related to water scarcity. I argue that water footprints are fundamentally different from carbon footprints, as local reductions in carbon emissions have global benefits, while global attempts to reduce water footprints will have neither necessary beneficial impacts in areas of local water scarcity, nor global impacts on atmospheric water content. In addition, water footprints have little or no meaning for purposes of setting policy regarding national water use or international trade. Furthermore, the calculation procedures adopted in most estimates of water footprints are flawed. Finally, I suggest that water footprints are incorrectly assessed on an absolute, rather than a relative basis. Water analysts are fortunate to have hydrology, a science with agreed procedures and standards, to use in describing the physical impacts of interventions in the hydrologic cycle. Generalised water footprints are neither accurate nor helpful indicators for gaining a better understanding of water resource management.

Irrigation is widely criticised as a profligate and wasteful user of water, especially in watershort areas. Improvements to irrigation management are proposed as a way of increasing agricultural production and reducing the demand for water. The terminology for this debate is often flawed, failing to clarify the actual disposition of water used in irrigation into evaporation, transpiration, and return flows that may, depending on local conditions, be recoverable. Once the various flows are properly identified, the existing literature suggests that the scope for saving consumptive use of water through advanced irrigation technologies is often limited. Further, the interactions between evaporation and transpiration, and transpiration and crop yield are, once reasonable levels of agricultural practices are in place, largely linear—so that increases in yield are directly and linearly correlated with increases in the consumption of water. Opportunities to improve the performance of irrigation systems undoubtedly exist, but are increasingly difficult to achieve, and rarely of the magnitude suggested in popular debate.

Water shortage shifts attention from the traditional concept of crop yield—production per unit of land—to the productivity of water—production per unit of water. Whether this parameter is best increased through responsive, sophisticated irrigation scheduling or through predetermined schedules, providing limited water, has been a contentious issue for some years. This paper brings together modelling studies from Pakistan that address this issue, as well as raising the question of whether deficit irrigation threatens sustainability through the build-up of salts in the soil profile. It is shown that under conditions of plentiful water, highest productivity is achieved when irrigation is precisely scheduled to meet crop needs. However, when water is short its productivity is substantially increased (by almost 50%) by deficit irrigation. No salt problem occurs as long as amount of water applied through irrigation is sufficient to meet 80% of the total crop evapotranspiration. Under limited water conditions, the productivity achieved is little affected by setting predetermined irrigation schedules, allowing the operating agency to concentrate on reliability of service. Finally, it is also shown that the salt build-up is independent of irrigation scheduling. Copyright © 2002 John Wiley & Sons, Ltd.