|Using Water Efficiently: Technological Options (WB, 1993, 61 p.)|
There is evidence that a worldwide shift in water resources allocation from agriculture to the urban sector is taking place, especially in developing countries. However, agricultural water use will continue to dominate in the foreseeable future. Major water savings are most likely to come from improving efficiencies in agriculture. Consequently, the Bank's water policy should, in dealing with water use efficiency issues, be focused on these aspects.
Technologically, there is great potential to improve water use efficiency in both the agriculture and urban sectors. Despite demonstrated success in water saving and favorable experience in many developing countries, advanced technologies, such as sprinkler and drip systems, are applied to less than 3 percent of the world's irrigated lands.
A focus on the technological dimension of water use leads to the following conclusions:
· At the basin level, investment decisions need to be based on more comprehensive views of basin water use when considering whether a certain level of local efficiency --for example, conveyance and distribution, field, or overall project -- is appropriate or should be increased.
· In areas, where there is little return flow or little recharge to be reused by downstream users, increasing local WUE through technological applications and managerial improvements is recommended. However, consideration should be given to the environmental dimension of the decision on issues such as preservation of aquatic life and wetlands in coastal deltas and estuary ecosystems.
· In areas, where there is potential for the reuse of seepage water or runoff losses elsewhere in the basin, especially where return flows are used repeatedly downstream, the technological solutions and investments in the upstream areas to improve localized water use efficiency, thereby making more water available to upstream users, has to be traded off against lower water supplies to downstream users. Such investments should be evaluated from the viewpoint of water conservation in the whole basin. Improving low efficiency upstream to release more fresh water to downstream areas has a favorable environmental impact on water quality. It also generates economic benefits/savings in areas where costs for water pumping are high.
Before adopting technical options for improving WUE, the economic, technical, social and environmental objectives need to be specified clearly. It is important, at this stage, to understand the hydrogeological and hydrological linkages among the different project areas of a basin. Water conservation projects should be appraised considering the impact of projects on the water balance of river basins, based on adequate hydrological information. Efficiency levels and technologies should be selected to meet the specified objectives to avoid uneconomic investments, and to achieve sustainable and successful water development.
Technological decisions need to be integrated closely with evaluations of economic efficiencies. Water conservation should be viewed in a cross-sectoral rather than sectoral context. For instance, the premium on water saving in irrigation water should be evaluated not merely on the basis of the productivity of saved water in agriculture. Increases in crop production are only the first order of benefits to be evaluated. The contribution to additional industrial growth and the development of other water dependent activities that can be generated, particularly in areas where further development is hampered by shortage of water, needs to be incorporated into such measurements.
The Bank should promote policies that accelerate the transition from water-consuming to water saving economies. These policies should lead to the strengthening of management approaches to optimize overall water use, considering the contribution of water to the productivity in the various sectors, and the promotion of water reuse as an integral part of water resource development projects. In view of the potential impact of water reuse on health and environment, the reinforcement of monitoring and quality control should be part of design of water resources reuse programs. To evaluate Bank financed projects, technological measures to increase water use efficiency at the basin level should be determined based on the overall water use in the whole basin, and at the local level should be selected based on costs, social and environmental consequences.