One-third of the developing world will face severe water shortages in the twenty-first century even though large amounts of water will continue to annually flood out to sea from water-scarce regions. The problem is that the sporadic, spatial and temporal distribution of precipitation rarely coincides with demand. Whether the demand is for natural processes or human needs, the only way water supply can match demand is through storage. There are four major ways of storing water- in the soil profile, in underground aquifers, in small reservoirs, and in large reservoirs behind large dams. Storage in the soil profile is extremely important for crop production, but it is relatively short-term storage, often only sufficient for a period of days. In this paper, the authors concentrate on the three kinds of technologies that Summary store water for periods of months, in small reservoirs, or years, in aquifers and large reservoirs. These three technologies are compared from the hydrological, operational, and economic standpoints. Some of the environmental aspects of these options are also mentioned, but these aspects are very location specific and are not discussed in detail. The two principle conclusions of this analysis are: 1) aquifers and small and large reservoirs all serve an indispensable role in water storage, and each technology has strong comparative advantages under specific conditions of time and place; and 2) where it is possible to do so, substantial gains can be achieved by combining all three storage technologies in an integrated system.

Keller Andrew, Sakthivadivel R., Seckler David
Colombo IWMI - International Water Management Institute LK
Water in de Wereld - algemeen