RESERVOIRS AND DRINKING-WATER SUPPLY - A GLOBAL PERSPECTIVE

The history of water-storage management and drinking-water reservoirs is introduced briefly. Examples illustrate the development from the local water supply and flood-control schemes of antiquity, to the highly sophisticated inter-regional water-supply systems of our own times. Inter-regional reservoir-systems that pipe water over great distances can compensate for insufficient or irregular precipitation, particularly in the semi-arid regions of the world. In regions relying on rivers for both drinking-water supply and sewage disposal, impounding reservoirs provide an alternative water resource at times of heavy river pollution. The impoundment of running waters causes profound limnological changes and affects water quality in many different ways. Water-retention time and reservoir morphology are very important factors that determine the limnological characteristics of reservoirs. Retention time has a strong bearing on the tolerable phosphorus concentration and the associated bioproduction. The quality of the raw water (especially the nutrient load) is a critical factor with regard to the trophic state and the self-purification of reservoirs. After a discussion of various management approaches for the protection and operation of drinking-water reservoirs it is concluded that the fundamental limnological requirements of drinking-water reservoirs are basically reflecting the concept of a multiple-barrier system.