9.1 Hydrological effects
A hydroelectric scheme is not basically a consumer of water, but the installation does ‘rearrange’ the resource. Diverting a river into a canal, or a mountain stream into a pipe, may not greatly change the total flow, but it can have a marked effect on the environment. Furthermore, evaporation from the exposed surface of a large reservoir may appreciably reduce the available water supply.
Any structure on the scale of a major hydroelectric dam will affect its environment in many ways in addition to the hydrological changes. The construction process itself can cause widespread disturbance, and the effect on a fragile eco-system can be long-lasting. In the longer term, a large reservoir is bound to bring other significant environmental changes. Whether these are seen as catastrophic, beneficial or neutral will depend on the geographical and biological situation – and on the points of view and interests of those concerned.
More generally the issue of water rights is one of major international significance and, flowing water having little respect for international boundaries, the source of numerous international legal disputes and arguably a few wars. Several of the disputes, across all continents, have concerned hydroelectricity schemes including, in recent years, the Brahmaputra River crossing from China into India, the ‘Grand Ethiopian Renaissance Dam’ on the Nile, and the Ilisu Dam on the Tigris River in Turkey (Johnson, 2014).
With increased demand for fresh water due both to an increasing population and improved living standards the sustainable management of water resources, including their use in power generation, is a priority.
Furthermore climate change is altering hydrological systems in many regions as changing precipitation patterns, snowmelt and melting glaciers affect the quality and quantity of water resources in many regions around the globe (IPCC, 2014).