Environmental impacts of reservoirs

Abstract

The construction of reservoirs is one of the most important practices for the development and management of water resources. Many large reservoirs were built without a thorough or systematic evaluation of the long-term environmental, social, and economic interactions of different alternatives. Up to the last quarter of the twentieth century, those responsible for the construction of dams and creation of reservoirs — entrepreneurs, decision makers, engineers, investors — were praised for the acknowledged benefits of their works: Water supply, irrigated agriculture, flood control, improved navigation and firm hydroelectric generation (considered clean and unequivocally renewable energy). However, on the other hand, alarmist, especially environmental groups and organizations, have been exaggeratedly stating that infrastructure works, in general, and dams and reservoirs, in particular, cause serious and intolerable environmental impacts. Reservoir construction leads to a number of environmental issues, both during building and following completion. The physical, chemical character and water quality of rivers draining into lakes and reservoirs are governed in part by the velocity and the volume of river water. In these last decades of industrialization and rapid population increase, human intervention on the balance of nature has never been so various and so extensive as it is today. This chapter reviews a large range of potential impacts linked to the exploitation of reservoirs and dams, such as: (1) Climate-changing greenhouse gases emissions; (2) Changes in the Temperature Regime (3) Reservoir sedimentation; (4) Water pollution; (5) Destruction of Eco-systems, and (6) Planning and reservoir management.