Dams and reservoirs in karst? Keep away or accept the challenges

Abstract

The distribution and flow of groundwater in karstified rocks can be extremely complex and not readily predictable, a far from friendly environment for constructing dams and reservoirs. There have been many expensive failures such as unacceptable leakage rates at and around dams, and/or reservoirs that could not be filled to the design levels. This is never the fault of site geology but always of human mistakes due to inadequate investigation programmes and/or erroneous interpretation of the karst processes at work. Remedial works are expensive, time-consuming and frequently do not justify the money invested. As a result, those undertaking engineering works in karst terrains may approach with two fears—of the exceptional risk and/or of a failure. The key question, so often, is whether to build the dam in karstified rocks or keep away from such a risky environment. However, construction of water storage reservoirs is essential in many karst regions for socio-economic development. The challenge must be accepted. Based on much field experience, the best practices for selection of adequate dam and reservoir sites are defined and illustrated with specific examples from many different climatic, topographic, lithologic and hydrogeologic settings in Europe and Asia. This work emphasises that the amount of certainty or uncertainty in the crucial parameters—geological structure, groundwater regime, intensity and depth of karstification—should be recognized.