Design and Operation of Sustainable Reservoirs, a New Approach

A reservoir is an artificial lake which begins to fill with sediment as soon as it is commissioned causing a gradual loss of storage capacity. Today, most dams of substantial size are engineered to have a practically unlimited life so far as the structure itself is concerned, provided it is given adequate maintenance. Modern geotechnics can be applied to dam site exploration and engineering skill in design reduces the risk of almost all types of structural and foundation failure. Present day knowledge of probable maximum precipitation (PMP) and probable maximum flood (PMF) has led to spillway design that leaves only a very small chance of failure from floods. Despite the above achievements, the reservoir sedimentation received less attention in study, design and operation stages. According to ICOLD sedimentation committee (March, 2009), the total storage capacity of the world reservoirs is about 7000 billion m3, of which 2000 billion m3 is the volume of deposited sediment, corresponding to an annual loss of .8%. It means that the half-life of the world s reservoirs in average is about 60 years, 2/3 of which is already past. Therefor it is very clear that the present rate of reservoir sedimentation along with such a huge amount of accumulated sediment will impose a very costly liability upon the next generation, hence a better understanding is urgently needed. The author believes that the present generation particularly those who are in the position of making key decisions must answer the following question. What shall the future dam operators do while facing with the abandoned reservoirs full of sediment? This paper describes a new approach of design and operation of dam reservoirs based on sustainable development principles, the reservoirs with almost unlimited life-cycles. The philosophy of the new approach is described as below. 1. A river system is a live element of the nature because it moves, it digs, it deposits, it carries, and it changes the environment to stabilize itself. 2. All the live elements of the nature need a part of their power to survive their live. As a reservoir is a part of a river system, thus the above philosophy should be fulfilled in its design and operation. Steps taken in the new approach have been elaborated using 15 years field experiences on de-siltation operations carried out at Sefidrud Reservoir, Iran.