Analysis About Reservoir's Siltation In Shanxi Province And The Variation Of Its Storage Capacity

Because of the river valley soil erosion and the river has great sand capacity, and bad management etc, it results in the problem of reservoir sediment is very seriously. Based on the calculating on the surveyed storage loss speed, some flood detaining storage of many medium-and-small scaled reservoirs would be silted, which cause a series of problem, it mainly include:(1) the flood-prevention capability keeping decreasing. (2) The decreasing effective storage reduces the reservoir's capability of impounding water and the benefit of water supply. (3) Heavy sedimentation will be induced at the end of the backwater, and the sedimentation will develop to the upper-current gradually which leads to the upper-stream bed rising in a rather length and the navigable condition will deteriorate. (4) The underground water in the upper two sides banks can not be drained easily which leads to inundating and saline soil in lower lying land. (5) The reservoir will cause sedimentation at the lower reach bed, which leads to disadvantage influence on diversion buildings for water supply and irrigation. (6) The sediment also influences and conveyances pollution.According to the current research and practical experiences, the ameliorative measure are put forward in this paper: (1) Sediment monitoring and hydrology forecasting system can do a great help to sediment discharging. And the system must be established basing on the characteristic of the watershed, the rainfall process, the reach shape and the regular of sediment transportation, and the reservoir's situation. (2) It is urgent to modify the operation modes according to the condition of water-flow and sediment situation. It is also necessary to train the management staff of the reservoirs. (3) It is a best way to construct dammed-up reservoirs on the nearly upper streams. Because the upper reservoir can not only decrease the sedimentation of the lower reservoir and its fertile beach face can be farmed in non-flood season or when the reservoir is empty which will benefit the local farmers a lot. (4) Water and soil conservancy is the ultimate way to prevent the reservoir sedimentation. The practical ways are constructing warping land dam, returning lands for farming and grassing.