The Role of Reservoir Dams in Flood Control at Large Watersheds

摘要

Dam construction in upstream of each watershed usually change the hydrologic characteristics of that basin and can decrease the maximum flood discharge. Atrak watershed is one of the largest basins in the north east of Iran, with a catchments area of 17687 Km2. During last 8 years 5 large and small dams are constructed in this watershed.In this research study area is divided in to 31 sub basins and is modeled in WMS hydrologic software. Muskingum method is used for flood routing in channels and the relation between the outflow and water level in reservoirs is considered for Flood routing in reservoirs. By the use of rainfall data at some meteorology gage stations during some special storm events, and related flood hydrographs which is measured at the outlet gage station, Curve Number is calibrated. This calibration belongs at the time when no dams were made in the basin.With provided hydrologic model, the effect of each dam in the upstream of river, on decreasing maximum flood discharge and formation of hydrograph at the outlet is investigated.