Investigate the Estimation of Regional Annual Discharge Relations with Different Return periods at Sefidrood Dam Basin

One of the requests of good management of water resources is to understand the hydrological relations specially estimation of annual discharge with different return periods. In this research to take different annual discharge estimation models with different return periods at sub-basins of Sefidrood dam basin, the first gathered or measured data and information about climatology, hydrology, geology, ecology and morphometry of sub-basins. Then the gathered data reviewed and by correlation method the loose data reproduced and by Run test and Double mass methods investigated the homogeneity and verification of data. For catching the hydrological homogeneous sub-basins based on physiographic specifications and annual rainfall the hierarchical analysis was done and by canonical diagnostic function the borders of clusters were clarified. After the suitability of conventional probability functions for every hydrometry station was tested based on Mean Square Error (MSE) index and was selected the suitable probability function to any of them. The annual discharge of every hydrometry stations was estimated with return periods of 2 to 200 years. Then Principle Component Analysis (PCA) was done on physiographic and climatology parameters and variables of area and mean height of sub-basins was recognized as effective factors about average annual discharge. Multivariate regression equations were created among mentioned independent selected variables and average annual discharge as dependent variable and were tested by other observed hydrometry data and finally the easiest and compatible mathematical model was selected. Then mean ratio of annual discharges with different return periods at every hydrometry station over average annual discharge of that station was calculated and suitable mathematical models of relations between these ratios with different return periods was produced. Finally the mathematical equation of estimation of annual discharge of sub-basins with different return periods and sub-basins' area was introduced all over the sefidrood basin. Key words: annual discharge, mathematical model, sefidrood