Investigation and analysis of factors affecting base flow in different climates of Iran

Watershed planning and management of water resources requires various data including base flow and its index. This parameter is influenced by Morphometric, geologic, hydrologic and climatologically factors and has always been one of the most important issues in hydrology. In this research, the Domarton method was used to map the climate of Iran with the use of temperature and precipitation data. Then, using daily stream flow data and after controlling for time series, base flow and related index, using two parameter the recursive digital filter were extracted in selected catchments of six climatic zones including; arid, semi-arid, humid and semi-humid and very wet and Mediterranean. Hydrological and climatically parameters of the basins measured and physiographic factors were extracted in the digital environment. To identify independent factors affecting base flow, factor analysis were down using 14 parameters in each climate zone and then effective factors were analyses. The results showed that more than 80 percent of the variance of parameters was explained by selected parameters. The intrinsic factors related to the penetration and retention of water in all climate zones are in the first importance order with the weight more than 45 percent. Flow duration curve indices in very humid, humid, semi-humid and semi-dry climatic zones respectively with 45, 53, 52, and 53 percent and in the dry and Mediterranean climate zones parameter of storage capacity, Respectively with 49 and 58 percent have the greatest influence over the base flow. The results showed that the weight of the factors affecting base flow, vary depending on the type of climate.