The Effect Of Land Use Changes and Drought On Runoff in the Central Zagros Basin (Case study: Basin Tuyserkan)

Land use change in watershed management one of the most important hydrological factors surface runoff change and water management practices. the purpose of this investigation, Impact of Land Use and drought on runoff of  Tuyserkan watershed in Hamedan  In central zagros In the three time periods of 1991, 2003 and 2015 (25 years) using hydrological modeling is the rainfall-runoff relationship (IHACRES). First to prepare and survey the land use map from digital data TM and ETM + sensors and Arc Gis 9,3 software and also to calculate drought From SPI index with DIP model and the annual time period was used as a conventional hydrological cycle. The Results of 3 and 12-month drought indices the 25 year period shows most years On three Classification mild humidity, mild drought, and severe drought And has severe hydrological fluctuations.The results show that the largest land use change over the 25 years, In the areas of natural resources, especially in rangelands affected by drought and the decline of these lands along with drought fluctuations over time, the volume of runoff has increased.The Results of calibration of simulation runoff in rainfall and runoff model,  Indicates acceptable model performance and Investigation of basin hydrographs in three periods of 1991, 2003 and 2015 (25 years(  sdhows the runoff in the Tuyserkan basin has increasing trend, due to the not so noticeable drought, Significant land use change and increased rainfall in some years. Therefore, it is suggested,­ In order to manage water and soil resources, prepare a comprehensive plan to control land use change and land use in the watershed.