Modeling and Analyzing of Hydrological Regime Trend of Rivers (Case Study: Gorganrood River, Tamar Hydrometric Stations)

Precipitation, Temperature, runoff and floods are some of important parameters among climatic and hydrological parameters for forecasting and determination of their behavior in water resources management. In this research, for investigation of change in hydrological regime of Gorganrood River inTamar gaging station, the 44 years of hydrological data during 1969-2012 were used to model by GIS, ILWIS 2.1 and SMADA. Then, physical characteristics of watershed, temperature, precipitation, runoff trends, floods and discharge hydrograph were evaluated. The results show that the climate of the region will change to dried climate based on increase in temperature and reduction in precipitation, an increase in rainfall intensity and an increase in peak flow. On the other hand, the average monthly and annual discharge show the small increase which is in accordance to world climate change in Northern hemisphere and 30 degree latitude. Based on floods in Tamar gaging station, the biggest floods are in month of November, March, April and May during the period of 10 years with frequency of 14, 12, 12, and 12, respectively. Based on several recorded flood in Tamar gaging station, unit hydrograph of watershed was determined. Flood hydrographs with return period of 2 to 2000 years were determined based on time of concentration and time distribution pattern of rainfall.