Application of Continuous Rainfall-Runoff HMS-SMA Model in Estimating Runoff and Flood and Droughts Frequency of Neka BasinunderA2 Climate Scenario of HadCM3 Model

Evaluation of climate change and its possible consequences on hydrological processes in catchment will help to the challenges of water resources managers and decision makers in the future. One of the common tools for evaluating of this event is utilization of rainfall-runoff model to simulate the hydrological process. The aim of this study is to investigate effects of climate change on runoff and drought and flood events in the period 2040-2069 in Neka basin. In this study, a semi- distributed model for evaluating the impact of climate change was used on hydrological processes for Neka basin. in this approach, first the parameters of a continuous semi- distributed model SMA calibrated for the period 1981-2010, then in order to evaluate the effects of climate change on basin hydrology during 2040-2069 using Hadcm3-AR4 climate model data under A2 emissions for the region downscaled and downscaled data has presented to the SMA model and then changes of runoff were evaluated in future period. Comparison of observed and simulated climate parameters by climate models for the period 2040-2069 shows that the temperature in different months between 1.41 to 3.47 degrees Celsius warmer than the base period. Precipitation for the cold months has increased by about 23 percent to 25 percent decreases in the warm months. Also, the results of drought and flood frequency show that 7- day low flow decreased by 7% for the 200 years return period in 2040-2069 to 1981-2010 periods.