To assess the impacts of climate change on runoff in Golestan Province, Iran

Climate is a complex environment that is evolving primarily as the greenhouse gases increase. Due to the importance of climate change and the impact it can have on water resources, evaluation of the effect of climate change on water sources has been considered in various watersheds on the planet in recent years. The aim of this research is to assess the impacts of climate change on runoff in Golestan Province. This research consists of two parts of climate and hydrology. In the climate change part, daily data of the minimum temperature, maximum temperature, precipitation, and sunny hours of the synoptic station of the Hashemabad of Gorgan and the rain gauge station of the Naharkhoran during the period of 1985–2013 were simulated using LARS-WG6 statistical model. After verifying the model efficiency in simulating the mentioned meteorological parameters in the Ziarat watershed, the data from three Representative Concentration Pathways (RCP) scenarios (RCP2.6, RCP4.5 and RCP8.5) from HadGEM2-ES model in two periods of 2041–2060 and 2061–2080 were downscaled by the use of LARS-WG6 model to evaluate the impact of climate change on runoff. In the hydrological part, rainfall and runoff were simulated using the IHACRES hydrological model. After calibration in the 1990–1992 period and validation in 2001, the temperature and rainfall data extracted from the LARS-WG6 model were entered in the IHACRES model and runoff changes caused by climate change were calculated in future period relative to the base period. Based on the estimation of LARS-WG6 model for the future scenarios, the results showed that the minimum and maximum temperature of the Ziarat watershed will increase to the amounts of 1.81 to 4.56 °C. The amount of rainfall also varies from 4.79to 16.38 mm in comparison with the base period. Also, the amount of runoff under three scenarios in three periods has changed from −0.373 to 0.308 m3/s in comparison with the base period. These results can be considered in the long-term development programs in water resources sector.