Analysis of trend and heterogeneity of hydroclimatic variables in Tajen watershed

In Iran, due to warming and severe precipitation variation along with development in recent decades, more attention should be paid to comprehend the role of climatic factors in water resources. Therefore, this study aims to analyze the trend and heterogeneity of the climatic variables as well as their impact on hydrological processes.

Material and Methodology :

The stations with long-term data were analyzed for trend analysis (Mann-Kendall tests) and homogeneity (Pettitt test) of climatic variables in a 30-year statistical period (1984-2014). The impacts of climatic variables on the basin's runoff were investigated using the Soil and Water Assessment Tool (SWAT) for two climatic time periods (1984-2001 and 2001-2014).

The homogeneity investigation in the stations demonstrated that only in Soleiman Tangeh Station, the year 1998 was determined as the turning point. This case was not observed in other stations. Regarding the investigation of temperature associated with Gharakhil station, the turning point was obtained in 1997 and the trend was increasing and meaningful. The results of the coefficient of determination and Nash-Sutcliffe achieved from the calibration and validation of the SWAT were quite satisfactory.

In general, climate change over the past three decades has led to decline in the runoff of the basin, which may be partly due to the increased evapotranspiration as a result of increased temperature or reduced precipitation in most months. The present study attempts to indicate the significance of climate change and its consequences in the water resource management of the Tajan basin.