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This study aims to develop a hydrologic model for the Ladik Lake Basin in Turkey using the Soil and Water Assessment Tool (SWAT). Ladik Lake is located in the Yesilirmak River Basin in Samsun, Turkey and covers an area of about 10 km2. The lake supplies irrigation water to 88 km2 command area. In this study, the water volumes in the Ladik Lake were simulated with SWAT. SWAT is a semi-distributed hydrologic model that can be used for simulating hydrology, water quality, crop development, irrigation operations. In this study, SWAT model was established based on digital elevation model, land use, soils, and slope data and meteorological data. Irrigation withdrawals were simulated using auto irrigation tool, which determines the timing and amount of irrigation according to the plant water stress factor. SUFI-2 algorithm was used for calibration and validation of the model for lake volumes. The model was run at the monthly time step over the period 2010-2017. The Nash-Sutcliffe Efficiency (NSE) between the measured and simulated water volumes was calculated as 0.66 and the coefficient of determination (R2) was calculated as 0.67 for the calibration period (2010-2015). For the validation period (2015-2017), NSE was 0.58 and R2 was 0.60. These results showed that SWAT can successfully simulate the hydrological processes in the Ladik Lake basin. [ABSTRACT FROM AUTHOR]

This study aims to determine climate change impacts at Ladik Lake in Turkey using the Soil and Water Assessment Tool (SWAT). Ladik Lake is a natural lake and an ecologically important site located in the Yesilirmak River Basin in Turkey. In recent years, water level changes in the lake raised concerns regarding its future hydrologic and ecological characteristics. In this study, we used a basin-scale hydrological model, developed using SWAT, to simulate the sensitivity of Ladik Lake to climatic changes. RCP4.5 and RCP8.5 scenarios developed by MPI-ESM-MR, HadGEM2-ES, and GFDL-ESM2M Global Circulation Models outputs were used for representing future climatic conditions. These models were previously downscaled for Turkey by State Meteorology Service. Maximum and minimum temperature and precipitation projection data were added to the model for the 2021-2098 period. Annual reservoir volume data of 78 years from 2021 to 2098 period has been processed using Mann-Kendall Trend Analysis for the determination of trend (Z value) and slope (Q value) magnitude. The detected trends for the GFDL-ESM2M model were positive (upward) for RCP4.5 and negative (downward) for RCP8.5. While the rate of change in the RCP4.5 was 233 m3/year, this value was -77885 m3/year for the RCP8.5 scenario. The trends determined for the HadGEM2-ES model were negative for both the RCP4.5 and RCP8.5 scenarios. The decrease in RCP4.5 was -1111 m3/year, and the decrease in RCP8.5 was -1786 m3/year. For the MPI-ESMMR model, the detected trends were negative for both the RCP4.5 and RCP8.5 scenarios. The decrease in RCP4.5 was found to be -126620 m3/year, while the decrease in RCP8.5 was -273806 m3/year. Ladik Lake volume decreased in most of the models and scenarios, except for the GFDL-ESM2M model RCP4.5 scenario. These results suggest that Ladik Lake's water volumes are very sensitive to future climatic changes. [ABSTRACT FROM AUTHOR]