Modelling water and nitrate budget in left bank irrigation of lower Seyhan Plain

This study represents an application of the Soil and Water Assessment Tool (SWAT) to an agricultural catchment, called Akarsu irrigation district, in the Lower Seyhan Plain located at the Eastern Mediterranean region of Turkey. The catchment covers a drainage area of 9 495 ha. The main objective of this study was to introduce SWAT model and calibrate the model against daily drainage discharge and nitrate (NO3) concentrations derived from the field stations. The modelling period was covering the hydrological years of 2009 and 2010. Major input variables to run the model were climate data, soil type, land use, management practices and topography at watershed scale. Sequential Uncertainty Fitting (SUFI-2) linked to SWAT was utilized for calibration of the model. SUFI-2 is associated with SWAT in the Calibration Uncertainty Program called SWAT-CUP. Calibrations were conducted using the SWAT-CUP program and SUFI-2 algorithm. Calibration based on the Nash-Sutcliffe coefficient of efficiency (E) and R2 was done through using daily data. Interpretation of model calibration results led us to conclude that the simulated SWAT drainage flows and their corresponding nitrate loads were reasonably accurate for the Akarsu irrigation district.