Tarbiat Modares University (TMU) ECOPERSIA 2322-2700 4 2 2016 06 01 Using SWAT Model to Determine Runoff, Sediment Yield and Nitrate Loss in Gorganrood Watershed, Iran 1359 1377 17172 EN Samane Mahzari Former M.Sc Student, Department of Soil Science, Gorgan University of Agricultural Sciences and Natural Resources. Gorgan, Iran Farshad Kiani Assistant Professor, Department of Soil Science, Gorgan University of Agricultural Sciences and Natural Resources. Gorgan, Iran Mojgansadat Azimi Assistant Professor, Departmentof Range and Watershed Management, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran Farhad Khormali Professor, Department of Soil Science, Gorgan University of Agricultural Sciences and Natural Resources. Gorgan, Iran Journal Article The adequacy of the SWAT model in the estimation of runoff, sediment yield and nitrate loss in the Gorganrood watershed was tested, using the existing spatial database as the primary data. The model was then executed for a 31-years’ time period. In combination with the SWAT model, the Sequential Uncertainty Fitting Program (SWAT-CUP and SUFI-2) was added used to calibrate and validate a hydrologic model of the watershed. The obtained values at 14 stations were between 0.48 to 0.83 for NS and 0.58 to 0.90 for R², respectively. The results showed that nitrate loss was higher in cultivated lands, and in the loess deposits. The maximum amounts of runoff and sediment yield were largely produced in steep areas of the watershed, where dry farming was practiced. In general, the results showed that SWAT could be a proper tool for simulating runoff, sediment yield and nitrate loss into the river. https://ecopersia.modares.ac.ir/article_17172_51c9d0385c088de752dfb41cfa835a37.pdf