جستجوی مقالات مرتبط با کلیدواژه « sufi-2 » در نشریات گروه « آبخیزداری، بیابان، محیط زیست، مرتع »

The spatial quality of the Digital Elevation Model (DEM) has a great effect on the Soil and Water Assessment Tool (SWAT) semi-distributed model. The purpose of this study was to evaluate the effect of spatial accuracy of three DEMs with spatial resolutions of 10, 50 and 200 m on the results of daily discharge simulation in the Arazkuseh subwatershed located in Gorganroud watershed, Golestan province, Iran. To do this, after-mentioned DEMs was obtained.  First, the model was run using a DEM with a spatial resolution of 10 m and climate data from 1998 to 2013. So that 1998 to 2000 were used to warm-up the model, 2001 to 2009 to calibrate and 2010 to 2013 to validate the model. In the validation period, the results of coefficient of determination ranged from 0.40 to 0.60 and Nash-Sutcliffe efficiency criteria ranged from 0.37 to 0.58. Both criteria had a decreasing value in the validation phase compared to the calibration phase. The PBIAS criteria was negative for DEMs with 10 and 50 m spatial resolution, respectively which indicates overestimation, and positive value ​​for DEM with 200 m spatial resolution, which represents the overestimation of the model. The results showed that the spatial resolution of 50m is the best spatial resolutions to simulate the discharge on a daily time scale for Arazkuseh watershed.

This study focuses on simulation and management the various hydrological responses to climatic changes. The semi-distributed hydrologic model SWAT (soil and water assessment tool) was used to evaluate runoff and water balance due to climate changes in Siminehroud and Zarrinehroud watersheds. The simulation period was selected between 1990 and 2014. The assessment results in the calibration and validation periods using the NS and R2 obtained 0.75, on average. Using statistical multisite downscaling of LARS-WG climatic models MIROC-ESM-CHEM، GFDL-ESM2M and NorESM1-M the future climatic condition entered to the model using two optimistic RCP2.6 and pessimistic RCP8.5 scenarios. The largest changes in runoff in the upcoming period, May, reduced by 2.4 m3 s-1 and in April, increased by 1.49 m3 s-1 in the optimistic scenario. In RCP8.5 pessimistic scenario in May and June, also the highest runoff was observed. The rate of actual monthly evaporation will increase in the optimistic scenario up to 3 mm and in the pessimistic scenario up to 8 mm increase will have a negative impact on the available water resources in the watershed. With estimation the climate changes and its effect on the stream flow discharge is possible performing a suitable management in Siminehroud and Zarrinehroud watersheds.

In water efficiency studies, the values of runoff, evapotranspiration and range production are the main variables. Rangelands of Golestan province, Iran, have a high potential of run-off due to the geographical location, climate, and destruction of these resources as well as drastic land use change from forests and rangelands to agricultural lands. Therefore, in the present study, in order to determine the best management of rangelands, we developed a rangeland improvement model using the Soil and Water Assessment Tool (SWAT) in the Gorganrud Watershed, Golestan Iran. Calibration and validation of model was performed using Sequential Uncertainty Fitting Program (SUFI-2) in the eco-hydrological model SWAT. For this purpose, the SWAT was calibrated and validated for a 31-year period of discharge and 5-year period of range production and then the model was executed for different scenarios of rangeland management. The results showed that the model performance was satisfactory for predicting discharge. The values of Nash-Sutcliffe coefficient were calculated to be 0.72, 0.71 and 0.64 in calibration period and 0.59, 0.48 and 0.53 in validation period for Basirabad, Tilabad and Haji Ghoshan stations, respectively. As well, four range improvement scenarios (mechanical, biological, biomechanical and livestock grazing management) were defined in this study. On average, by applying mechanical, biological, biomechanical, and grazing management scenarios evapotranspiration was increased to 2.3%, 12.8%, 15.5% and 2.8%, respectively, in comparison with actual evapotranspiration. According to the obtained results, the biomechanical scenario was identified as the best one in increasing evapotranspiration in poor and moderate rangelands.