Comparing the accuracy of salinity simulation using heavy metal and nitrogen cycle in model SWAT (Case study: Navrood basin)

In the past decades, human activities changes the quality of water resources significantly so that water resources have been contaminated or to be contaminated in the future. In this way, agriculture has more contribution to reduce water quality and increase consumption of surface water than other activities. Agricultural management in river’s watershed is one of the main approaches to improve the quality of water resources. Water quality simulation models in the basin scale, are the practical tools to simulate the impacts of various activities such as agriculture on the quality and quantity of water resources. In this study, the SWAT model to simulate the salinity load under two cycles, heavy metals and nitrogen in the catchment basin Navrood who represents the West Guilan, was used. The accuracy of the model to simulate the salinity in the two methods was compared. Calibration and validation of SWAT was conducted by data series of salinity and discharge during 2006-2013. To assessment the efficiency of model, two statistical indicators R2 and NS was calculated. The values of the indicators in simulating river flow were 0.82 and 0.58 respectively. In salinity simulation, these indicators were 0.30 and -0.71 under heavy metals cycle and 0.61 and 0.54 under nitrogen cycle, respectively. Therefore, the use of the nitrogen cycle in simulation of salinity load of Navrood basin is recommended.