%0 Journal Article %T Investigating the effects of best management practices on the reduction of point and non-point source pollution of water using SWAT model (Case Study: Seimareh River) %J Iranian Journal of Soil and Water Research %I University of Tehran %Z 2008-479X %A Noori, Zahra %A Salajegheh, Ali %A Malekian, Arash %A Moghadamnia, Alireza %D 2018 %\ 01/21/2018 %V 48 %N 5 %P 995-1006 %! Investigating the effects of best management practices on the reduction of point and non-point source pollution of water using SWAT model (Case Study: Seimareh River) %K surface water quality %K Point Source (PSP) and Non-point Source Pollution (NPSP) %K SWAT Model %K Best Management Practices (BMPs) %K Seimareh River Watershed %R 10.22059/ijswr.2018.225610.667617 %X Surface water quality has a far-reaching impact on the human health and aquatic ecosystems. The sources of surface water pollutions include Point Source (PSP) and Non-Point Source Pollution (NPSP). The action of Identifying the point source and non-point source pollutions is critical to evaluate surface water quality and major pollutant sources in a watershed. In this study, Soil and Water Assessment Tool (SWAT) was used to investigate the influence of PS and NPS Pollution on the water quality. The model was calibrated for the period 2000-2009, and then it was validated for the period of 2010 to 2011. The values of Nash-Sutcliffe efficiency (ENS) and R2 for simulations of flow and nutrient loads range from 0.84 to 0.96 for calibration period, while they vary from 0.69 to 0.85 for the validation period used for flow simulation. The statistical results revealed that the SWAT model simulated the monthly flow and nutrient loads satisfactorily in Seimareh watershed. Also, SWAT model was used to identify the critical source areas (CSAs) of sediment, TN and TP at the watershed level. SWAT model identifiedof 9 sub-the watershed (33% of total watershed area) as CSAs for TN and TP.  The sub-watersheds 1, 6, 10, 17, 21,22, 25, 26 and 29 were identified as CSAs of TN and TP while most of these sub-watersheds were also identified as sediment CSAs. Then, the model was also used to simulate the impact of Best Management Practices (BMPs) at controlling nutrient losses. Major BMPs implemented were reducing chemical fertilizer application, and building a filter strip along the river bank. The result of WQI demonstrates that water quality at the upstream is generally better than the downstream with higher level of nutrient loads. Also, the seasonal variations  WQI clearly indicates the summer and autumn season as the critical time period for nutrient loads within the watershed. The result showed that the BMP scenario reduced the pollutant losses compared to the baseline condition, and the greatest reduction in the nutrient losses was observed in the filter strip located along the river with percentage reductions of 68%, 36% and 39% for sediment, TN and TP, respectively. Overall, this study helps our understanding of the status of water quality and the role of the best management practices (BMP) options to improve water quality. %U https://ijswr.ut.ac.ir/article_64754_847102e479cafc0a03cf50056aea78d2.pdf