Modeling and Investigation of Annual Nitrate Pollution Trend of Tajan River with QUAL2Kw and HEC-RAS

Document Type : Research Paper


1 Department of Water Engineering, Faculty of Agriculture, Shahrekord University, Shahrekord, Iran

2 Member of the academic staff of the Water Engineering Department, Faculty of Agriculture, Shahrekord University, Shahrekord, Iran


Continuous evaluation of water pollution is an important and vital issue in the optimal management of water areas. In this research, the trend of nitrate pollution along about 50 km of Tajan river, the distance between Rigcheshmeh hydrometric station and Kordkheyl station, during the year 2017, was investigated. To realize this, first the hydraulic conditions governing the flow were determined using the HEC-RAS model and entered into the QUAL2Kw model. After recalibration and validation of the model, time-spatial changes of nitrate pollutant in the river course were investigated. The results showed that the input load from non-point pollution sources and in the season of cultivation to the river is higher, which causes the nitrate load to exceed the maximum allowed. The trend of increasing nitrate concentration in the non-cultivation season is about 19%, and now, due to the excessive use of fertilizer in the cultivation season, this figure reaches about 50% with an increase of about 2.8 times. The concentration of nitrates in the growing season, in the final part and the continuation of the flow path, has reached about 47 milligrams per liter, which is close to the permissible level of 50 mg/lit for drinking use and much more than 30 mg/lit for agricultural use, which limits water harvesting for the relevant uses with It faces limitations. Therefore, it is necessary to determine a framework for reducing and controlling the nitrate load, focusing on non-point polluting sources in the management policies of the water ecosystem of the Tajan River.


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