Effect of Land Use on Phosphorous, Nitrogen, Dissolved Solids, and Suspended Solids Concentrations and its Presentation in GIS (Case Study: Zayandehroud Basin)

Among most important pollutants that cause water pollution, are nitrogen and phosphorus in agricultural runoff acting as non-point source pollution. In this study, L-THIA model is used to calculate the amount of total phosphorus, total nitrogen, nitrate-nitrite, total soluble solids and suspended solids. SPSS software is used to evaluate the relation of these parameters to land use in the Zayanderoud river basin. Five subbasins with the highest land use diversity were selected and the boundary of each sub-basin and different land use coverage were determined with ArcView HEC-Geo-HMS extension. Then in each sub-basin 1 station was selected and the concentrations of phosphorus, total nitrogen, total soluble solids and suspended solids were measured from March 2015 to March 2016. Statistical analysis and Pearson correlation coefficient indicated that there is a significant relationship between all pollutants and land uses, except for dissolved phosphorus. Besides there was a significant relationship between residential area and bare lands with all pollutants, except for dissolved solids and nitrate-nitrite. Dissolved solids were meaningfully related to forest and grasslands. Considering accumulation zones of phosphorus and nitrogen in the watershed and identifying areas with high concentrations of these materials, management actions should be used to reduce the amount of nitrogen and phosphorus and ultimately decrease the amount of pollution in the watershed.