Determining the Spatial Trend of Water Quality Indices across Kan and Karaj River Basins

Due to the importance of water consumptions, this study aims to investigate the spatial trend of surface water quality along Kan and Karaj Rivers using three quality indices: NSFWQI, IRWQIsc and WQI.
The information of water quality parameters of 20 monitoring stations was collected to investigate water quality parameters along two mentioned rivers during 2012-2013, and water quality of two rivers were calculated using mentioned three quality indices. The parameters of TDS, FC, EC, nitrate and turbidity were used to measure the NSFWQI and IRWQIsc indices, and TDS, nitrate, and sulfate were used to calculate the WQI index. The measured parameters were compared with standards of drinking. The monitoring stations were grouped by cluster analysis and finally, the pattern of changes in water quality parameters and relevant quality indices were analyzed spatially using ArcGIS software.
The water quality of Kan and Karaj Rivers based on NSFWQI index were in the range of bad and average quality, respectively. According to IRWQISC index, water quality were in the range of very bad and relatively good, respectively and according to the WQI index water quality was in the range of good quality. The quality of upstream was acceptable for drinking and irrigation, on the basis of medium and good conditions of NSFWQI and IRWQISC, respectively. However, the downstream of both rivers are heavily polluted. The results of the clustering analysis stated that moving towards upstream-downstream the quality of water decreases along both rivers.
The spatial trend analysis of water quality parameters along the rivers plays a crucial role for identifying the spatial variation of water quality. Also, availability of clean water depends on the geographical locations and topological situation across the basin.