Application of IRWQISC Index in the Water Quality Evaluation of Dam Reservoirs (Case Study: Golabar Dam Reservoir, Zanjan)

The Evaluation of the quality of water resources using numerical models and qualitative indices has recently been considered by many researchers. In the present study, the thermal and qualitative stratification of the Golabar Dam reservoir, located in Zanjan, Iran, was investigated. In addition, the water quality was evaluated at different points of the reservoir at different times using the IRWQISC (Iran Water Quality Index) index. For this purpose, the 2-D CE-QUAL-W2 numerical model was used for the hydrodynamic as well as the dissolved oxygen and total dissolved solid simulation for the 1-year period of 2014 to 2015. The simulation results indicated a summer thermal stratification period from mid-March to mid-September. The water quality evaluation indicated a good water quality of the top layer of the reservoir during the six warm months of the year with an index of 75. On the other hand, the water quality of the sub-layer dropped from the good with an index of 75 to a rather bad class with an index of about 40/5. In addition, in the six cold months of the year, the water quality improved from the middle class with an index of 46 to the good class with an index of about 77. In general, the spatial and temporal study of the water quality of the dam reservoirs using different water quality indices such as IRWQISC can significantly help in determination of the water quality and providing management strategies for the verification of the water draw-off elevation, optimal water usage as well as providing solutions for improving the water quality in the reservoirs.