Solutions for Improving Water Quality in Dams' Reservoirs (Case Study: Ilam Reservoir)

This study aimes to investigate the thermal regime and eutrification of Ilam reservoir using CE-QUAL-W2 model and presents options for improving the water quality of Ilam reservoir in future.One of the main advantages of modeling in water quality management is using the model as a useful tool in the management of water resource quality and to evaluate the results of different management scenarios. In this regard, the CE-QUAL-W2 model simulation was performed at various input nutrient load and output flow scenarios of reservoir and the results were analyzed. The results of the model indicate the existence of thermal summer stratification and consequently quality stratification in Ilam reservoir .Based on existing indexes, cassification of eutrification for Ilam reservoir is between mesotrophic and eutrophic.Nutrient load scenarios analysis results indicate that the reduction of nitrogen and phosphorus by 50%, improved eutrification condition from eutrophic to mesotrophic. Also different scenarios analysis of water withdrawal levels of the reservoir, resulting in withdraw of reservoir in the months of September to October in terms of dissolved oxygen and total phosphorus parameters, the output level of 940 masl improved water quality.Water discharge scenario resulted from the hypolimnion to 7 million cubic meters per year (at the time of minimum concentration of dissolved oxygen) represents an increase of 1.61 milligrams per liter of dissolved oxygen in the next year at the same time.This is indicating the effectiveness of this method in increasing the dissolved oxygen in hypolimnion and consequently increase of the output water quality of the reservoir.