Reservoir Eutrophication Modeling, Sensitivity Analysis, and Assessment: Application to Karkheh Reservoir, Iran

This article presents the eutrophication modeling and management in a very long, as well as large volume, reservoir with highly fluctuating water level. The CE-QUAL-W2 model was calibrated and validated for predicting the formation of the eutrophication process in the Karkheh reservoir under different management strategies. In addition to supplying irrigation water for 180,000 hectares of irrigable area, the highly strategic multipurpose Karkheh reservoir intends to supply reliable and high-quality domestic water for a few large cities and probable transfer of drinking water to the neighboring countries. This approach identifies the most effective system parameters of eutrophication formation through the extensive sensitivity analysis. Well-tuned effective parameters resulted in satisfactory convergence to the observed field data through a 64-km long reservoir. Effects of any reduction and/or increase in total incoming nutrient loads resulting from different load management scenarios were also examined. Results of the model show that in the Karkheh reservoir under existing conditions, phosphorus is the limiting factor in eutrophication and productivity of the system.