Effect of reservoir size on water quality in coastal reservoirs during desalinization period using numerical model

Coastal reservoirs are water storage structures constructed near the river estuary to supply water to coastal areas. One of the most important aspects related to performance of these structures is the effect of reservoir size on the flow and water quality. For this purpose, MIKE3, a 3D numerical software was used in the present work. The case study included proposed coastal reservoir located on the coastlines of the Caspian Sea in the vicinity of Tajan River estuary. To conduct this research, 4 types of reservoirs with different sizes were considered. Input parameters to the model included 5-year flood of Tajan River, initial reservoir salinity and ambient temperature data. The results showed that construction of shallower reservoir due to better surface and depth mixing could achieve higher water salinity during desalinization period. Furthermore, the most water temperature change value was determined after passing hydrograph peak discharge, which shows the effect of inflow on reservoir water quality. Finally, the results of water density revealed that the decreasing trend of water density occurred mostly due to decreasing of water salinity in the reservoir.