An assessment of water withdrawal effect on water quality of the downstream river at the Mamloo Dam site using the QUAL2E model

Mamloo Dam is under construction downstream of the Jajrood River to supply Varamin plains irrigation water, flood control and produce energy. The river water quality as DO, BOD and temperature and its self-purification capacity was studied to define the minimum safe water flow downstream of the dam. The results show that the water quality will not change considerable upstream of the Parchin complex. However, after the complex outfall, the river water quality changes severely; even the effluent is treated up to National standard levels. The main reasons for the changes in river water quality are Parchin high water withdrawal as well as the high ratio of its effluent to the river flow. The dam construction will raise this effect significantly. The results show that national effluent standards, which are based on pollution concentration without considering waste loads and receiving environmental conditions in some cases cannot be satisfied and promulgation and enforcement of effluent standards are necessary.