The Impact Assessment of Water Transfer from East to West of Tehran on Groundwater Quallity

Tehran is a rare example of a major city in the world, which lacks a centralized storm water and sewer collection network. Runoffs origination from the southern slopes of Alborz Mountain are collected by means of a series of traditional, above ground small canals leading to three main collectors. These channels are passing through densely populated areas and industrial zones where industrial as well as domestic wastewater are directly discharged them.The most part of these polluted waters along with the underground water from the southern part of these polluted waters along with the underground water from the southern part of Tehran aquifer are used for irrigation purpose in over 13000 hectares of agricultural lands located in the southern part of Tehran within the boundary of the study area.In this paper, four alternatives have been considered as follows:- Existing situation without any water transfer,- Transfer of 5 m3/s of surface water,- Transfer of 10 m3/s of surface water,- Transfer of 15 m3/s of surface water,In each alternative the variation of concentration of heavy metals, Chromium, Cobalt, Cadmium, Nickel, Lead, Zinc, Iron, manganese and Copper in Tehran aquifer was computed by a computer program for a period of twenty years.The results show that in the case of not transferring any water, the concentration of heavy metals will generally increase. The groundwater level will also increase considerably. But if the wastewater is transferred, the contaminat's concentration will considerably be decreased as follows:In second and third alternatives, the rate of increase of heavy metals concentration will decrease substantially and the water level will be decreased in an acceptable manner.In the fourth alternative all of the surface water will be transferred and the only major source for irrigation purpose will be the groundwater.