AN APPLIED METHOD FOR ESTIMATING THE AMOUNT OF WATER EXCHANGE BETWEEN THE SEASONAL RIVERS AND AQUIFER, CASE STUDY: ZAYANDEHROUD RIVER IN THE CITY OF ISFAHAN

Abstract

In most cases, the rivers that flow in the alluvial aquifers are hydraulically connected to them. So, in such areas, it is essential to determine the relationship between the river and the aquifer. In this study, hydraulic connection between alluvial aquifer of Isfahan city and Zayandehroud River are evaluated. The main recharge source of this alluvial aquifer is Zayandehroud River. In recent years from March to November, due to the shortage of water and consumption of whole of the river flow rate in the upstream of the Isfahan city, the flow to the Isfahan region is disconnected. Therefore, the November and December are those months which are respectively the end of the dry period and the start of the river flow period. Using the groundwater isopotential maps of the November and December, 2015, the hydraulic connection between the river and aquifer during the dry and wet period was compared. The obtained results show that during the period of water flow in the river, there is an effective connection between river and aquifer. In most places the river recharges the aquifer. In some parts of aquifer in the south of the river, considerable cones of depression caused by heavy pumping have been created which changed the normal pattern of groundwater flow to a forced recharge from the river. Most recharge to the Isfahan aquifer by the river occurs in the western part of the city till the region of Khajo Bridge. The amount of this recharge is about 55028 m3/day.