عنوان مقاله [English]
The study of the flow mechanism in multi-layered aquifers is important in managing their operation. So, the aim of this research is to investigate mechanism of groundwater flow in Marand double-layered aquifer in East-Azerbaijan province. The aquifer is unconfined at the east of the plain, however extending a clay layer form central parts to the west causes formation of a confined aquifer beneath the unconfined layer. The method of study consists of using groundwater levels in Oct. 2012 in the wells drilled in each layer, geophysical data, drilling logs and groundwater quality data. Combining these data, the areal extents of the aquifer layers were firstly verified and then their hydraulic connections were investigated. The results show water-table location above the piezometric level, but vertical flow is not probable due to the high thickness and low permeability of the clay confining layer. Groundwater is not exchanged through pumping wells when they are in operation, too. The results show that the confined layer is a part of the main unconfined aquifer, behaving as confined due to extension of the clay layer at the top. The low storage coefficient causes more declines in piezometric level that must be considered in management of aquifer withdrawal. Hydrochemical investigations confirm flow mechanism, showing recharge of the confined layer from south-eastern parts of the unconfined layer.