Evaluation of Sustainability of Groundwater development in a Multilayer Aquifer (case study: Aquifer of Golestan province)

Evaluation of a system needs a combination of indicators that can show their current situation and future. Multilayer aquifers are more complicated due to different recharge and discharge processes of each layer. This paper aims to evaluate sustainability of phreatic and confined layers of an alluvial aquifer in Golestan province. The relevant data includes monthly precipitation of 19 rain gauges, groundwater level of the phreatic layer in 19 observational wells and piezometric level of 19 wells in the confined layer. In this paper combination of eleven indices that selected according to available data in the region, is used to assess sustainability. Results show in spite of detecting no significant trend in the precipitation data, there is descending trend in the water table of phreatic layer and piezometric level of confined one. Aquifer sustainability index of phreatic and confined layers are 0.89 and 1.01, respectively, that means unsustainability of both layers and worse condition of confined layer. Of course unsustainability of the confined layer has been covered by existed non-renewable groundwater resources. According to groundwater abstraction development index equal to 0.26, implementation of water resources development plans is allowed with considering limitations in terms of water quantity and quality. Also 2.82 as the aquifer recovery potential index revealed if driver factors change toward providing sustainable conditions, both layers can be recovered soon. It can be concluded that the region is facing water scarcity that is a limitation to economic development and human health and well-being.