Modeling the managed aquifer recharge for groundwater salinity management in Sokh River basin

                                   A.Karimov, I.Gracheva, F.Miryusupov, M. Yakubov
                       

Abstract

Vulnerability of surface water sources in the Syrdarya River basin, due to their transboundary nature and climate change, raises importance of the shift from canal irrigation to conjunctive use of surface and groundwater resources. However, groundwater development for irrigation may increase salinity of water in the shallow aquifers due to leaching of dissolved solids from salt-affected vadoze zone. This may also gradually effect to quality of the fresh groundwater in the deeper aquifers which are the source of drinking water supply in the region. In this paper managed aquifer recharge and discharge is analyzed as a strategy to maintaining the groundwater quality of Sokh aquifer, one of the aquifers of Fergana Valley located in the upstream of Syrdarya River basin. The modeling study examines groundwater salinity change over a five-year period with four scenarios: (1) the current situation with under developed groundwater use (Base Scenario); (2)  increased groundwater extraction in groundwater natural recharge zone (High Scenario); (3) managed aquifer recharge in winter and increased groundwater extraction in summer in groundwater natural zone (Scenario MAR); (4)  MAR in winter in the natural recharge zone and increased groundwater summer extraction using shallow wells in the discharge zone (Scenario MARD). The modeling results showed: salinity treat in the topsoil under Base Scenario due to shallow water table, and; no groundwater salinity change in the deep aquifer. The studies found the salinity increase in the High scenario in the shallow and deep aquifers due to downward saline water flows. The results indicate that MAR in the natural recharge zone maintains good quality of water in the deep aquifers of Sokh River basin, while shift from deep wells of 60-100 m deep to shallow wells 25-30 m contributes to maintaining suitable for irrigation water quality in the shallow aquifers.

Keywords Managed aquifer recharge, groundwater use for irrigation, numerical modeling and scenario analysis, Central Asia, Fergana Valley