Managed Aquifer Recharge: The Solution for Water Shortages in the Fergana Valley

As a result of the growing demand for food and energy, the competition for water between upstream and downstream users in the Syrdarya River Basin has increased. The change in the upstream reservoir operation from a conjunctive irrigation/hydropower mode to exclusively hydropower generation resulted in reducing the river flow downstream in the summer and increasing it in the winter. This phenomenon caused a downstream water shortage of 2,000-3,000 Mm super(3)/year in the summer and an excessive, often unutilized, flow of the same magnitude in the winter. This study suggests that the current practice of sequential in-channel reservoirs is not coping well with the needs of both upstream and downstream water users. Furthermore, it examines the alternative approach of managed aquifer recharge (MAR) in the upstream of Fergana Valley with a view to adapt to new water management reality. Favorable hydrogeology conditions prevailing in the Fergana Valley are envisaged to create benefits from MAR both at local and regional levels. The study follows a stepwise procedure of implementing MAR in the Fergana Valley, starting from the regional assessment of the MAR potential to testing MAR at the pilot scale through field and modeling studies. The regional assessment shows that over 500,000 ha, or 55% of the currently irrigated land in the Fergana Valley, can be shifted from canal irrigation to conjunctive surface water-groundwater irrigation. This will reduce the return flow to the river by 30% (or by 1,000 Mm super(3)/year), and form free storages of 500 Mm super(3) in the command areas of main canals. Pilot-scale studies for Isfara and Sokh aquifers in the Fergana Valley support the results of regional assessment. Overall, groundwater development for irrigation and MAR in the Fergana Valley is expected to reduce the winter flow of the Syrdarya River at the valley outlet by 1,500 Mm super(3)/year, and consequently increase its summer flow by the same magnitude. This report proposes a major shift in the focus of development projects in the Fergana Valley, from rehabilitation of dense drainage systems to groundwater development for irrigation and MAR.