Water quality, potential conflicts and solutions—an upstream–downstream analysis of the transnational Zarafshan River (Tajikistan, Uzbekistan)

The Central Asian countries are particularly affected by the global climate change. The cultural and economic centers in this mostly arid region have to rely solely on the water resources provided by the rapidly melting glaciers in the Pamir, Tien-Shan and Alay mountains. By 2030, the available water resources will be 30 % lower than today while the water demand will increase by 30 %. The unsustainable land and water use leads to a water deficit and a deterioration of the water quality. Documenting the status quo of the water resources needs to be the first steps towards an integrated water resource management. The research presented here provides a detailed overview of the transboundary Zarafshan River, the lifeline for more than six million people. The findings are based on field measurements, existing data from the national hydrometeorological services and an extensive literature analysis and cover the status quo of the meteorological and hydrological characteristics of the Zarafshan as well as the most important water quality parameters (pH, conductivity, nitrate, phosphate, arsenic, chromate, copper, zinc, fluoride, petroleum products, phenols and the aquatic invertebrate fauna). The discharge of the Zarafshan is characterized by a high natural discharge dynamic in the mountainous upper parts of the catchment and by sizeable anthropogenic water extractions in the lower parts of the catchment, where on average 60.6 % of the available water is diverted for irrigation purposes in the Samarkand and Navoi provinces. The water quality is heavily affected by the unsustainable land use and inadequate/missing water purification techniques. The reduced discharge and the return flow of untreated agricultural drainage water lead to a critical pollution of the river in the lower parts of the catchment. Additional sources of pollutants were identified in the Navoi special economic area and the mining industry in the Tajik part of the catchment. The impact of the global climate change and the socio-economic growth on the water availability and the water demand will aggravate the detected problems and might lead to severe local and transboundary upstream–downstream water conflicts within the next decades.