Hydrological responses to climate change and irrigation in the Aral Sea drainage basin

Hydrological model interpretation of the water flow development in the Aral Sea Drainage Basin (ASDB) indicates that the water diversion and irrigation schemes in this region have considerably increased evapotranspiration and thereby decreased net water flux (precipitation minus evapotranspiration) from the atmosphere to the surface of the ASDB. Increased evapotranspiration cools the irrigated areas, and the decrease of net atmospheric water influx to the ASDB may also have non-local effects outside the basin. Such effects have previously been estimated by atmospheric modeling, assuming a global average evapotranspiration return flow to the atmosphere of about 40% of irrigation. Our results indicate larger return flows, of nearly 100% of the applied irrigation water in the ASDB, which may also imply considerably larger than previously estimated non-local water and climate effects of the world's irrigated areas.