Lowland transboundary river in a cold, semi-arid steppe: review of the Yesil River basin

Yesil River is one of the longest transboundary rivers in Kazakhstan and is representative of northern Kazakh hydrology. Shared between Kazakhstan and Russia, it is the main water source in the region with high strategic importance. Regions with characteristics like Yesil River basin are underrepresented in the scientific literature. Review of climatic, hydrological and other basin characteristics is provided using global remote sensing and reanalysis datasets, historical recorded data and review of international and local research papers. Overall, the basin is characterised by very low runoff ratio (0.04–0.07) and moderate aridity index. Evapotranspiration dominates the water balance and warm season precipitation is fully consumed by this flux. Spring snowmelt generates most of the streamflow during a short period, storage of which controls water availability until the next spring. In addition, snowmelt causes devastating floods and controls groundwater recharge. Currently, water use in the basin accounts for 18% of annual runoff, although it is increasing. Future projections indicate significant warming and uncertain precipitation patterns, which might significantly increase runoff in spring and increase region’s aridity due to increased atmospheric water demand. Future transition to more arid climate zone poses a risk to local rain-dependent agriculture (covering half of the basin). As a result, irrigated agriculture in addition to continuing industrial and urban development might substantially increase future water use. Considering the current state and providing hydrological insights for the region, the key knowledge gaps for this basin and region are presented.