The effects of water stress on croplands in the Aral Sea basin

Water scarcity constitutes an important challenge faced by croplands in the Aral Sea basin (ASB). The croplands in the ASB are highly vulnerable to water stress and land degradation and experience high anthropogenic disturbances. This study investigated the spatiotemporal patterns of water stress and land degradation and detected the years with abrupt changes in the water stress index (WSI) by applying linear regression analysis and the breaks for additive seasonal and trend (BFAST) method. Furthermore, these analyses were combined with statistical data on water intake to explore the relationship between water stress and land degradation in the sub-basins. The results revealed that water stress was more serious in the downstream areas than in the upstream area. The downstream regions experienced increasing water stress, resulting in severe land degradation and cropland abandonment. The BFAST results indicated that abrupt changes in the WSI mainly occurred in 2005, 2008 and 2010. The correlations between water intake, water stress and land degradation in the lower reach were stronger than those in the upper reach. Subsequently, the water intake had a great influence on the cropping intensity and cotton yield in the downstream regions. Water stress in different regions was caused by different drivers. In the upstream areas, precipitation was the major driver of water stress in crops. In contrast, the water allocation in the middle and lower reaches was affected by anthropogenic disturbances and resulted in serious water deficits in the Amudarya River delta in 2000 and 2008. Because each country had a unique irrigation scheme and cropping pattern, obvious spatial differences in water stress and land degradation changes were detected between Tashauz and Karakalpakstan. This study can provide a decision-making reference for the implementation of sustainable development goals in the ASB. (C) 2020 Elsevier Ltd. All rights reserved.