The Hydrological Cycle of Central Asia under Climate and Land Use Changes assessed by a re-gional climate model with novel schemes for irrigation and inland lakes

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Central Asia represents a paradigm of large-scale irrigation in arid and subtropical climate zones, respectively. For example, the associated shrinking of the Aral Sea is well known. In contrast, our knowledge of the effect of irrigated agriculture on the regional water cycle in Asia is fairly limited. It can be assumed that evapo-transpiration from open water tables and partly dense vegetation cover in the lowlands along the Syrarya and Amudarya rivers is substantial given partially low cloudiness and high global radiation during summer. It is ignored whether the resulting water vapor is con-densed within the catchments of these rivers, hence intensifying the hydrological cycle and enhanc-ing water supply in the region, or is rather subject of advection over the Central Asian mountain ranges towards other river catchments. As such, irrigation could also play a positive role for water availability. The planned project HYDRASIA is dedicated to this issue by developing a sophisticated climate model approach, which accounts for those components of the water cycle that are relevant to irrigation and inland lakes in Central Asia. This mainly includes a novel representation of irrigated agriculture and inland lakes in the climate model. The research project is mainly focused on model development with respect to the land surface scheme in the regional climate model REMO, driven at a horizontal resolution of 50 km and 10 km. According to availability, it is also planned to use the new non-hydrostatic version of REMO at an even higher resolution. The extended and calibrated REMO version will then be employed for long-term simulations with greenhouse gas and land use scenarios until 2100. On the one hand, the goal is to assess the impact of global climate change on future wa-ter availability and general boundary conditions for irrigation in Central Asia. On the other hand, the feedbacks of irrigation, i.e. its regulative effect, on the future regional climate will be quantified.