Future water demand for agriculture in the arid regions as inferred from an ensemble of RCM projections

Abstract:

The economy of arid regions is largely based on irrigated agriculture, which critically depends on water availability. The latter requires an accurate estimation of water balance components to develop an optimum strategy of water consumption across arid regions (a good example of this is Central Asia). Typical spatial scales of irrigated lands (about 10 km) not captured by the majority of up-to-date RCMs and can be explicitly described using a hires mathematical atmospheric boundary layer model (ABLM) embedded into an RCM system. Here a 30-member ensemble of regional climate projections at 25 km resolution and a sophisticated 150-level ABLM has been used aimed to downscale the changes in temperature and water balance components over the irrigated lands in the Central Asia under RCP8.5 IPCC scenario by 2050-2059 relative to 1990-1999. The analysis shows that the deficit of moisture over the irrigated areas is projected to increase by the mid-21st century during the growing season. This implies that the conditions for cultivating traditional agricultural crops (primarily wheat and cotton) in the region will deteriorate if the irrigation water supply remains unchanged in the future. Changes in future water deficit over irrigated lands are estimated in terms of water volume and compared against water duties currently in effect. Projection uncertainties with respect to interannual and multiyear climate variability associated with the global atmospheric and oceanic forcings are evaluated. The study is supported by the Russian Science Foundation (grant №16-17-00063).