ABSTRACT
Climate warming is recognized as an objective reality all over the world. The typical characteristics of this warming include rise in soil and air temperature, more frequent and intensified extreme weather events (droughts, floods, storms) that especially became apparent in the recent decade, and, finally, change in precipitation patterns. In the arid areas, to which the Aral Sea basin, the research object, belongs too, more frequent dry years accompanied by decreased river water availability and precipitation and increased aridity of air are the most critical. This has a negative effect on agriculture in the basin’s countries, which is a source of livelihoods for almost half of the population. Most researchers studying the climate change effects note that the temperature rise leads to increased evaporation and, hence, to growth of water demands for irrigation of crops. The analysis made for the Fergana Valley on the basis of potential evapotranspiration proves an increase in moisture deficit during growing season through the rise in air temperature. According to REMO modeling of climatic scenarios until 2100, evapotranspiration would increase significantly by 4 - 8 mm/day in summer months. However, it is demonstrated also that the thermal potential of given area would be changing. The growth of the thermal potential causes that the sum of effective temperatures is reached in shorter period of time and the crops can be sown earlier. This, first, would reduce the crop development phases and the growing season as a whole, and, consequently, would decrease the total water use. For example, for the mid-season cotton, the growing season would become 30 days shorter and the water use would decrease by 100 mm by 2100. The thermal patterns should be considered as the basis for crop rotation and, hence, for water planning.