Water is central to the productivity of the Great Plains. Projected increases in winter and spring precipitation in the Northern Plains may benefit productivity by increasing water availability through soil moisture reserves during the early growing season. The Northern Plains will remain vulnerable to periodic drought because much of the projected increase in precipitation is expected to occur in the cooler months while increasing temperatures will result in additional evapotranspiration. In the Central and Southern Plains, projected declines in precipitation in the south and greater evaporation everywhere due to higher temperatures will increase irrigation demand and exacerbate current stresses on natural ecosystems. Adding to climate change related stresses, growing water demands from large urban areas are also placing stresses on limited water supplies.