The objective of this study is to evaluate the impact of climate change on water resources. An integrated procedure is proposed for assessing the response of a water resources system to climate change on the scale of a basin. The Zhoshui River basin in central Taiwan was selected for the impact assessment. Five downscaled general circulation models based on the A1B scenario for 2046–2065 were adopted to assess the impact of climate change, including (1) the irrigation water requirement downstream of the basin, (2) the river flow upstream of the basin, and (3) the water resources utilization related to supply and demand in the basin.
Rising temperatures will cause irrigation water requirement to increase by 10%. Additionally, precipitation in the basin will substantially decrease and will likely cause a 20% decrease in river flow. Thus, irrigation water shortages may become more severe in the future. As an adaptation, Hushan Reservoir, which will begin operation in mid-2016, can assist in offsetting domestic and industrial demand. In addition, to maintain the irrigationdeficit at the present level (2001–2010) in the future, conveyance losses should reduce to 30% and the farming area used in the second paddy growth season should decrease by 10%.