Groundwater resources management for public water supply in Changhua County, Taiwan - 2. The influence of climate change

This is the second paper for a sequence of studies. Niaozueitan Artificial Lake supplies surface water for Changhua County to reduce the use of groundwater and mitigate the subsidence problem. The study develops a groundwater model to simulate the groundwater level variation, estimate the uplift of groundwater level, and evaluate the groundwater position factor (P) and groundwater management index (GMI) under different scenarios. From the generated river flow under plausible climate change scenarios, the intake and supply of Niaozueitan Artificial Lake are evaluated and then the lack of water resources in Changhua County is estimated. The results show that the circumstance of A2 miroc3_2_medres induces the largest lack of water resources (101,800 tons/day), and thus it is defined as the worst GCM. Under the worst GCM situation for the scenarios of water supply of 300,000 and 250,000 tons/day by Niaozueitan Artificial Lake, the cumulative uplift of the four aquifers for these two scenarios are 10.40 and 7.25 meters, respectively, in 2061 and the mean uplift for each aquifer is similar. The large uplift areas present around the foothills of Pagua mountain and declines to the fantail. Considering the worst GCM situation, the groundwater resources in Changhua County will reach a water scarcity after 2041 under the maintained pumping situation. In the scenario of supplying 300,000 tons/day by Niaozueitan Artificial Lake, the GMI value locates in the warming condition until 2061 and shows a decreasing trend. In the scenario of supplying 250,000 tons/day by Niaozueitan Artificial Lake, the GMI value reaches the constraint condition after 2058. The results show that Changhua County will face a water scarcity in the future under the climate change effect even if Niaozueitan Artificial Lake is developed. New water resources and strategies should be considered to reduce further groundwater use. The study results provide the references for the water resources plan and management in Changhua County under the climate change effect in the future.