The influences on groundwater and subsidence under the water supply of Niaozueitan Artificial Lake in Changhua

It is important to find new water resources and replace the use of groundwater to mitigate the problem of subsidence in Changhua. The project of Niaozueitan Artificial Lake is proposed to alleviate the problem. Niaozueitan Artificial Lake is designed for supplying water for Caotun and Changhua in 2031. A combination of additional surface water supply from Wu River and original groundwater use in Changhua can reduce the quantity of groundwater pumping. Therefore, the groundwater resources can be rehabilitated and the subsidence can be reduced. This study used a numerical model to evaluate the influences on groundwater resources and land subsidence under the supply of water resources from Niaozueitan Artificial Lake. The results showed that groundwater levels in the four aquifers in Changhua in 2031 will increase 4.17 m and 5.18 m, respectively, in the cases of water resources move and do not move back to Taichung. The increasing quantity of groundwater level is relatively large in the third and fourth aquifers due to the cease of pumping wells that are mostly located in the those aquifers. The reduced maximum subsidence rates are 0.25 cm/year and 0.38 cm/year, respectively, in the cases of water resources move and do not move back to Taichung. The reduced areas with a subsidence rate larger than 2 cm/year are 32.75 km² and 42.39 km², respectively, under the same scenarios. The investigations showed that the development of Niaozueitan Artificial Lake leads to a positive effect in the Changhua area for both groundwater resources and land subsidence. In addition, the study results can be applied to future development of Niaozueitan Artificial Lake.