| dc.description.abstract | Water resources are not easy preserved in Taiwan due to our uneven spatial and temporal distribution of precipitation. In recent decades, some forests and agricultures have become impermeable lands due to our rapid development of urbanization. It may affect surface runoffs and groundwater recharges in a watershed. In addition, the climate change has confirmed to influence local precipitation pattern, and further to affect water resources. In order to improve our understanding the effects of land cover changes and climate changes in a watershed, this study selected Hsinchu Fengshan River basin as study site and applied WASH123D numerical model to simulate watershed flow variabilities. We used two periods of hydrological records (June of 2011 and May of 2012) to calibrate model parameters and validate its performance. Calibrations indicated that the value of R-Square (R^2) is above 0.8 and the Root-Mean-Square Error (RMSE) is less than 0.2 m. It means a good performance on model calibration is conducted. And then we implemented these setups for further simulations of designed scenarios. Three scenarios of land cover changes with future scenarios (2020-2040 years) have designed. Results of groundwater levels are all slightly increase as land cover has changed. Scenario 1, which is unrestricted developing in a watershed, shows river stages increase 0.32 cm in wet season, and rise 0.26 cm in dry season. Scenario 2, which forests are preserved, shows that river stage increases 1.34 cm in wet season, and increase 1.21 cm in dry season. Scenario 3, which hillside is restricted to develop, groundwater level increases 1.55 cm in wet season, and increase 1.36 cm on dry season. However, the trend of groundwater level reveals some variations under climate changes. Groundwater level decrease 0.7 cm on RCP2.6 scenario, and decline 0.15 cm in dry season of RCP8.5. For the plum rain season, it has 3.38 cm decreasing as using RCP2.6, and decrease 2.56 cm of RCP6.0 scenario. For typhoon season, groundwater levels increase 1.26 cm on RCP2.6, and decrease 0.15 cm on the RCP6.0 scenario. In general, this study concluded that the effects of groundwater levels in Fengshan River basin caused by climate changes have more obviously vibrations than land cover changes. | en_US |