位於大漢溪上游的石門水庫已運作超過五十年，超過55%的石門水庫配水提供桃園地區的農業及公共用水，跨流域的水資源調用特性維繫了桃園台地上的用水，而密集的灌溉埤塘在桃園台地占了不少面積，代表了此地蓬勃的灌溉需求。本研究的目的是探討氣候變遷和土地利用改變下，跨區域的水資源調用如何影響地區水文平衡，本研究使用水文、氣候觀測資料及配套經驗公式推估桃園台地的各水文分量，以兩種時期的土地利用分布探討水文分量的差異，接著根據AR5的四個氣候變遷情境，評估此區域水平衡系統如何受氣候影響。根據所蒐集並估算之資料，於1997至2013期間，台地年總入流量為19.2億噸，其中降水量為63.9%，水庫供水量為36.1%，年總出流量約為21.6億噸，蒸發散量占38.6%，入滲量占22.9%，逕流量則為38.5%。結果也顯示此段期間的氣候變異小於都市化的土地利用對水文因子造成的影響。在氣候變遷情境下，入滲量因受土壤分布及土地利用影響大，因此為較為穩定的水文因子，逕流量則是受降雨變率大而有很大的變動。本研究結果能夠做為水資源政策上的參考。;The Shihmen Reservoir has been in operation for more than 50 years and is located on the upstream Dahan River. Over fifty-five percent of the reservoir outflow is allocated from the Dahan River basin to support irrigation and industrial or domestic water usage on the Taoyuan tableland. The trans-basin water allocation and thousands of irrigation ponds on the Taoyuan tableland have created unique landscapes and hydrodynamic characteristic in northern Taiwan. Such intensively managed landscapes, regions of significant land-use change, serve as sources of economic prosperity. The objectives of the study are to assess and quantify the influence of climate change, land use and the trans-basin water allocation on the regional water budget. The assessment of the climate change was based on the AR5 scenarios released by NCDR(National Science and Technology Center of Disaster Reduction). The study uses hydrogeological observations and the associated empirical models to estimate the water budget in the Taoyuan tableland. Based on estimated results from 1997 to 2013, the total inflow volume is 1.92 billion tons per year, including precipitation(63.9%) and the allocated water from Shihmen reservoir(36.1%). The outflow volume is 2.13 billion tons per year, which can be divided into the components of evapotranspiration(38.6%), infiltration(22.9%) and streamflow(38.5%). The result also shows that the impact of Taoyuan tableland urbanization is greater than that of the climate change on those hydrofactors in this period. For the climate change scenarios, the result indicates that the infiltration component is the most stable factor. The streamflow fluctuated with the temporal trend of precipitation in the area. The research results could benefit the management of regional water resource and policy decisions.
