石門水庫是北台灣的重要水庫，具有給水、灌溉、防洪、發電等多元功能，近10年的平均年供水量約8億立方公尺，相當於超越機率56%入流量，但枯水期平均入流量僅佔全年21.3%，且與枯水期計畫用水量間尚有5,451萬立方公尺的缺額，需仰賴水庫蓄存水量來補足，若水庫蓄水量在豐水期結束前仍不理想，則可能面臨缺水風險。本研究由農業用水觀點，分別利用農田水利會灌溉計畫書及CROPWAT model探討調整耕期、灌溉期距、錯開日數等不同灌溉管理模式對枯水期農業用水的影響，其中耕期延後10~20日時，因稻作生育期往高溫的夏季遞延，期作總用水量略增1.8%~4.5%，枯水期用水量則可減少9.5%~23.2%，對石門水庫的枯水期用水調度有很大助益，在某些情境下，提前打折加上延後供灌，尚可取代停灌措施或減少停灌面積。此外，利用TCCIP所推估近未來(2020-2039年)大漢溪流域水文與氣象參數改變量，模擬近未來氣候變遷對農業用水量及石門水庫用水管理的影響，溫度增加及枯水期雨量減少使農業用水量較現在增加2.2%~3.1%。而未來枯水期水庫入流量僅為現在的88.4%，水庫的用水管制強度需較現在更高，當入流量為超越機率80%時即需提前打折並延後供灌、當入流量為超越機率90%或95%時，均需停灌桃園水利會灌區才能確保水庫蓄水量在安全範圍以上。;The Shimen Reservoir is the major reservoir in northern Taiwan to serves a number of purposes, including irrigation, hydroelectric power, domestic and industrial water supply, fold prevention and sighteeing. The average year-supply of the last decade was about 8x108 m3. The amount of inflow in dry season or wet season was evidently different. The inflow in dry season account for 21.3% of the average year-inflow and with the shortage of 54.51 million m3 by the water resource plan in the last decade. If the storage was insufficient by the end of wet season, the potential risks of water shortage would be increasing. This study used the CROPWAT model and Irrigation Plan to analysis the effect of adjusting the farming schedule, irrigation interval, and rotation interral on irrigation management in dry season. And use the variation data of hydrological and meteorological parameters estimated by TCCIP to simulated the scenarios of water management of the Shimen Reservoir, to explore the impects of climate change on agricultural water management.
