氣候變化加劇使得降雨量、蒸發散、溫度、含碳量等等現象產生與以往不同的變化，本研究探討桃園灌溉區中從1971至2005年間的年最大降雨量，並利用克利金法(Kriging method)、面積遞減因子(Areal reduction factors，ARF)來分析降雨量在空間上隨時間的變化情況。 最後將推測出之可能降雨趨勢來與灌溉區域中因作物生長期不同而變化之作物需水量作探討。 結果顯示降雨量在濕季中近十年5、6月平均分別較過去下降26.2公厘及67.3公厘， 9月則增加94.8公厘，乾季而有越來越乾燥的情況，因此於桃園灌區中乾季時間可能有拉長之趨勢，而面積遞減曲線則分析出乾季及濕季降雨於累積面積20%處會產生較大的變化量。 作物蒸發散量計算出的田間需水量，其中有效降雨量之增減對於供水量亦需有相對的調整，但一期作草漯、大園等灌區卻未滿足田間需水量，二期作八月近年降雨量增加，而以二十年第四枯水月法計算的值可能有太過低估知情況，因此桃園灌區之供水量可能需因近年降雨分布及量的改變而作調整。 This research analyzes the annual maximum rainfall intensity of Tao-yuan irrigation region during 1971 to 2005. The Kriging method and Areal Reduction factors (ARF) are used to analysis the time and spatial variation of rainfall. The estimation of possibility rainfall pattern was discussed with the water requirement in fields during each corps growth period. In one hand, the result shows the average precipitation of wet season, May and June, in recently decade decrease by 26.2mm and 67.3mm, respectively. On the other hand, a 94.8mm increase is shown in September. Therefore, the trend of wet season period was expected to extend. The analysis of areal reduction curves also showed larger difference for the region of 20% accumulation area. Due to that the corps evaporation was related to the water requirement in fields, the irrigation water supply must also be adjusted to account for the variation of effective rainfall. The Cao-Ta and Da-Yuan irrigation areas suffered insufficient water requirement in first paddy season, while the rainfall increased in recent August during second paddy season. The calculation of the forth dry month of twenty years method might underestimate the amount of effective rainfall. Therefore, the water supply requirement in Taoyuan irrigation areas should be adjusted to take into account the variation of rainfall distribution in recent year.
