蒸發散是水文循環重要機制之一，對水資源經營管理、長期生態研究及水文模擬 等，蒸發散資料是不可或缺。本文旨在探討Hamon蒸發散公式於福山試驗林之應用，並以水 平衡法及宜蘭氣候站蒸發量作為比較基礎。結果顯示，從1993~1996年，Hamon公式所推估 福山試驗林年蒸發散約830~890mm，夏季時月蒸發散較高，約100~130mm，冬季時月蒸發散較 低，約30~50mm。Hamon公式推估福山一號集水區蒸發散有偏低現象，其原因可能與公式本身、 集水區地質特性及樹冠截留等有關，此外經由敏感度分析後得知，溫度比緯度對蒸發散影響 還大。Hamon公式在應用上甚為方便，對基本資料不足或研究設備尚缺集水區，利用此公式 推估蒸發散是一可行方法。本文以四年(1993~1996)資料作為福山試驗林蒸發散預估之初步探 討，當爾後資料更為齊全時，宜持續進行分析，以力求長期蒸發散研究。 Evapotranspiration (ET) is an important mechanism of the hydrological cycle, and ET data are essential for water resources management, long-term ecological research, and hydrological simulation. This study focused on application of the Hamon equation to estimate the ET of Fu-Shan Experimental Forest. The annual ET of Fu-Shan Experimental Forest predicted by the Hamon equation was 830 to 890mm from 1993 to 1996, and the ET values were higher during the summer and lower during the winter. However, when compared to the results of the water-balance method and the observed evaporation at the I-Lan weather station, it was clear that the Hamon equation underestimated ET. This may be due to the equation itself, geological characteristics of the watershed, or interception loss. In addition, a sensitivity analysis showed that temperature had more influence than latitude on ET. Because of its simplicity and few parameters, the Hamon equation has been found to be useful for estimating ET, especially for those watersheds that lack of essential hydrological data or research equipment. This study was based on the data obtained between 1993 and 1996. Further studies will be undertaken to investigate ET for long-term research when more data are available.