利用FAO Penman-Monteith公式计算了黑河流域中游地区农田、草地和荒漠3种不同下垫面条件下的实际蒸散量, 分析了1967-2000年近35 a蒸散量的变化规律及季节变化特性, 并结合黑河中游甘州(张掖)、临泽、高台和民乐这4个地区的3期遥感影像资料分析了1967、 1986、 2000年的土地利用变化, 最后根据计算的实际蒸散量计算这3种不同下垫面条件下的总蒸散量. 结果表明: 黑河流域中游平原区陆面蒸散量总体呈现减小的趋势, 农田、草地和荒漠3种下垫面条件下的多年平均蒸散量分别为762 mm、 285 mm和229 mm; 蒸散量的季节变化差异较大, 其季节变化在这3种下垫面条件下都表现为夏季实际蒸散量＞春季＞秋季＞冬季, 实际蒸散量受季节变化的影响较为明显; 同时这4个地区的土地退化较为严重, 其中, 草地退化较为明显, 荒漠面积明显增加, 农田面积也有所增加; 在1967年4个地区的3种下垫面条件下的总蒸散量为37*10~8 m~3, 而1986年的总蒸散量为38*10~8 m~3, 2000年的总蒸散量为39*10~8 m~3.

In this article, the FAO Penman-Monteith formula is used to calculate the real evapotranspiration for different underlying surfaces in the middle reaches of Heihe River, and the evapotranspiration change and its seasonal variation are analyzed for the recently 35 a (1967-2000 year). The remote sensing images (TM) of 1967, 1986 and 2000 in Ganzhou, Linze, Gaotai and Minle Counties are used to analyze the land use change. Finally, the total evapotranspiration of the three underlying surfaces was calculated through real evapotranspiration and different areas of land. The result indicated that land surface evapotranspiration overall presents a decreasing tendency. The annual mean evapotranspirations of the farmland,grassland and desert are 762 mm, 340 mm and 229 mm, respectively, in the recent 35 a. The evapotranspiration varies seasonally. The seasonal variations of real evapotranspiration for the three underlying surfaces follow that in the summer > in spring>in autumn>in winter. Real evapotranspiration is influenced by the seasonal variation. Simultaneously, in the four counties land is degenerating seriously. As a whole, the grassland degeneration is more obvious, the desert area increases in evidence, and the farmland area increases a little; For the four counties and for the three underlying surfaces, the total evapotranspiration was 37*10~8 m~3 in 1967, 38*10~8 m~3 in 1986 and 39*10~8 m~3 in 2000.