额济纳绿洲草地蒸散系数研究

联合国粮农组织推荐的蒸散计算方法中,蒸散系数是计算实际蒸散必不可少的参数。本文从蒸散系数的定义出发,在2005年额济纳绿洲生长季连续观测的基础上,运用波文比能量平衡法计算额济纳绿洲草地的实际蒸散量,利用FAO 56Penman-Monteith模型计算草地的参考蒸散,将实际蒸散与参考蒸散相除即得到额济纳绿洲草地的蒸散系数。通过研究发现:生长季草地的蒸散量(ETc)为446.96mm,从生长季初期开始,草地的蒸散量开始增加,在6月后半月达到最大值6.724mm/d,此后蒸散量开始快速下降,在生长季末期达到最低值1.215mm/d;蒸散系数(Kc)呈现出与蒸散量(ETc)相同的变化趋势,自生长季初期开始蒸散系数快速上升,在6月后半月达到生长季最大值0.623,之后随着草地生长减缓,蒸散系数快速下降,直至生长季末期草地停止生长。对额济纳绿洲草地蒸散系数的计算可以为该地区准确估算草地生态需水量提供依据。

Study on Evapotranspiration Coefficient of Grassland during the Growing Season in the Ejina Oasis

According to works of Food and Agriculture Organization of the United Nations,evapotranspiration coefficient is essential parameter to calculate actual evapotranspiration.Based on the definition of evapotranspiration coefficient and successive observation,evapotranspiration(ETc) of grassland in the Ejina oasis of northwest China was estimated by application of Bowen ration-energy balance method(BREB),and reference evapotranspiraiton was calculated by using FAO 56 Penman-Monteith model during the growing season in 2005.Then,according to the definition,the evapotranspiration coefficient of grassland was given in the Ejina oasis.During the growing season,total ETc was 446.96 mm.From the beginning of growing season,the ETc increased gradually,and reached its maximum value of 6.724 mm/d in the last fifteen days of June.Hereafter the ETc dropped rapidly,and reached its minimum value of 1.215 mm/d at the end of growing season.The variation pattern of crop coefficient(Kc) was similar to that of ETc.From the beginning of growing season,the Kc value increased rapidly,and reached its maximum value of 0.623 in the last fifteen days of June.Afterward,with slowing growth of grassland,the value dropped rapidly at the end of growing season.The evapotranspiration coefficient is helpful to estimate accurately ecological water demand of grassland in the Ejina oasis.