在黑河流域中游的张掖绿洲区建立了大田环境下的春小麦和夏玉米间作农田能水平衡研究观测点,以气象观测资料为基础,采用波文比能量平衡法(BREB)和参考作物蒸散量-作物系数法(ETo-Kc)对作物的蒸散进行了计算.结果表明:在一个完整的生长期内,利用波文比能量平衡法得到的间作作物蒸散量为688 mm,日均3.4 mm/d,用参考作物蒸散量-作物系数法得到的作物蒸散量为666 mm,日均3.3 mm/d,两种计算方法得到的蒸散量总值差别小.同期,水文平衡法计算结果为733 mm.利用波文比能量平衡法所得结果的分析表明,试验地在不同生长阶段,ET变化剧烈,生长初期、中期、末期分别为1.19、4.41和2.58 mm/d,其蒸散量分别占全年蒸散总量的7.79%、78.73%和13.48%.ET月变化显示,3月维持在一个较低水平;4月和5月剧烈增加;6月达到最大;此后的7月和8月降低,但仍维持在一个高水平;9月,随着作物进入生长末期,蒸散急剧减小.对ET日内变化分析可知,作物蒸散开始于早晨7:00～8:00,在14:00左右达到最大,19:00～20:00趋于0 mm/d.不同生长阶段蒸散强度差异明显.

Data of a field experiment carried out at Zhangye Oasis, an arid region of northwest China, were used to evaluate the evapotranspiration during the 2004 growing seasons of an intercropping field of spring wheat and summer maize. The evapotranspiration was obtained mainly by two methods; Bowen ratio-energy balance (BREB) and reference crop evapotranspiration-crop coefficient (?T0 - Kc) method. The analysis results show-that in a whole growing period, the total ?Tis 688 mm and a daily mean 3. 4 mm/d by BREB, while a total of 6 66 mm and a daily mean 3. 3 mm/d by ET0 - Kc, A close result (733 mm) is also obtained by Soil Water Balance (SWB) method. Using the results of BREB, some conclusions are drawn as follows. The -ET varies with growing stages. At initial growing stage, middle growing stage and the end growing stage, the ET values are 1.19 mm/d, 4. .41 mm/d and 2. 58 mm/d, and with the percentages of total ET of 7. 79% , 78. 73% and 13. 48% , respectively. In March, ET maintains in a lower level. In April and May, the ET increases sharply. It reaches the maximal value in June. After that, it decreases lightly and gradually in July and August. With the ending of growing, the ET decreases rapidly in September. Hourly ET analysis shows that at 7 '- 00^8 ! 00 a. m. , the evapotranspiration begins, at 14 : 00 it reaches maximal value and at 19 : 00~20 ' 00 p. m. , the evapotranspiration stops. The hourly intensity of ET at different stages varies greatly.