干旱区农田蒸散量的日间变化分析

塔里木灌区位于中国新疆的塔克拉玛干沙漠北缘 ,本区开垦前是沙漠起伏、灌木丛生的原始荒漠 ,原始胡杨林点片连绵生长于荒漠之中。 1 95 2年 3月开垦至 1 996年 ,全灌区总灌溉面积已达到 660 0 0 ha。形成了稳定的农业生态环境 ,成为塔里木盆地最大的新绿洲。绿洲内部农田蒸散的日变化规律 ,极具干旱区特点。本文通过中国科学院阿克苏水平衡试验站的观测试验和一些干旱、半干旱及湿润地区的蒸发日变化过程进行了对比分析 ,论述了干旱区蒸发日变化的某些特征。

Daytime Variation of Evapotranspiration from Farmland in Arid Region of China

Evaporation estimation is essential for water balance study, irrigation and water resources planning, etc. The variable of evapotranspiration from farmland in arid region is different from in humid region. Based on the estimation and analysis of evaporation from farmland in Aksu irrigation area, which is located at the northwestern arid region of China, direct measurement in the land or in evaporimeter, energy balance method and other methods are used to measure evapotranspiration there. Evapotranspiration from farmland in arid region mainly depends on soil moisture, water table and the growth of crops. The maximum evaporation rate in bare land without irrigation appears in the spring but in the summer. Variation of evaporation in a day is relative to wind velocity, air humidity and air temperature, and the variation of evaporation within a year is close related to air temperature. The process of evapotranspiration is different to evaporation from soil moisture or water surface. The peak of evapotranspiration curve appears earlier, evaporation increases slowly in the morning and decreases slowly in the afternoon too, which is different from the evaporation regularity in humid region. Compared with humid region, the characteristics of daily evapotranspiration from farmland in arid region are:(1)The variation of evapotranspiration rate within a day is not great as in humid region. (2)Evaporation time from farmland is 15 17 hours in a day in arid region. (3)Cresting value of evapotranspiration in a day in arid region appears earlier than that in humid region and cresting value goes on longer in arid region.