基于能量平衡法的黑河中游灌溉渠道蒸发量估算

The evaporation from irrigation channels estimated by energy balance method in the middle reaches of the Heihe River

干旱区绿洲农田需要通过渠道引水进行灌溉,在此过程中蒸发损失不可避免,尤其是在渠系广泛分布的情况下,蒸发损失量大,如何估算这部分量对于干旱区水资源管理至关重要.以甘肃张掖绿洲灌溉渠道为研究对象,采用Mihara所提供的基于能量平衡理论的经验方程,对渠道蒸发量进行了估算.结果表明:蒸发率在晴天时白天大于夜间,阴天时白天和夜间相差不大,气温和相对湿度是影响蒸发率的主要因子.累计蒸发量在晴天时白天是夜间的2倍左右,阴天时白天和夜间相差不大,蒸发率是直接原因.

Oasis farmland in arid regions mainly depend on water diversion for irrigation by canals, where a large deal of water is evaporated from the canal surface, especially under the condition that the channel distributes widely in the oasis, so estimating the evaporation from canal surface is very significant for water resources man- agement. In this paper, canals in Zhangye Oasis are taken as the main research object, and the evaporation from canal surface is estimated using an empirical equation, which was based on energy balance and proposed by Mi- hara. It is found that （ 1 ） when it is sunny, evaporation rate in the daytime is significantly larger than that in the nighttime, but it does not different a lot between daytime and nighttime when it is cloudy. Air temperature and relative humidity are the key factors to evaporation rate; （2） when it is sunny, cumulative evaporation in the daytime is about twice as much as that in the nighttime, but almost the same in daylight and at night when it is cloudy. Evaporation rate is the dominant factor.