西北干旱内陆盆地区裸土蒸发强度

摘要

Owing to the vadose zone evaporation water from the ground surface,finding out the bare soil evaporation rule has important meaning to study some vadose zone water and underwater evaporation problems.To find out the rule of bare soil evaporation intensity in northwest arid inland basin,we analyze the vadose zone cross section water flow features with weather data and calculate the bare soil evaporation intensity adopting the finite-difference method through developing some bare soil water content and vadose zone pressure monitoring site experiments.Express as a result:According to vertical transportation different status of some vadose zone water,the cross section in the bare soil area vadose zone is divided into the vadose zone water upward to transfer zone and the vadose zone water downward to move zone.The extreme limit evaporation depth is 1.2 m in the bare soil zone of Northwest arid inland basin.Subjecting to the external space weather evaporation ability and the vadose zone water upward to transfer ability,the bare soil evaporation inside the basin appears in the second half month of April to the second half month of September,among which the bare soil evaporation quantity in the second half month of April to May is the biggest,and the evaporation intensity reaches to 0.56 mm/d on the average.The percentage of the bare soil evaporation intensity only equivalent to surface evaporation intensity on the average of 3.5%,as biggest as 6.7%.%鉴于包气带蒸发的水分是从地表散失，故查明裸土蒸发规律对研究包气带水分蒸发、潜水蒸发问题具有重要意义。为了查明西北干旱内陆盆地区裸土蒸发强度规律，通过开展裸土含水率观测、包气带负压观测等野外原位试验，结合气象资料，对包气带剖面流场特征进行分析，采用有限差分法对裸土蒸发强度进行计算。结果表明：依据包气带水分在垂向上迁移的不同状态，将裸土区包气带剖面划分为水分向上传输带和水分向下迁移带2个带；西北内陆干旱盆地裸土包气带极限蒸发深度为1．2 m；受外界蒸发能力和包气带向上输水能力交替控制作用，盆地内裸土蒸发出现在4月下半月至9月下半月，其中4月下半月至5月裸土蒸发强度最大，平均蒸发强度达0．56 mm/d；裸土蒸发强度平均仅占水面蒸发强度的3．5％，最大达6．7％。