库尔勒地区不同下垫面潜水蒸发昼夜变化特性研究

Diurnal variation characteristics of groundwater evaporation with different underlying surfaces in Korla

为研究新疆地区的潜水蒸发特性,开展了裸地（埋深1.0 m、1.5 m和2.0 m）、覆膜无作物（开孔率0.78%、2.4%和5.0%）以及种植棉花（埋深1.0 m、1.5 m和2.0 m）等三种下垫面条件的潜水蒸发试验,分别研究了昼夜、日间及夜间变化动态。研究表明,有作物比无作物潜水蒸发系数大,且随埋深的增加,两者潜水蒸发系数差异性减弱;三种下垫面条件共9种处理均表现为潜水夜间蒸发补给量大于白天蒸发补给量,且地下水埋深越大,裸地夜间潜水消耗与白天潜水消耗的比值有所降低,棉花地则是呈增加趋势,这与棉花蒸腾强度的昼夜变化不同有关。进一步分析表明,无作物种植时,潜水蒸发的日变化波动幅度较大,潜水蒸发主要消耗时段为2∶00~10∶00和18∶00~22∶00;有作物种植时,潜水蒸发的日变化较为稳定,其无明显主要消耗时段,只是在昼夜交替时（20∶00左右）发生较大幅度变化;白天尤其是午后,因强烈的太阳辐射使得土壤输水能力不能满足大气蒸发需求而导致毛管断裂,潜水蒸发量明显降低,平均降低0.66mm.h-1;夜间土壤的输水能力大于蒸发能力而使毛管恢复连通,从而促使潜水蒸发有所增强,平均增加0.26mm.h-1。

In attempt to study diurnal variation characteristics of groundwater evaporation with different underlying surfaces in Korla area,three kinds of underlying surfaces,bare soil（buried depths are 1.0 m,1.5 m and 2.0 m）,film mulching without crop（open hole ratios are 0.78%,2.4% and 5.0%） and cotton（buried depths are 1.0 m,1.5 m and 2.0 m）,were tested in this paper.The results showed that groundwater evaporation coefficient with crop was higher than that without crop,and difference between them decreased gradually with increase of buried depth.All the test results indicated that groundwater evaporation was higher in nighttime than in daytime.The ratio of bare soil groundwater consumption between nighttime and daytime was reduced,but ratio for cotton was increased with increase of groundwater depth,which may have nothing to do with difference of diurnal variations of cotton transpiration intensity.Further study showed that without crop planted,diurnal variations range of groundwater evaporation was bigger,and major groundwater consumption periods were 8∶00~10∶00,18∶00~22∶00 and 2∶00~6∶00;however,groundwater evaporation intensity for treatments with crop planted was stable and had no obvious consumption periods.It only had a significant change at about 20∶00.Daily variation of groundwater evaporation showed more obvious fluctuation in the treatment without crop planted than in the treatment with crop planted.During daytime,especially in the afternoon,groundwater evaporation intensity was significantly reduced（by 0.66 mm·h-1）,which was caused by less of water transport rate in soil than atmospheric evaporation capacity.In nighttime,groundwater evaporation intensity was increased by 0.26 mm·h-1,which was mainly due to the fact that water transport rate in soil was bigger than the atmospheric evaporation capacity.