黄土高原半干旱区降雨入渗试验研究

黄土高原地区地下水资源缺乏,降雨是土壤水的唯一补给来源。为研究降雨补给地下水过程,在黄土丘陵半干旱区的米脂试验站,对野外10 m土柱土壤水分进行了定位观测,分析自然降雨下土壤水分入渗深度和补给量。结果表明:自动监测显示单次降雨量为5.2 mm(小雨)时,11 h后入渗达到最大深度0.3 m,此深度以下几乎没有变化;单次降雨量为15.8 mm(中雨)时,4 d内影响深度可达0.6 m;单次降雨量为33.6 mm(大雨)时,8 d内1.2 m处土壤含水量增长明显,1.4 m以下没有变化。水分循环主要在0.8 m以内的蒸发带,该层土壤水分易被蒸发,0.8 m以下随着深度增加,土体含水率变化逐渐滞后,增幅逐渐减小。受多种因素影响,入渗过程持续时间不一。覆盖处理观测期土壤水分补给量显示:覆膜石子树枝裸地,补给量与降雨量呈线性关系,覆膜补给量上升最大。

Experimental study on rainfall infiltration in semiarid region of the Loess Plateau

The water resource has becoming limited in the Loess Plateau area ,and rainfall is the only supply for soil water .In order to study the process of groundwater recharging ,regional observation was conducted on soil water of a soil column at 10m depth in Mizhi experimental station .Infiltration depth and amount of groundwater feed were analyzed .The results showed that that by automatic monitoring , the moisture content of soil layers within 0 .3 m changed obviously eleven hours after a single precipitation reached 5 .2 mm (light rain ) ,while that below 0 .3 m exhibited almost no changes .When a single precipitation was 15 .8 mm (moderate rain ) ,within four days ,the resulting depth could be up to 0 .6 m .When a single precipitation was 33 .6 mm (heavy rain ) ,the moisture content at 1 .2 m soil layer changed ob-viously and that at 1 .4 m became slightly increased in eight days .Water cycle was mainly conducted over 0 .8 m of the evaporation zone where soil moisture became evaporated easily .With the increase of soil depth below 0 .8 m ,variations of moisture content were small and the amplitude level gradually went decreased .Due to influences from multiple factors , the durations of infiltration varied .During the observation period ,soil moisture recharging by cover treatment showed that the resulting effects were in the order of the follows:plastic mulching>gravel>branch>bareland .The recharging under each treatment had a linear correlation with rainfall amount .The recharging reached maximum with plastic mulching .