中国西北干旱区过度灌溉绿洲的水分收支特征研究

基于水分收支平衡原理, 观测2012年生长季张掖绿洲的水分收支分量动态特征, 探究灌溉对绿洲水分收支的影响。结果表明: 1) 无降水及灌溉时, 绿洲内40~100 cm深度的土壤含水量高 0~20 cm的土壤, 强降水事件对0~20 cm的土壤含水量影响较大, 而灌溉事件对 0~100 cm的土壤含水量有明显影响; 2) 无降水及灌溉时, 绿洲的日均蒸散发(ET)为2.83 mm/d, 降水事件后3日蒸散发量为降水之前的 1.16倍, 灌溉事件之后2日蒸散速率为灌溉之前的1.88倍, 说明灌溉对绿洲的蒸散发影响更为显著; 3) 绿洲生长季水分收支收入项(降水和灌溉, P+I)中, 灌溉占89.7%, 水分支出项主要为深层渗漏(DP), DP/(P+I)为81%; 4) 2012年生长季绿洲灌溉需水量为213 mm, 实际灌溉量比灌溉需水量多出474 mm, 远远超出所需, 水资源浪费严重。

Water Budget Characteristics of Over-Irrigated Oasisin Arid Region of Northwest China

Based on the water balance equation, a field experiment was carried out to observe the dynamic characteristic of volumetric soil water content during growing season of 2012 and to explore the impact of irrigation on the oasis water budget. The results showed that in the Zhangye oasis, the volumetric soil water content at the depth of 40–60 cm was higher than that at the depth of 0–20 cm during days without precipitation and irrigation. Heavy precipitation has an obvious impact on the volumetric soil water content at the depth of 0–20 cm while irrigation has an obvious impact at the depth of 0–100 cm. The daily evapotranspiration (ET) was 2.83 mm/d during days without precipitation and irrigation. The ET volume of the third day after precipitation increased by 16% compared to the ET volume before precipitation. The ET rate of the second day after irrigation was observed with an increase of 88% compared to the ET rate before irrigation, indicating that the impact of irrigation on ET was more significant than that of precipitation. The primary incomings of the water budget in the oasis was irrigation, which accounted for 89.7% of the total incomings. The main outgoings of the water budget in the oasis was deep percolation (DP), which accounted for 81% of the total outgoings. The irrigation water requirement was only 213 mm during the growing season of 2012, but the real irrigation volume exceeded the irrigation water requirement by 474 mm. Excessive deep percolation and serious water wastage was obvious during growing season due to the heavy irrigation.