叶尔羌河流域潜水蒸发规律试验分析

ANALYSIS OF THE PHREATIC EVAPORATION IN YARKANT RIVER BASIN, XINJIANG

本文根据新疆叶尔羌河流域地下水均衡场的潜水蒸发试验资料，探讨了潜水蒸发的影响因素，对潜水蒸发量进行了公式拟合。结果表明，指数型公式、阿维里扬诺夫公式和清华公式比较适合于该地区潜水蒸发量的估算，幂函数型公式的拟合结果较差，简化的指数型公式有一定的适用范围。

As the main water consumption way in the vertical direction of the groundwater in arid area in Northwest China, phreatic evaporation is one of the main reason for water resources deficiency and soil salinization. The research on influence factor to phreatic evaporation and the calculation method is very important to the evaluation of groundwater resources. In order to find out the rule of phreatic evaporation and evaluate the groundwater resources exactly in Yarkant River Basin in Xinjiang, groundwater balance station was founded in Shache County.Phreatic water evaporation experiment has been carried out since 1993. The experiment includes 54 survey canister for 54 treatments with different soil textures and different phreatic water depth. The modified Mariotte Bottle is applied for water supply and groundwater level control in the canister. The infiltration water flows into the measuring glass through balance bottle. The phreatic evaporation of six different soil textures, including gravel, fine sand, fine sand soil, sand loam, light loam and mid loam in different phreatic depth is measured daily. Moreover, meteorological observation is carried out at the station. Based on the observation,factors influencing phreatic evaporation are discussed and empirical formulae for estimatingphreatic evaporation are regressed. It shows that the main factors influencing the phreatic evaporation are soil texture, phreatic water depth and the atmosphere evaporation capacity. The phreatic evaporation varies with the atmosphere evaPOration capacity. The smaller the phreatic water depth, the greater the influence of the atmosphere evaporation capacity to the phreatic evaporation. The phreatic evaporation decreases with the increase of phreatic depth. When the phreatic depth is larger than a critical value, the phreatic evaporation is close to zero. The phreatic evaporation also varies with the soil texture. Generally, when the phreatic depth is small, the phreatic evaporation is greater as the soil texture is coarser. However, when the phreatic depth is large, the phreatic evaporation is greater as the soil texture is finer. This is in accord with the variation of unsaturated water conductivity with the soil water content for different soil texture, which also reflects the effect of soil hydraulic properties to the phreatic evaporation. The regression to the phreatic evaporation or the phreatic evaporation coefficientshows that the results of Tsinghua Formula Lwith the form: E=Emax(1 -eηE20/E max)] is the best. But it requires more parameters that are not easy to obtain. The Exponential Type Formula (with the form: E/E20=ae-bH)and Formula [with the form: E/E20=a(1-H/Hmax]b) are suitable for the phreatic evaporation estimation of this region. The result of Power Type Formula (with the form: E/E20=aH-b)is the worst. The Simplified Exponential Type Formula (with the form: E =ae-bH)can only be used in a certain period. The coefficient a and b in the Exponential Type Formula from regression is 0. 62, 1. 55 (gravel),0. 62, 1. 5 (fine sand), 0. 62, 0. 8 (fine sand soil), 0. 62, 1. 1 (sand loam),0. 62, 0. 8 (light loam) and 0. 62,0. 9 (mid loam). The coefficient a, b and Hmax in the Formula is 0. 62, 2.2, 2.0 (gravel),0. 62, 2. 6, 2. 58 (fine sand),0. 62, 2. 8, 4. 5 (fine sand soil), 0. 62, 3.1,3. 5 (sand loam), 0. 62, 3. 2, 5.0 (light loam) and 0. 62, 3. 6, 5. 5 (mid loam).