Calculating Groundwater Evaporation Based on Meteorological Data and Groundwater Table Depth

Abstract

【Objective】 Groundwater evaporation is a main component in the hydrological cycle and is modulated by many biotic and abiotic factors. The purpose of this paper is to estimate groundwater evaporation through different soils using meteorological data and groundwater table depth. 【Method】 The estimate model was derived based on groundwater evaporation and meteorological data measured from Wudaogou Hydrological Experimental Station in Huaibei plain. Two soils, lime concretion black soil and yellow fluvo-aquic soil, were used in the experiment, and the surfaces of the two soils were both kept bare. The Mann-Kendall method was used to examine the inter-annual variation in groundwater evaporation from the two soils using SPSS statistical software. The changes in groundwater evaporation with meteorological factors and the groundwater depth were analysed, from which we derive multiple regression models. 【Result】 The impact of the meteorological data and groundwater depth on groundwater evaporation depended on soil types. For the lime concretion black soil, the impact of meteorological data was ranked in the order of soil surface temperature > average ambient air temperature> rainfall>length of sunshine, while for the yellow fluvo-aquic soil, they were ranked in the order of surface temperature>average annual temperature>rainfall>relative humidity> period of sunshine. For both soils, the regression model using meteorological data can accurately predict groundwater evaporation with R2>0.7. Nonlinear fitting showed that for the lime concretion black soil, the groundwater evaporation changed with groundwater depth in a power-law function with R2>0.8 in spring, autumn and winter with associated critical groundwater depth (below which the evaporation reduces to zero) was 1.55 m, 1.01 m and 1.13 m respectively. Yet in summer, their relationship was best described by the Weibull function, with R2=0.99 and critical groundwater depth being 1.78 m. For the yellow fluvo-aquic soil, the exponential function described the change in groundwater evaporation with the groundwater depth better, with R2>0.93 and the critical groundwater depth varying from 2.3 to 2.9 m. 【Conclusion】 Groundwater evaporation was affected by both groundwater depth and meteorological factors, but their relationships varied with seasons and soil types. This paper presented models describing their relationships.

Keywords

• groundwater evaporation
• meteorological factors
• groundwater depth
• bare soil surface
• huaibei plain