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| DOI：10.13522/j.cnki.ggps.2020355 |
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| Effects of Salt Content on Evaporation from Seasonally Frozen Soil: Experimental Measurement and Numerical Simulations |
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MAO Jun, WU Jingwei, LIU Yawen, WU Mousong
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1. State Key Laboratory of Water Resource and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China; 2. International Institute for Earth System Science, Nanjing University, Nanjing 210046, China
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| Abstract: |
| 【Background】Seasonally frozen soils are a widely distributed land resource in China, and sustaining their agricultural production is essential to meet the increased demand of the growing population for foods. Hetao irrigation district in Inner Mongolia is one of three major irrigation districts located in seasonally frozen regions, and its agricultural production is constrained by soil salinization and water shortage. As soil salinity and soil evaporation are interconnected, understanding the changes in evaporation from soils with different salinity is important for improving water and salinity management in seasonally frozen soils.【Objective】The purpose of this paper is to evaluate the impact of salt content on evaporation from soils subject to freezing-thawing cycles. 【Method】Soil columns packed by soil with salt content 7.80 g/kg (B1) and 41.16 g/kg (B2), respectively, were used in the experiments conducted in Inner Mongolia. Evaporation from the columns under a thawing-freezing process was measured, from which a numerical model, considering the effects of salt contents on soil surface impedance, was developed to calculate the evaporation. We calibrated and validated the model against the experimental data and compared it with the SHAW model first, and then used it to simulate evaporation under freezing-thawing processes from soils with salt contents ranging from 0 to 50g/kg.【Result】The impact of salt content on evaporation was noticeable, especially at the beginning of the freezing and thawing processes, with their associated average evaporation from the B1 treatment being1.5 times and 1.8 times that of the B2 treatment, respectively. Compared with the SHAW model, the numerical model simulated the evaporation process reasonably well and was more suitable for seasonally frozen soil with salinization. During the freezing-thawing process, the evaporation from soil increased first followed by a decline as the salt content increased. When the salt content was 15 g/kg, the maximum evaporation was 136.3 mm. Compared to soil without salinization, increasing salt content from 2.5 g/kg to 20 g/kg increased soil evaporation from 1.09% to 86.46%. In contrast, increasing salt content from 20 g/kg to 50 g/kg reduced the evaporation gradually by up to 42.55%.【Conclusion】Salt content has a great impact on evaporation from seasonally freezing-thawing saline soil. With salt content increasing, the evaporation increased first followed by a decline. The proposed numerical model considering the effects of salt improved accuracy of the predicted evaporation. Our results have implications for improving our understanding of the mechanisms underlying evaporation from seasonally frozen salt-affected soils and provide methods for simulating soil and water dynamics in these regions. |
| Key words: soil salt content; seasonally freezing-thawing; soil evaporation; numerical simulation |
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