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| DOI：10.13522/j.cnki.ggps.20180657 |
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| Using Bromide Tracer Method to Analyze the Evaporation Rule of Phreatic Water in Arid Area |
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TAN Chang, WU Jingwei, WANG Changshu, WANG Ke, YANG Liqing, CHANG Zhifu
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1. The State Key Laboratory of Water Resource and Hydropower Engineering Science,Wuhan University, Wuhan 430072, China;2. Yichang Irrigation Bureau of Hetao, Inner Mongolia, Wuyuan 015100, China
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| Abstract: |
| 【Objective】 The objective of this study is to quantitatively analyze the rule of phreatic evaporation in arid area. 【Method】 Bromide tracer experiments were conducted at six field sites in the fallow areas of Hetao Irrigation District in attempts to estimate phreatic evaporation according to the peak of tracer's concentration in soil profile. The results of bromide tracer experiments were compared with the water balance method and empirical equations methods. Meanwhile, the observation of soil water content and soil salt content at different soil depth for each experimental sites were collected to illustrate its effect on phreatic evaporation. 【Result】 The accumulative phreatic evaporation estimated from the tracer experiment was 35.20 mm with the average evaporation rate being 0.28 for the period of 6 July to 18 August. The result was close to 32.29 mm that calculated from water balance analysis and the correlation coefficient between the two was 0.96. Considering the strong spatial heterogeneity of soil properties in study sites and the lack of hydrogeological data in arid area, results generated from water balance analysis and empirical equation methods were less reliable since the parameters were hard to be determined with limited data. Overall, the bromide tracer method was a simple and convenient way for the practical application and more reasonable than the two other traditional methods. The accumulative phreatic evaporation decreased as the clay content of soil increased with the correlation coefficient of 0.80, especially when there was a clay-layered soil, the rate of phreatic evaporation would drop significantly. 【Conclusion】 The soil salt content increased with the increase of phreatic evaporation, indicating that the high evaporation demand is the driving force for water and salt exchange from the croplands to the fallow areas, which directly affects the water cycle process in irrigation areas. |
| Key words: bromide tracer method; phreatic evaporation; soil properties; arid area |
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