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| DOI：10.13522/j.cnki.ggps.2019466 |
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| Using Water Surface Evaporation to Estimate Soil Surface Evaporation in Arid Regions in Central Ningxia |
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MA Ji’an, FENG Kepeng, LI Wangcheng, HAO Lu, LI Yukun, GAO Haiyan
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1. School of Civil and Hydraulic Engineering, Ningxia University, Yinchuan 750021, China; 2.Engineering Technology Research Center of Water-saving and Water Resource Regulation in Ningxia, Yinchuan 750021, China; 3. Engineering Research Center of Efficient Utilization of Modern Agricultural Water Resources in Arid Regions, Ministry of Education, Yinchuan 750021, China
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| Abstract: |
| 【Background】The arid regions in central Ningxia are characterized by scarce precipitation and high evaporation, with meteorological data from 1960 to 2016 showing an average annual precipitation of 183.1 mm compared to 2 000 mm of evaporation. Water-saving irrigation has been substantially improved in these regions, but water shortage is still the bottleneck restricting their agricultural production. Mulching the lands with gravels is a main cultivation method in these regions, and it is thus important to understand how the mulch alters the evaporation compared to that from bare soil, as soil evaporation is an important component in hydrological cycling and its calculation is not trivial and varies with disciplines.【Objective】 This paper aims to elucidate the relationship between soil surface evaporation and water surface evaporation, as well as the impact of soil water content in bare soil and the gravel-mulched soil on this relationship.【Method】 Outdoor experiments were conducted to analyze the relationship between soil surface evaporation and water surface evaporation using columns packed with both gravel-mulched soil and bare soil respectively. Soil evaporation was divided into different stages based on the ratio of soil surface evaporation to water surface evaporation at different times and water contents, and an empirical formula was derived to describe their relationships.【Result】 Evaporation from the bare soil could be divided into three stages while that from the gravel-mulched soil into two. The two critical ratios distinguishing the three evaporation stages in the bare soil were 0.209 6 g/g<θb1<0.214 8 g/g and 0.114 0 g/g<θb2<0.115 4 g/g respectively, while for evaporation from the gravel-mulched soil the critical ratio was 0.208 1 g/g<θg<0.214 7 g/g.【Conclusion】 The empirical formula derived based on the critical ratio was accurate to estimate soil surface evaporation from both the bare soil and the gravel-mulched soil. It can be used in agricultural water management and water resources planning to help design water-saving irrigation technologies and offer an alternative to study soil evaporation in these regions. |
| Key words: gravel-mulch; soil moisture; soil evaporation; water surface evaporation |
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