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| DOI：10.13522/j.cnki.ggps.2021621 |
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| Geostatistical Analysis of Spatial Variability of Soil Water and Salt in Hetao Irrigation District |
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LIU Yan’nan, SUN Guanfang, MAO Wei, CHENG Xiaoyao, ZHU Yan, YANG Jinzhong
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1. The State Key Laboratory of Water Resource and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China;
2. Institute of Soil and Water Conservation, Northwest Agriculture and Forestry University, Yangling 712100, China;
3. Zhongnan Municipal Administration General Design Institute Co. Ltd., China Municipal Engineering, Wuhan 430101, China
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| Abstract: |
| 【Background and objective】Soil salinity is an abiotic stress affecting agricultural production worldwide, especially in countries in arid and semi-arid regions. Soil salinity is closely correlated to soil water, both varying erratically over space and time. Understanding their spatial variability is essential to improving water use efficiency and alleviating soil salinization. This paper aims to analyze the spatial variability of soil water and salt at different soil depths, their relationship in Hetao Irrigation District, as well as their dependence on groundwater depth and salinity.【Method】The study site is at Longsheng, a typical well-canal conjunctive irrigation area in the irrigation district. Soils were sampled from the root zone (0~60 cm), subsoil (60~120 cm) and deep soil (120~180 cm), and the moisture and salt contents in each sample were measured using standard laboratory methods. Their spatial variations were analyzed using classical statistical and geostatistical methods. The relationship between groundwater and soil salinity was calculated using the Pearson correlation analysis.【Result】① The averaged soil water content at different soil depths were ranked in the order of 0~60 cm<60~120 cm<120~180 cm, while the averaged soil salt content were ranked in the order of 0~60 cm>60~120 cm>120~180 cm. The variation coefficient and nugget coefficient of soil water and salt content decreased monotonically with soil depth, while their spatial autocorrelation distance increases monotonically with the depth. Soil water and salt content in the root zone showed moderate spatial autocorrelation, while in deep soil they showed a strong spatial autocorrelation. ② The variation coefficient and nugget coefficient of soil water in each soil layer are smaller than that of soil salt, while its variation range is larger than that of soil salt; there was a strong negative correlation between them. ③ Soil salt in each soil layer is exponentially related to groundwater depth, but is a power-law function of groundwater salinity. When the groundwater depth is greater than 2.5 m, the soil salt content is low and the soil salinity only slightly changes with groundwater depth.【Conclusion】Salt accumulates mainly in the root zone and its spatial distribution is closely related to soil water content. Groundwater depth is the major controlling factor of soil salinity, and to reduce the risk of soil salinity, the groundwater depth should be controlled below the depth of 2.5 m. |
| Key words: Hetao Irrigation District; soil water and salt; geostatistics; spatial variation; groundwater environment |
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