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| DOI：10.13522/j.cnki.ggps.2019249 |
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| Spatiotemporal Variation in Depth of Groundwater Table and Water Salinity in Hetao Irrigation District Estimated Using Geostatistics |
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YAO Ling, YANG Yang, SUN Guanfang, ZHU Yan*, YANG Jinzhong
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The State Key Laboratory of Water Resource and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China
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| Abstract: |
| 【Background】Soil moisture and soil salt are important abiotic factors limiting crop growth in irrigated farmland. Soil salinization is the consequence of the interplay of soil water movement, depth of groundwater table and the concentration of soluble salts. Understanding spatiotemporal variation in depth and salinity of groundwater is hence critical to preventing soil salinization and improving groundwater management, especially for Hetao Irrigation district. With the quota of the Yellow River water for the district reduced and water-saving projects implemented over the recent years, the hydrological cycle and spatiotemporal distribution in groundwater table and salinity have both substantially changed.【Objective】The purpose of this paper is to analyze the spatiotemporal variation in groundwater table and salinity, as well as their determinants across the irrigation district.【Method】We used long-term experimental data measured from the district between 1998 to 2017, and analyzed them using GIS, geostatistics, descriptive statistics, semi-variogram and Kriging analysis.【Result】①The groundwater table and its spatial variability increased monotonically while the groundwater salinity and its spatial variability increased first followed by a decline during the studied period. The nugget coefficient of the groundwater table and water salinity was small, indicating that they were affected by environments more than by anthroponotic activities. The nugget coefficient of the groundwater salinity increased monotonically and its spatial structure consequently collapsed, alluding an increase in random variability caused by anthroponotic activities. The spatial autocorrelation distance of both groundwater table and water salinity increased steadily, implying an increase in spatial continuity of the groundwater. ②The groundwater was shallow along the Yellow River in the southwest of the district, with its depth in most areas < 2 m. In contrast, groundwater table in the northwest and northeast along the Wolf Mountains in the district was deep, with its depth >10 m in most areas. Groundwater salinity was mainly in the northwest and southeast, while salt content in the groundwater was low in the southwest and central pater of the district. ③Groundwater table rose and water salinity decreased in wet years due to increased recharge.【Conclusion】The groundwater table was relatively shallow in regions with high groundwater salinity, while deep in regions with low groundwater salinity. Spatial variation in groundwater salinity is associated with spatial variation in groundwater depth and the groundwater table can thus be used as an indicator to regulate soil salinization management. |
| Key words: Hetao Irrigation District; groundwater depth; groundwater salinity; geostatistics; GIS; spatial variation |
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