Assessing Groundwater Environment Changes in the Yongji Irrigation District under Rotational Well-canal Irrigation

Abstract

【Objective】 Yongji, located in the Hetao Irrigation district, has implemented a strategy of alternating between groundwater and surface water for irrigation to conserve water resources. This paper presents the outcomes of an experimental investigation into the repercussions of this practice on groundwater table change. 【Method】 The experiment was carried out in the Jingqu area of the Yongji irrigation district from 2018 to 2019. It involved measurement of the changes in groundwater depth, total salt content, total nitrogen, and phosphorus levels at 13 boreholes distributed across the region. We analyzed their spatial distribution and overall impact on groundwater dynamics. 【Result】 The alternating use of surface and groundwater for irrigation led to a reduction in the average groundwater depth by 0.15 meters. Simultaneously, it increased the average variation by 0.26 meters, and the coefficient of variation for groundwater depth by 1.13%, with the upper reaches of the irrigation district most affected. The decrease in irrigation area resulted in a reduction in areas with high salt content in groundwater, notably in the southeast of the upper reaches and northwest of the lower reaches, where the total salt content was reduced from 500 to 5 000 mg/L and 500 to 3 500 mg/L, respectively. Alternate irrigation also reduced the area with total nitrogen concentration exceeding 2 mg/L by an average of 14.38%, in addition to a marginal reduction in nitrogen and phosphorus in groundwater. The total nitrogen content in groundwater varied between 1 and 2 mg/L, while the area with total phosphorus content below 0.09 mg/L and 0.13 mg/L increased by 29.04% and 15.58%, respectively. 【Conclusion】 Alternate groundwater and surface water for irrigation can improve the utilization efficiency of groundwater and groundwater circulation. It also improved groundwater quality and alleviated the shortage of water resources in this region.

Keywords

• well canal rotation irrigation
• groundwater environment
• space distribution