河套灌区地下水适宜埋深、节水阈值、水盐平衡探讨

Discussion on Suitable Depth of Groundwater Level, Water-saving Threshold and Water-salt Balance in Hetao Irrigation District

【目的】分析探讨河套灌区当前地下水适宜埋深、节水阈值和水盐平衡状况。【方法】采用数理统计的方法,对河套灌区1998—2018年的引黄用水量、地下水埋深、水盐平衡等资料进行统计分析。【结果】2016—2018年,灌区由黄河水带来的盐分每年平均约254万t;排入乌梁素海的盐份年均约106万t,每年约有148万t盐分滞留在灌区内,灌区土壤仍然处于连续积盐状态。由于引入和排出大量的生态水,乌梁素海排入黄河的盐分年均188万t,属于脱盐状态,乌梁素海水质持续改善。河套灌区地下水适宜开采量约为3.2亿~3.6亿m3/a,灌区近年地下水实际开采量2016年为2.1亿m3,2017年为2.4亿m3,2018年为2.15亿m3,目前灌区还有约1.5亿m3的地下水开采潜力。【结论】河套灌区目前地下水年均适宜埋深为1.8~2.5 m,认为灌区农业引黄水量下限(节水阈值)约为40亿m3,每年还应该引入3亿~4亿m3的生态用水,用于维持乌梁素海和灌区湖泊湿地的的生态环境。

【Objective】The purpose of this paper is to discuss the current suitable depth of groundwater level,water-saving threshold and water-salt balance in Hetao Irrigation District.【Method】Mathematical statistics method was applied to analyze the water consumption,depth of groundwater level,water-salt balance and other data of Hetao Irrigation District from 1998 to 2018.【Result】From 2016 to 2018,about 2.54 million tons salt brought to Hetao Irrigation District from Yellow River water on annual average;About 1.06 million tons salt was discharged into the Wuliangsuhai Sea on annual average,and about 1.48 million tons of salt remain in Hetao Irrigation District every year,and thus the soil was still in a state of continuous salt accumulation.Due to the introduction and discharge of a large amount of ecological water,1.88 million tons of salt discharged into the Yellow River from Wuliangsuhai Sea on annual average,which was in the state of desalination,and therefore the water quality of Wuliangsuhai Sea continues to improve.The suitable exploitation amount of groundwater was about 3.2×109~3.6×109 m3 every year in Hetao Irrigation District.In recent years,the actual exploitation amount of groundwater in Hetao Irrigation District was 2.1×109 m3 in 2016,2.4×109 m3 in 2017,2.15×109 m3 in 2018.The current groundwater exploitation potential was about 1.5×109 m3 in Hetao Irrigation District.【Conclusion】The suitable annual average depth of groundwater level was 1.8~2.5 m in Hetao Irrigation District.We considered that the lower limit(water-saving threshold)of agricultural water diversion in Hetao Irrigation District was about 4×109 m3,and3×109~4×109 m3 of ecological water should be introduced every year to maintain the ecological environment of Wuliangsuhai Sea,lakes and wetlands in Hetao Irrigation District.