引黄调水对汾河受水区水环境的影响

引黄入晋工程缓解了太原市水短缺问题。然而,近年来上游黄河水出现较严重污染。引黄调水对汾河受水区的影响尚不明确。论文基于连续观测和采样,分析了受水区河水、地下水水文过程、理化性质、主要离子、典型污染物邻苯二甲酸二丁酯以及大肠杆菌的含量和变化。结果表明：受水河流和河岸带地下水受引黄影响十分明显,含盐量和有机物含量显著增加,水环境整体退化;引黄导致汾河雨季高水位而旱季低水位的水文过程反转,且整个水文年内河水以饱和输水的方式补给浅层含水层,水位埋深变浅;汛期河谷发生洪水的风险大大增加;引黄导致汾河水电导率增大两倍左右,且河水由Ca-HCO₃型变为Na-Cl·SO₄型,而溶解有机碳含量增高约26%,UV₂₅₄含量增大约24%;引水暂停期汾河水水化学特征趋于恢复,而河岸带地下水水化学特征未能恢复。长期来看,若引黄调水持续向河谷地下水输入大量Na⁺和Cl^-等,且地下水埋深持续保持在较浅的范围,可能造成土壤盐碱化、植被退化和生态环境恶化等更加严重的后果。

Impacts of Water Transfer from the Yellow River on Water Environment in the Receiving Area of the Fenhe River

The project of water transfer from the Yellow River to the Fenhe River launched in 2003 relieved water shortage in Taiyuan. However, the impacts of the polluted Yellow River on the water environment of upper reach area of the Fenhe River were seldom reported. Based on long term observations and samplings, physicochemical properties, major ions, the typical pollutant DBP and Escherichia coli in the receiving river were measured. Results show water transfer imposed great impacts on hydrologic processes and water environment of river and groundwater in the receiving area. The hydrological process of high stage in rainy seasons and low stage in dry seasons was inversed by the Yellow River water transfer project. High water stage in dry seasons was due to huge amount of water transfer, and low stage in rainy seasons was owing to the temporary stop of the water transfer. At the same time, the accelerated velocity of the receiving river increased the river bottom erosion, which could enhance the exchange between the river and the shallow groundwater in the riparian zone. The river water recharged groundwater in saturated condition during the whole hydrologic year, and the water table depth of shallow groundwater was significantly decreased. The risk of flooding might greatly increase. Water environmental degradation was also triggered by the water transfer. The dissolved salts and organic contaminant contents in the receiving river and the shallow groundwater increased. EC value of the Fenhe River was doubled with the geochemical face of the river water changed from Ca-HCO₃ to Na-Cl·SO₄ by the water transfer. Also, DOC and UV₂₅₄ of the river water were increased by 26% and 24%, respectively. When water transfer stopped periodically, the hydro-chemical features of the receiving river recovered. However, the obvious impacts of water transfer on the shallow groundwater in the riparian zone remained. In the long term, excessive Na⁺ and Cl^- imported by the water transfer would make the environment of the receiving area worse, and the elevated evaporation rate of soil moisture and the shallow water table depth would lead to the occurrence of soil salting and vegetation degradation.