Yanhe spring karst water system is one of the famous springs in North China.

山西省延河泉岩溶水系统是我国北方岩溶大泉之一。

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With the increase of petroleum resource exploitation in Northern Shaanxi during recent decades, the quality of surface water of Yanhe River and Qingjianhe River is affected seriously.

近几十年来陕北地区油气大规模的开采，对延河和清涧河流域地表水水质状况造成严重影响。

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