《水经注·卷二十二》
洧水又往东南流，与龙渊水汇合。龙渊水发源于长社县西北，有一条旧沟，上口承接洧水，水大时就与龙渊相通，水浅时沟渠就断流。
洧水又东南与龙渊水合，水出长社县西北，有故沟，上承洧水，水盛则通注龙渊，水减则律渠辍流。
The Yishui River flows southeast again, merging with the Longyuan River. The Longyuan River originates from the northwest of Changshe County, and there is an old ditch, the opening of which connects to the Yishui River. When the water level is high, it merges with Longyuan, and when the water level is low, the ditch is closed.