Fig. 1

Gates near both the top and the bottom of the reservoir dam of the Xiaoliandi Reservoir Lake were opened when a disastrous flood of the Yellow River threatened to overflow the dam. Huge water masses could thus be released. The water released from the top part of the lake, flowing through the upper gates of the dam, was clean. Due to mixing with air, this water was bright white. In contrast, the water released through the gates near the bottom had a brown color. This water was sediment-laden because a long-lived hyperpycnal flow eroded and whirled up much sediment from the reservoir’s bottom. (From Yang et al. 2018, after https://www.quanjing.com/imgbuy/QJ8103941831.html)