Changqiao Sea is located in Mengzi City, adjacent to Datun Sea, just on the Tropic of Cancer. The Yi language name is "矣坡黑", which means "the sea with springs at the bottom of the lake". It is a faulted basin from Mengzi. The lake formed by the inland surface water converging towards the depression is part of the remnants of the ancient lake. The Changqiao Lake is 1284 meters above sea level, with a reservoir area of 1167.73 hectares, a maximum water depth of 7 meters, an average water depth of 4 meters, a shoreline of 9.5 kilometers, and a normal water storage capacity of 45 million cubic meters. In addition to receiving water from Dahonggou, Sarah River, and Lijiang River, Changqiao Sea also has three dikes in the east, west, and south, and the Nanxi River, a tributary of the Red River, is injected. The runoff area is 167 square kilometers, and the excess water is discharged. After going to Datunhai, in the wet season, the discharge flows eastward through Caoba and then turns to the Shadian River to join the Lujiang River and into the Nanpan River. It can be said that it is a red soil plateau lake connecting the Red River system and the Pearl River system.