Sancha-hu (Lake Sancha) is a man-made lake. The construction work was designed by the Sichuan Survey and Design Institute for Water Resources and Electric Power, and implemented by the government of Jianyang County. The work was started in March 1975, and completed in February 1977.

The site of the reservoir is a transitional zone between Longyuan Mountains and the hilly area covered by terra rossa which belongs to an inland lake sedimentary phase of Upper Jurrasic and Cretaceous Periods. The surrounding hills have gentle slopes and are made of relatively hard rocks. The quality of air and water comes up to No. 1 grade of National Environmental Standards.

The purpose of damming was to store water for irrigating farmlands, now amounting to 39,700 hectares. Meanwhile fish culture and uses for recreation/tourism have been developed. The reservoir with its natural scenic beauty and nearby historic sites is now a famous touristic site in the western part of Sichuan Basin (Q).