ATLANTA (AP) — Plumbing problems at the dam holding back the second-largest reservoir in the U.S. are spurring concerns about future water delivery issues to Southwestern states supplied by the Colorado River.

Federal officials recently reported damage to four tubes known as “river outlet works” at Glen Canyon Dam on the Utah-Arizona border. The dam is responsible for generating hydropower and releasing water stored in Lake Powell downstream to California, Arizona, Nevada and eventually Mexico.

The U.S. Bureau of Reclamation, which operates the major dams in the Colorado River system, is evaluating issues related to Glen Canyon Dam when Lake Powell reaches low levels. Those issues include problems with the four tubes such as sedimentation and cavitation — when tiny air bubbles develop while water passes through plumbing. Cavitation can cause tears in metal and other mechanical damage.