Castro Reservoir, located in Malheur County, Oregon, is a gravity dam constructed in 1982 by the Bureau of Land Management for water supply purposes. The reservoir has a maximum storage capacity of 107 acre-feet and a normal storage capacity of 69 acre-feet, serving as a vital source of water for the surrounding area. With a surface area of 12.6 square acres, the reservoir is fed by Spring Branch Creek and has a maximum discharge of 5295 cubic feet per second.

The dam stands at a hydraulic height of 19 feet and a structural height of 22 feet, with a length of 400 feet. The spillway, which is uncontrolled, is 40 feet wide. Despite being classified as having a low hazard potential, the reservoir is subject to moderate risk, with a risk assessment rating of 3. The last inspection of the dam was conducted in September 2018, with an inspection frequency of every 5 years. Overall, Castro Reservoir plays a crucial role in water resource management in the region, providing essential water supply services while maintaining a relatively low hazard potential.