One hundred eighty miles below Alcova Dam and 25 miles below Glendo Dam, the Guernsey Dam controls river flow. Water released from Pathfinder Reservoir can be stored and released to fit varying irrigation demands. Water is released through the Guernsey Powerplant.
Guernsey Dam is in a rocky canyon 2 miles upstream from Guernsey, Wyo. It is a diaphragm-type embankment of sluiced clay, sand and gravel that forms an impervious core. Its slopes are protected by a thick layer of rock riprap. The structural height of the dam is 135 feet. The original capacity of the reservoir was 73,810 acre-feet, but this has been greatly reduced by silt deposits. The powerplant is on the right bank below the dam and has two 2,400-kilowatt generators. Power is transmitted to towns and industries down the valley over project and other interconnected transmission system lines.