The Bureau of Reclamation, at the request of, and in collaboration with the Wyoming Game and Fish Department (WGF), has scheduled a flushing flow in the Big Horn River downstream of Boysen Dam. Flows were reduced from 800 cubic feet per second (cfs) to 700 cfs in February to conserve water to provide a flushing flow in late March, according to Wyoming Area Manager, John H. Lawson. The purpose of the flushing flow is to improve trout reproduction by flushing fine sediments from spawning gravels in the river. The flushing flow also improves insect production in the stream by opening up interstitial spaces between gravels and cobbles. The flushing flow is generally welcomed by anglers because it provides easier wading conditions. Following the flushing flow there is a reduction in floating algae. Flows in the river below Boysen Dam will fluctuate from 700 cfs to 5000 cfs during the flushing flow. On March 30 at 2:00 a.m., the release of water from Boysen Dam will be increased to 3000 cfs and further increased to 5000 cfs at approximately 7:15 a.m. for 10 hours before being reduced gradually back to 700 cfs by approximately noon on March 31, 2010.
This fun fact comes from an April 2003 Park Service report that states:Based on current data available, approximately 9,600 boats and 459 PWC use Bighorn Lake each year. All motorboats, including personal watercraft, are required to purchase permits. During the peak month of July, up to 77 boats and 5 PWC may use the reservoir per day.This is in stark contrast to the Montana Fish, Wildlife and Parks report Montana Statewide Angling Pressure Survey, 2007 which reported that 107,514 anglers used the river.
The average lake elevation for Bighorn Lake between the months of January and April is 3,606ft.The current elevation is: 3,629,48ft.