Lower end of Holter Reservoir may close for firefighting efforts Inciweb and last updated 2021-07-27 18:40:11-04 HELENA â Montana Fish, Wildlife and Parks (FWP) is warning the public the lower end of Holter Reservoir may be closed this week to allow fire-fighting resources access to the water. People should be aware that if a closure is implemented, FWP wardens, along with other law enforcement agencies, will be contacting boaters and other recreationists using the reservoir to leave immediately. Boating activities will be restricted from all private and public launch sites and boaters will not be allowed to travel on the water once the closure is initiated.