The Fill the Lake Act directs the Secretary of the Interior to maintain Flathead Lake in Montana at specific water levels during the summer months, between June 15 and September 15 each year. The law requires the lake to be kept at a minimum elevation of 2892 feet above sea level by releasing water from Hungry Horse Reservoir upstream, and prevents the lake from exceeding 2893 feet by releasing excess water downstream. This one-foot operational range ensures the lake remains at nearly full capacity during peak summer recreation season. The legislation affects water management operations in northwestern Montana and impacts how federal agencies manage the Hungry Horse Dam and reservoir system. No specific funding amount or implementation timeline beyond the seasonal dates is specified in the bill.