Drought has also affected the dam's operation. No water was permitted to flow over the dam in 1986 due to drought. In 1992, water flowed over the dam's crest on only a single day. In wetter years, water flows over the dam almost continuously. A severe drought struck the state of Montana beginning in 1999. By May 2004, the dam was permitting only to per second downriver. These flows were well below the per second needed to keep the fishery healthy. The low water flows, coupled with whirling disease, led to a 40 percent drop in big fish (those over in length) as well as lower overall numbers of fish immediately below the dam. A 2005 proposal by the managers of the Helena National Forest to draw down Holter Lake by in August 2005 in order to repair Coulter Campground near the Gates of the Mountains had fishermen and recreational outfitters angry due to the likely side-effects on the downstream fishery. But a 2006 study by state wildlife biologists found that, although there had been a slight decline in the number of all fish as well as the sizes of all fish since the sport fish population peaked in 1999, those declines were slight compared to what had been predicted. A 2006-2007 survey of burbot and stonecats in the Missouri River immediately below Holter Dam found four times as many burbot as expected. Heavy snowpack and spring rains in 2008, however, forced dam operators to increase the flow to per second. By June, flows increased to per second, permitting a flush of the river. Flows stayed double their typical flow rates even in July 2008.