Sitting at the forks of the Lehigh River, Francis E. Walter Dam is a behemoth capable of harnessing the power of a river, then releasing it on demand for the enjoyment of white water rafters and kayakers.

And while it's become a big part of the area's tourist draw, white-water rafting is only a secondary function of the 55-year-old dam.The primary function of the Francis E. Walter Dam is flood control, according to engineer George Sauls.Up until his retirement earlier this year, Sauls oversaw the five dams in the Army Corps of Engineers' Philadelphia District. That includes Walter, Beltzville and Blue Marsh Lake in Berks County.Over its 50 years in existence, the dam is estimated to have saved more than $200 million in flood damage.All the runoff water from a 288-square mile area, the headwaters of the Lehigh, ends up passing through in the dam at some point. Beltzville is located on a tributary of the Lehigh and drains about the same area that Walter does.Compared to other dams like Beltzville, the amount of water kept in Walter is much lower - roughly 18 percent of its total capacity.That's because whenever a storm is forecast, they're required to dump whatever water is inside the dam down the Lehigh to increase the dam's capacity.The highest water level ever recorded at the dam was during the June 2006 flood, when the lake hit roughly 85 percent of its capacity. The water was 8 feet from the spillway crest at that time.But Sauls said that the water level would have to rise significantly higher in order to "top the dam.""It's built to withstand the probable maximum flood. It's the largest possible flood. Noah's Ark. If you wanted to put a frequency on it, it would be in the 10,000-15,000 year range," Sauls said.Even so, Sauls makes it clear that the dam's job is to reduce floods, not prevent them.In instances of extreme drought, the dam will be called upon to hold water for the Delaware River Basin Commission."Over the years, it's been operated for a number of different purposes, but it was originally built for flood control," Sauls said.The dam is controlled by massive electric flood gates located at the base of the 150-foot tower. The three staff members at the dam must go into the tower each day to adjust the dam releases, which are adjusted nearly every day.Proposed in 1942 and built in 1960, Walter is named for a congressman from Easton.Sauls said that the dam was probably conceived after a lethal flood struck the Lehigh Valley in 1942. The later, more powerful 1955 flood probably just confirmed the need for it, Sauls said. The construction road along the upstream side of the dam was supposed to be demolished after the dam was completed. However, it saved what would have been a 17-mile detour around the dam for locals, so it was kept.In the early '80s, DRBC proposed using Walter as a reservoir, and significantly increasing the amount of water it stored.In preparation for the project, a new road was built along the top of the dam, offering one of the most dramatic views in the area, and preserving the shortcut once the old road was flooded. The Army Corps was not interested, and the project failed. But residents get the benefit of the road.White-water rafting was initially a novel benefit of the dam. Up until the mid-80s, there were five dam releases per year. Then the Army Corps added recreation as a stated purpose of the dam.Today and Sunday, they have water releases for the benefit of fishermen downstream, as well as rafters.The morning of a dam release, at 1 a.m., they open the electric-powered gates at the base of the dam, releasing the water. It takes several hours for the water to reach Jim Thorpe, where it makes for ideal rafting conditions.As the year goes on, the plan is modified based on the amount of rainfall the area receives.There are competing interests in the dam. Fishermen want a steady flow of cold water to help promote the trout population. Whitewater rafting outfitters would prefer big, explosive releases that make their customers happy.Both sides would like to see the dam store more water, but as long as its stated purpose is flood control, that won't happen."We've prioritized things to the point that I think, the competing interests are at equal levels of dissatisfaction," Sauls said.