Denver Water is once again closing a popular recreation area in the Denver suburbs to finish a dredging project. Waterton Canyon was reopened March 1 after being closed since July 2010. Denver Water needed to dredge the Strontia Springs Reservoir to clear sediment that built up after the 1996 Buffalo Creek wildfire and 2002 Hayman wildfire.The fires stripped away vegetation and triggered erosion. That debris makes it much more expensive and much more difficult to treat water. The three-week closure that begins April 1 will allow contractors to remove a 75-ton dredge.