The office of the Washington State Climatologist is monitoring two rain gauges near the Howard Hanson Dam, monitoring in near-real-time how much water is feeding into the reservoir.
Heavy rainfall in January 2009 -- when the reservoir went from nearly-empty to nearly-full in 48 hours -- damaged an earthen abutment adjacent to the dam. The Army Corps of Engineers and contractors have been working to strengthen the dam by injecting concrete-like grout into the abutment to strengthen it. Still, the Corps has repeatedly said that it may be necessary to spill extra water over the dam to avoid stressing it. A Corps official recently put the odds of serious flooding below the dam -- a heavily developed area of south King County -- at about 1 in 33. That's a significant improvement from the earlier odds of 1 in 3.
Still, people's eyes are on the skies this winter. So the climatologist's office has created this website to report precipitation recorded at two weather stations near the dam, as well as accumulated precipitation for the year. The data's put on graphs, alongside a 30-year precipitation average for those sites.
And here's some good news: The climatologist's office says that the forecast of an El Nino is fortunate for residents of the Green River Valley below the dam since, in Washington, El Nino cycles tend to "tip the odds towards drier average weather."