Devils Lake Likely Near 2010 Summer Peak

As the overall wet cycle continues to impact the region, Devils Lake also continues to respond. Unfortunately, there have been several significant rain events this summer which, when combined with the spring snow melt, has caused the Lake to continue its rise. Since the end of March 2010, Devils Lake has risen from 1450.47* to 1452.25* feet. [*These values are provisional, based on data collected by the USGS at the Creel Bay gauging station.] What about the rest of the summer and fall, 2010? Has Devils Lake peaked for this year? The obvious answer lies in future precipitation, how much falls, over what time period and how much of the Basin is impacted. Little or no rain would result in a gradual fall through winter freeze up; much above normal rain would cause the Lake to resume its rise.

Historically, precipitation amounts across the Devils Lake Basin have peaked, and a gradual decrease in rainfall is common during August and September. However, with the ongoing wet cycle expected to continue, there is still the potential for above normal rainfall amounts into this fall. The near term (8 to 14 day) and longer term (3 month) climate outlooks suggest above normal rainfall will continue over the region. How much rainfall, especially in the longer term, cannot be predicted. We therefore rely on the historical record and the Lake's response to estimate future Lake levels.

Looking at observed lake level variations [1949 to 2007], there is a high level of confidence the Lake should fluctuate about 0.1 foot through September due to normal climatic variability. This indicates that evaporation and precipitation would be nearly balanced for the remainder of the summer and into the early fall season.

Technical description: Using standard statistical methods on the Devils Lake volumes for the years from 1949 to 2007, the mean of 5-day standard deviations (Lake-wide fluctuation) covering the outlook period of July 19th through October 25th 2010 was calculated to be 2038 acre-feet. Twice this would give the 95% confidence level for a normal distribution. Devils Lake at this time (July 28th 2010) is at 1451.9 feet with a volume of 3,129,029 acre-feet (taken from USGS data). Applying twice the average standard deviation for the outlook’s valid period, there would be a 95% confidence that Devils Lake would stay close to 1452 feet (3,133,105 acre-feet).

The graphic below represents the July 20 2010 run of the AHPS model, which predicts the Lake level though the end of October 2010. The lower probabilities are associated with the wetter late summer and early fall years, while the higher probabilities are associated with the drier years.

AHPS run output



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