August 18 Rainfall Summary & Water Levels Update
Rainfall totals on August 18 were higher than anticipated and according to the Hennepin County Mesonet weather stations, totaled on average between approximately 1.6 – 2.1 inches across the watershed (see map below). This brings the Twin Cities’ total precipitation this year to 29.64, which is 9.14 inches above normal.
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Second Wettest Year to Date
The rain this past weekend pushed the Twin Cities to the second wettest year to date (since record keeping began in 1871) with 29.64 inches of rain falling between Jan. 1 – Aug. 18. For comparison, in a normal year the Twin Cities receives approximately 30.61 inches of precipitation total (from Jan. 1 - Dec. 31).
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July 2019 Hydrologic Conditions Report
Last week the MN Department of Natural Resources (DNR) released the July 2019 Hydrologic Conditions Report. It identified that:
- Most lakes saw decreasing elevations over the month, however, 71% of gauged lakes showed July lake elevations above their average lake level
- Over 68% of these “above average” lakes reported lake elevations more than half a foot higher than their average
- Groundwater levels in July remained relatively high and were above normal water levels in southern Minnesota
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Lake Minnetonka & Gray's Bay Dam
- The August 18 rain event caused Lake Minnetonka’s water level to increase 1.56 inches to an elevation of 929.38 feet above sea level (see graph below), which is 0.24 inches below the ordinary high water level of 929.40
- It is likely that Lake Minnetonka’s water level will remain at approximately 929.38 feet for the next few days as upper watershed streams continue to drain into the lake
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- At the beginning of August dam discharge was reduced to 75 cubic feet per second (cfs) due to conditions allowing the Gray's Bay Dam to be operated in “Zone 4” of the operating plan (see graph below)
- The dam discharge was reduced again on August 12 to 50 cfs and has remained at 50 cfs since then
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Minnehaha Creek
- Despite the dam discharge being lowered to 50 - 75 cfs for over the past two weeks, Minnehaha Creek flows have still remained above approximately 130 cfs. This is because the wetlands and floodplains along the creek continue to drain water into the creek
- Before the rain on Sunday morning, the creek was flowing around 130 cfs
- Minnehaha Creek flow nearly quadrupled during the rain due to stormwater runoff and peaked at 507 cfs at 4:00am on August 18
- Minnehaha Creek’s flow is steadily dropping and is currently flowing around 200 cfs
- MCWD is advising people that it is unsafe to paddle the creek at this time. Ideal creek flow for paddling is between 75 - 150 cfs. Flows above 150 cfs can make it difficult to react to obstacles (downed trees, branches, etc) in the creek and to pass under some bridges. There are some obstacles in the creek, as city crews are working to remove them as they are able. Learn more about paddling conditions
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Lake Nokomis (Minneapolis)
- The August 18 rain event caused Lake Nokomis’ lake level to increase 6.84 inches to an elevation of 816.23 feet above sea level, which is 9.96 inches above the ordinary high water (OHW) level of 815.40
- Despite the record setting rain, operation of the Nokomis weir allowed the lake to fall below the OHW (815.40 feet) early last week
- The Minneapolis Park and Recreation Board (MPRB) closed the weir ahead of the last two rain events to prevent Minnehaha Creek from flowing into the lake
- Once creek levels subside this week and the chance for rain is gone, MPRB plans to reopen the weir on Tuesday or Wednesday
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Lake Hiawatha (Minneapolis)
- Yesterday's Lake Hiawatha level reading was 814.39 feet above sea level, which is approximately 1.59 feet above the ordinary high water level of 812.8 feet
- The current lake level is approximately 1.31 feet below the berm that separates Lake Hiawatha from the Hiawatha Golf Course
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Mooney Lake (Plymouth)
- Yesterday’s Mooney Lake reading was 989.85 feet above sea level, which is approximately 1.85 feet above the ordinary high water level of 988 feet
- The Mooney Lake emergency pump is turned on whenever the lake level reaches the elevation of 990 feet between March – September and will remain on until the lake falls below 989 feet
- MCWD in coordination with the City of Plymouth and the City of Wayzata collectively determined that all the necessary parameters had been met and the emergency pumps were turned on April 19 and continue to operate
- During the pumping, MCWD will monitor downstream water bodies to see if any high water conditions exist
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Record Setting Precipitation
The spring of 2019 was exceptionally wet which continued a record setting wet trend that started in 2013. The MN Department of Natural Resources (DNR) State Climatology office has observed that 2013 - 2018 finished as the wettest six-year period on record since record keeping began in the 1870s. During those six years an extra year’s worth of precipitation fell (~30 inches), meaning we have received seven years’ worth of rain in a six-year period. 2019 continued this wet trend not only across Minnesota, but across the entire contiguous United States.
The 2019 spring flooding resulted in over $32 million in estimated damages to public property and infrastructure across 50 counties and four tribal nations across the State of Minnesota.
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Looking Ahead & Coordination with Agency Experts
The seven day forecast from the National Weather Service shows relatively dry weather and the two-week outlook calls for average precipitation.
Since March, MCWD has been actively coordinating with staff from the National Weather Service, U.S. Geological Survey, and Hennepin County Emergency Management to understand spring flooding predictions, water content of snow, current stream flows, and emergency coordination efforts. Prior to snowmelt, MCWD ran several hydrologic snowmelt modeling scenarios to identify the locations that could face potential spring flood risk. We coordinated the results of this modeling, as well as modeling for the upcoming rain event, with all 29 communities in the MCWD.
MCWD will continue to coordinate daily with agency partners, National Weather Service, U.S. Geological Survey, and Hennepin County Emergency Management to consult and review data to help inform Gray's Bay Dam operations.
The National Weather Service provides MCWD with seven-day precipitation forecasts and a prediction for how that precipitation will affect water levels. With this information, we can proactively create storage for the forecasted precipitation. Dam discharge can then be reduced before rainstorms and that storage is used to prevent flooding on Minnehaha Creek. MCWD also uses real-time weather data provided by Hennepin West Mesonet weather stations installed on MCWD properties and real-time water level data from the U.S. Geological Survey gauges on Lake Minnetonka and Minnehaha Creek.
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Tips for Property Owners
Get the latest information by visiting our website and signing up for email updates.
Review your insurance coverage. There is a 30-day waiting period before a flood insurance policy takes effect. Learn more about flood insurance. Check to see if your policy covers sanitary sewer back-ups. More information is available from the Insurance Information Institute.
For specific questions about local flood response, including where to find sand bags and other resources, contact your city.
Minnehaha Creek
- Edina – Dave Goergen, Public Works Coordinator, 952-292-6225
- Hopkins - Hopkins Public Works, 952-939-1382
- Minneapolis - 311 or 612-673-3000
- Minnetonka – Minnetonka Public Works, 952-988-8400 between 7am-3:30pm
- St. Louis Park – Steve Koering, Fire Chief, 612-790-4019
Lake Minnetonka
- Deephaven – Dana Young, City Administrator, 952-358-9939
- Excelsior - Tim Amundsen, Public Works Superintendent, 952-653-3676
- Greenwood - Dana Young, City Clerk, 952-358-9939
- Orono – 952-249-4600, after hours call Dispatch at 952-258-5321
- Wayzata – Mike Kelly, City Engineer/Director of Public Works, 952-404-5316
If your home is impacted by flooding, please report it to Hennepin County Emergency Management at 612-596-0245.
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