Potential for Localized Flooding September 11-13

The National Weather Service (NWS) is forecasting 3-4 inches of rain across the Minnehaha Creek watershed starting Monday evening and continuing into Friday. Approximately 1-inch of rain is expected today (Sept. 9), however, multiple rounds of showers and thunderstorms are expected to bring heavy rainfall amounts of 2-3 inches starting Wednesday (Sept. 11) through the early morning of Friday (Sept. 13).

Keep in mind the month of September usually observes around 3-inches of rain, therefore, it's possible we may receive a typical September's worth of rain in the next five days. With 2019 already being a record wet year and causing water levels to be elevated, MCWD is advising communities across MCWD about the likelihood of localized flooding. 

Lake Minnetonka & Gray's Bay Dam

• MCWD has been tracking the NWS long-range forecast which was predicting above average precipitation for mid-September. Due to this prediction MCWD has been proactively creating space in Lake Minnetonka for this predicted wet weather. 
• The current Lake Minnetonka elevation is 929.16 feet above sea level
  • The "ideal" lake elevation for this time of year is approximately 929.10 feet

• To create storage capacity in Minnehaha Creek for this predicted rain, the Gray's Bay Dam discharge was reduced this morning to 50 cubic feet per second (cfs)
• We estimate that this rain will increase Lake Minnetonka's level to approximately 929.50 - 929.60 feet which could cause the dam operations to move to "Zone 3" which is noted as the red line in the dam operating plan graph below
  • Assuming Lake Minnetonka rises to at least 929.50 feet, and there is capacity in Minnehaha Creek, we will likely increase the dam discharge this upcoming weekend or early next week to regain storage capacity and as we work to draw down the lake to the desired elevation of 928.60 feet every fall season

Minnehaha Creek

• Minnehaha Creek is currently flowing ~187 cubic feet per second according to the United State Geological Survey (USGS) at Hiawatha Avenue
• We estimate that the rain between Wednesday (9/11) and Friday (9/13) could cause Minnehaha Creek to jump to over 400 cfs which would push the creek out of its banks in some locations
• 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

Lake Hiawatha (Minneapolis)

• Today's Lake Hiawatha water level reading is 813.9 feet above sea level, which is approximately 1.1 feet above the ordinary high water level of 812.8 feet
• The current lake level is approximately 1.8 feet below the berm that separates Lake Hiawatha from the Hiawatha Golf Course

Lake Nokomis (Minneapolis)

• Today's Lake Nokomis’ water level reading is 815.48 feet above sea level, which is less than one-inch above the ordinary high level of 815.40 feet
• Despite the record setting rain in 2019, recent operation of the weir has lowered the lake over 1-foot over the past 19 days
• The Minneapolis Park and Recreation Board (MPRB) closed the weir yesterday (Sept. 8) ahead of the the predicted rain today to prevent Minnehaha Creek from flowing into the lake
• MPRB and MCWD staff will continue to look for opportunities to open the weir to allow the lake to drain into Minnehaha Creek while still protecting the lake from inflows from the creek

Lake Harriet (Minneapolis)

• Today's Lake Harriet water level reading is 848.54 feet above sea level, which is approximately 6.48 inches above the ordinary high water level of 848 feet

Mooney Lake (Plymouth)

• Yesterday’s Mooney Lake reading was 989.25 feet above sea level, which is approximately 1.25 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  

Mary Lake (Shorewood)

• Mary Lake's current elevation is approximately 955.5 feet above sea level, which is approximately 3.5 feet above its estimated ordinary high water level of 952 feet
• The City of Shorewood was issued a DNR Water Appropriations permit to temporary pump up to 4.5 million gallons of surface water from Mary Lake to lower the lake level to prevent flooding of homes
• The pumping of Mary Lake will stop when the water level of Lake Mary reaches 952 feet 
• The discharged water from Mary Lake is being pumped to Lake Linden which is being monitored for high water as well

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 Twin Cities had the 2^nd wettest January 1 – August 18 on record
• The Twin Cities had the 8^th wettest spring on record (March 1 – May 28)
• The Twin Cities had the 11^th wettest May on record
  • Total May 2019 precipitation was 6.68 inches, which is 3.76 inches above average for the month
• The State of Minnesota had the 4^th wettest 12-month period on record (May 2018 - April 2019)
• The United States experienced the wettest 12-month period on record (May 2018 - April 2019)
• For the third consecutive time in 2019 (April, May, June) the United States experienced the wettest 12-month period on record (July 2018 – June 2018)

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.

Looking Ahead & Coordination with Agency Experts

The two-week outlook from the National Weather Service shows above 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.

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

• 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

Water Level Resources

• Track updates on Twitter by following @graysbaydam
• Current and historical lake levels and discharge rates can be viewed on our website
  • We recently added an "Explanation" column to provide insight into why the dam adjustment was made
• USGS automated lake level reading of Lake Minnetonka
• USGS automated flow and height reading of Minnehaha Creek at Hiawatha Ave