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Water Levels Update: March 17, 2020

Gray's Bay Dam Opened for 2020 Season

After close coordination and consultation with its partners and communities, Minnehaha Creek Watershed District (MCWD) opened the Gray's Bay Dam for the 2020 season on March 16.

The Gray’s Bay Dam is located at the outlet of Lake Minnetonka into Minnehaha Creek. The dam was built in 1979 to help control flooding on Minnehaha Creek and Lake Minnetonka. MCWD operates the dam according to a detailed operating plan developed over the course of 10 years with local, state, and federal partners.

See below for more details. 

March 18-19 Rain & Snow Event

The National Weather Service (NWS) is forecasting light rain on Wednesday which is anticipated to change over to snow on Thursday. Currently the precipitation totals for this event are foretasted to be less than a half-inch of rain and 1-inch of snow. MCWD does not anticipate this rain or snow to cause any flooding concerns at this time. 

Spring Flooding Outlook from NWS

On March 12, 2020, the NWS issued their final update for the spring 2020 snowmelt flood outlook. In that outlook the NWS identified that the risk for major/moderate flooding had decreased across the region, however, they noted that it could increase again if shift into a wetter pattern later in March or April. 

Lake Minnetonka & Gray's Bay Dam

As prescribed in the DNR approved dam operating plan, Lake Minnetonka was drawn down to 928.60 feet last fall to create storage for spring snowmelt, which allows the lake to be used as a storage basin. Lake Minnetonka's water level increased 7.4-inches over the winter. Last week the ice on Lake Minnetonka measured approximately 16-18 inches thick. Currently MCWD estimates the Lake Minnetonka level is approximately 929.22 feet above sea level. 

Lake Minnetonka water level graph

After tracking ice conditions with Minnehaha Creek communities, the condition are now suitable for dam discharge into the creek. The Gray's Bay Dam was opened for the 2020 season on Monday, March 16 and is currently discharging 50 cubic feet per second. 

While MCWD staff are working remotely until at least March 30, 2020, in order to prevent the spread of COVID-19, staff will continue to operate the dam normally. 


 

Minnehaha Creek

  • Minnehaha Creek is currently flowing around 36 cubic feet per (cfs) second at Hiawatha Avenue
  • Ice jam concerns have subsided
  • We expect creek flows to stay under 100 cfs during the rain and snow event later this week

Minnehaha Creek level graph

Lake Nokomis (Minneapolis)

  • Yesterday the Lake Nokomis water level reading was approximately 815.29 feet above sea level, which is 1.3 inches below the ordinary high water level of 815.40 feet
  • The Lake Nokomis weir was left open all winter to allow the lake to discharge into Minnehaha Creek and continues to remain open
  • Minneapolis Park & Recreation Board and MCWD staff will continue to coordinate on the operation the Lake Nokomis weir

Lake Nokomis weir discharging into creek

Lake Harriet (Minneapolis)

  • Yesterday's Lake Harriet lake level reading was 847.75 feet above sea level, which is 3 inches below the ordinary high level of 848 feet

Spring 2020 Flood Risk Coordination 

On February 25, 2020, MCWD in coordination with the National Weather Service (NWS), the U.S. Geological Survey, Hennepin County Emergency Management, and Carver County Emergency Management, hosted a flood risk briefing for city and agency staff across our watershed district.  

Through this briefing, staff from these agencies:

  • Outlined the current flooding risk outlook for spring 2020
  • Shared information about managing the potential impacts of flooding
  • Highlighted the services that MCWD and other agencies could provide
  • Identified ways to share flooding data

Attendees at the flood briefing

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