As you know, Scott County had been under a flood watch. Prior Lake-Spring Lake Watershed District staff are consistently keeping an eye on this and other rain forecasts predicted by NOAA so that we may effectively manage the low-flow gate of the Prior Lake Outlet Channel.
There are many factors that must be taken into account prior to opening the low-flow gate including, but not limited to:
- Short-term and long-term predicted precipitation amounts
- Current lake levels on both Spring Lake and Prior Lake
- Recent history of precipitation in the watershed (saturation levels)
- Potential risk to cause detrimental conditions (e.g. undesirable low lake levels)
- Amount of water storage available in the Upper Watershed
In addition, District staff also need to seek permission from the DNR to open the low-flow gate. Last month, the low-flow gate was opened for an approximate duration of one month. The DNR only gave permission to the District to lower the lake level to 902.5 feet above mean sea level (MSL) at which point the gate was closed.
Prior Lake water levels for reference:
902.5 MSL – normal water level
903.9 MSL – ordinary high water level
904.0 MSL – No wake level, Watersedge Trail starts to see flooding
905.5 MSL – Other road segments begin to flood
Both Prior Lake and Spring Lake rose 0.12 feet as a result of last night’s rain events and are staying relatively steady at that level at 902.68 MSL. The District’s current monitoring information indicate that the upper watershed is not contributing a lot of runoff and the upper watershed storage is not full. Spring Lake and Prior Lake are letting out water at approximately the same amount, which means Spring Lake watershed is not causing Prior Lake levels to rise.
According to NOAA, the flash flood warning has now been called-off and the chance of rain has decreased significantly. Based on watershed storage conditions and the current forecast, the PLSLWD and City of Prior Lake do not see an immediate need to open the low-flow gate at this time. However, staff will continue to watch the weather forecast closely.