Prior Lake, Lower | Prior Lake Spring Lake Watershed District

Quick Facts

DNR Lake Number: 70002600
Surface Area: 940 acres
Average Depth: 13 feet
Maximum Depth: 56 feet
Ordinary High Water Level: 903.9 feet above sea level
Connectivity to other waterbodies: Water flows into Lower Prior from Upper Prior. The lake level is controlled by the outlet structure which feeds the Prior Lake Outlet Channel (PLOC).
Watershed Area: 18,904 acres
Public Boat Access: Located on the northern side of the lake from Sand Point (off of Crest Avenue).
Impairment Status: Impaired for mercury* and biota**
Bridge Clearance: The elevation at the bottom of Wagon Bridge (bridge under Highway 21) is approximately 911.5′. Subtract the current lake elevation from 911.5′ to get the approximate clearance.

*Mercury impairments are not handled at the local government level. The State of MN has a TMDL they are following here.

**Biota impairments are not handled at the local government level. The State of MN addresses impaired biota by examining the interactions of numerous physical, chemical, and biological processes that define community composition. Biological impairments can be driven by natural or unnatural changes to one or many components of these systems. Biological impairments differ from some traditional water quality impairments in that the impaired biotic communities are indicators of disturbance rather than causes of disturbance. Biological impairments are commonly caused by stressors that are not considered conventional pollutants. These include stressors such as degraded habitat or altered hydrology. Minnesota utilizes the process of stressor identification developed by the EPA to identify the dominant stressors.

Lake Levels

All lake level data below are approximate and preliminary – NOT to be used for legal purposes. Sudden drops or spikes are often due to calibration, which are manual adjustments to correct the lake level value. Please contact the PLSLWD office for official readings.

The outlet structure is open and operating as normal. The low-flow gate is not open at this time and is usually only open in springtime to allow additional storage for snow-melt and spring rains. Occasionally it is opened to help alleviate high-water during other seasons, but it is not designed for high water relief. The higher the lake gets, the less effective the low-flow gate is as the culvert nears max capacity.

For more information about the Outlet Structure, click here.

Occasionally, especially during cloudy weather, the level logger does not get service and the lake level does not get updated automatically on the graph below. This can sometimes go on for a couple days and there is nothing we can do. If you are in need of knowing the lake level, you can check the staff gauge on the NW pillar of Wagon Bridge (Hwy 21 bridge crossing Prior Lake, across the road from Knotty Oar Marina). Just add 900 to the number that you see to get the mean sea elevation.

The graph below displays the average of annual lake level readings, when available. Some years only had one lake level measurement so those would not reflect the “average” and could have been taken at any time of year. Also, some years are missing from this graph because no known data is available. The red line indicates when the weir was installed. Prior to the red line, there was no natural outlet for Prior Lake.

Flow

Estimated flow through the Prior Lake outlet structure based on past measurements of lake level and discharge. Note that the data is only valid for lake elevations between 902.5 and 903.75 and when the low-flow gate is closed. Use this table to estimate flow when low-flow gate is open. Stream discharge is calculated in cubic feet per second (cfs).

Water Temperature

Sensor is located in a well at the outlet structure roughly 2 feet into the lake sediment, so temperatures will not reflect surface conditions exactly.