DNR News Release 7/27/22

Declining water levels in parts of state affecting boat launches and retrievals

Low water levels, resulting from below-average rainfall in much of the southern third of Minnesota in June and July, are making boat launching and retrieval challenging at many lakes and rivers, especially in the Twin Cities metro area. 

When water levels decline, less of the boat ramp is underwater, which reduces the length of the ramp available for a successful launch. As a result, there is a greater chance of backing a trailer past the end of the ramp when launching. Ramps can be extended in some places to reduce this risk, but this is not effective where shallow water persists well beyond the boat ramp.

Another low-water hazard to consider is the possibility of a prop-wash hole at the end of a boat ramp.  Prop-wash holes are caused by power loading, which happens when boat operators use the motor to load the watercraft onto the trailer instead of cranking the boat onto the trailer with the winch.  The motor scours a hole in the sand and gravel at the end of the boat ramp. Subsequent, unsuspecting boaters can back into the prop-wash hole with their trailer.

“It’s difficult to get a trailer unstuck from a prop-wash hole,” said Nancy Stewart, DNR water recreation consultant. "Also, in the area past the hole, there is often a mound of sand or rock deposited by power loading. Boats can run aground on this material and not be able to get to deep water.”

To successfully launch boats in low water conditions:

• Check the ramp, especially the firmness of the gravel at the end of the concrete ramp and the water depth.
• Use smaller watercraft or a different waterbody if the ramp you normally use is too shallow.
• Expect delays at public access sites and be patient with boaters who are having difficulty launching.
• Watch for obstructions in the water near the access, like large boulders or tree stumps.

To prevent damage to boat ramps, trailers and boats, boat operators should avoid power loading at all times -- not just when water levels are low. For more information and to see an illustration of power loading impacts, visit the DNR website (mndnr.gov/Water_Access/Powerloading.html).

Brian Vlach of Three Rivers Parks concurred, their testing of the lake waters found no dissolved oxygen below 4-m, which is typical for the lake almost every year.  This limits the fish to seeking refuge in upper stratified layer (epilimnion) where water temperatures have been suboptimal on the high side of 85° F.  If fish are subjected to these conditions over a long period of time, then they can get stressed out making them more vulnerable to diseases such as bacteria and viruses.  In a way, this is very similar to people where their immune system becomes compromised and vulnerable to getting sick when we are stressed out for long periods of time.   

The difference this year could be the presence of a specific bacteria spp. and the number of fish for that year class and species that were vulnerable (in this case crappie).  The stressful conditions + bacteria + a strong year class that is susceptible to the bacteria = fish kill.  It is difficult to attribute this fish kill to one thing specifically, but more of a combination of factors that happened to occur at the same time period. 

Hopefully this event has run it's course. If more information becomes available it will be posted here.

.