Who “controls” Lake Edward water levels?      

The answer is no one, except an occasional beaver building temporary dams.  The outlet weir to Ditch 13 is concrete and can not be adjusted. The outlet elevation of 1206.7 is legally fixed federally by the U.S. Army Corps of Engineers and more locally by the State of MN.  There are no human-adjustable controls on the outflow from Lake Edward.    

 

So what changes the lake level? 

The lake level is a natural balancing act between water entering the lake minus water leaving the lake.  The category of water entering the lake includes surface runoff of precipitation in our 8,000- acre watershed plus groundwater moving into the lake from precipitation that has percolated down into the groundwater.   Water leaving the lake includes Ditch 13 (when lake levels are high enough for flows in Ditch 13), evaporation and plant photosynthesis (can add up to several feet of water over the year) plus groundwater flows out.  In our case, groundwater moves generally from Pelican Lake toward Edward to North Long Lake and then further down to Gull Lake and the Mississippi River.  In the bigger picture, Ditch 13 is normally not a substantial factor in the balancing act that determines the level of Lake Edward.  Ditch 13 only becomes a substantial flow factor when Lake Edward is higher, say around its record high level which was 1208.18 in 2001.  And even at those elevations, flows through the outlet culvert approach only 25 cubic feet per second (cfs), an impressive sight, but a small flow compared to the volume of water in the top two feet of the lake when its historically high.

 

Does the lake water level drop througout the summer even when we get rain?    

The lake level is a balancing act of a number of factors.  One factor is precipitation - how much it rains.  Another is humidity - dry days cause higher levels of evaporation. On dry windy days, researchers have found that several inches of water can evaporate from lake surfaces each day and and a bit more water loss by evapotranspiration through plant leaves as plants photosynthesis their food. The level of the wetlands can also be a signal - if they are less full than before it indicates some drop in ground water.  So the resulting balancing act will result in the lake water level dropping to near its long-term average water level. 

 

What is Ditch 13? 

There is a small man-made outlet from Lake Edward in the south end that becomes Crow Wing County Ditch 13. Ditch 13 flows into a wetland that can be seen from the rparking lot at the NE corner of the round-a-bout intersection of CR 3 and CR 4. Then Ditch 13 flows into a wide concrete culvert under CR 4 just north of the round-a-bout. 

 

This is a map of the route of Crow Wing County Ditch 13 which is maintained by the Crow Wing County Highway Maintenance Department.  The culvert location is marked on the map with a bright pink box:

How did we get a concrete outlet culvert to Ditch 13? 

We are fortunate that by about 2006, the historic smaller steel outlet culvert was replaced with the fantastic new oval-shaped concrete culvert that we now see. The current concrete culvert has far more flow capacity than the previous old steel culvert that it replaced. But the culvert is sort of “perched” at a higher elevation to help us when Lake Edward gets historically high.  Average Lake Edward water levels are low enough that hardly any or no water leaves the lake over the weir.  For comparison, the elevation of the low part of the weir is 1206.7 and the historic average lake level is even lower, about 1206.5. So that means at the current average lake level, Lake Edward is about 0.2 (2-1.2 inches) below the lake elevation that would be necessary to flow out over the fixed concrete weir.

  

The following older picture shows that there is no adjustable control at the concrete culvert under CR 4 where Ditch 13 exits the Lake Edward vicinity.  This is just a solid concrete weir that water in Ditch 13 must pass over to continue down Ditch 13 to North Long Lake. (Note that the County Highway Maintenance folks have had the cattails cleared from the intake side after this older photo was taken. Water can flow freely when high enough to go over the weir.)