Lake Water Quality

[Such_a_brett]

Does anyone have specific info on what would be considered the most optimal water turnover in a man-made ski lake. At our new project, we have the ability to control the flow of water through the lakes. Some flow keeps the water fresh and slows the pressure from algae and other growth. Too fast would keep the water unnecessarily colder and also eliminate the ability to use dyes.

 

For additional detail, one lake is 10 acres surface area and 7 feet deep. The other is 25 acres and 15 feet deep. The source water is about 55-60 degrees. Northern UT, so the summer is very hot and dry.

[lpskier]

Won’t you lose a lot of water to evaporation? Not that evaporation is bad, but you’ll need to factor evaporation loss into your turnover equation.

 

If your turnover rate controls your algae, why do you need dye? Weeds/grass? If so, try some carp to control weed and grass growth.

 

Our water is in the 80’s already here in Florida. I’d take some of that 55-60 degree water right about now. And all summer!

[Horton]

if I had a choice I would let my lake be cold, dye and algae free.

[kmenard]

@Horton you can move your lake to Canada :)

[igkya]

@horton your definition of 'cold' is most likely very different from most.

[lpskier]

I’d say my favorite water temp is 68-75 F.

[skihacker]

@lpskier that's probably where my ski works the best but if I'm being honest my body is a lot happier at 85 or so. Right now it's 55 which sucks for everything but beats the heck out of shoveling snow!!

[Zman]

For one of your lakes, at 7 feet depth, my experience is that you are right at the depth where weeds may or may not take hold. In GA, I was on a lake where the weeds mostly only existed where depths were 6 feet or less. That can vary depending on location (temps) and variety of weed.

The deeper lake may only be an issue along shorelines. Again, not hard and fast guide, there are plenty of variable.

Go with more flow, cooler temps.

May want to add a small amount of grass carp to eat any growth as it gets started, if you start to see any concern. A little grassy growth along the shores should be fine.

 

[Horton]

You guys are reminding me that I need to go put in some dye today. I really hate the stuff but with a rock shoreline we do not have any clay in suspension ( aka erosion ) so if I do not hammer the dye that lake will be all weeds by July. Dye is better than herbicides but I is not pretty.

[lpskier]

@Horton Have you tried fish? Or no bueno in CA?

[kmenard]

@Horton Then you aren't doing it right...

 

 

[Such_a_brett]

@lpskier

 

The evaporation is accounted for. In this region we have approximately 2 acre-feet of evaporation each year from Apr-Oct. But that is very small compared to the water exchange rate we can build into the lakes. For example, if we wanted the water to exchange completely once a month, we'd design for about 6.5 cubic feet per second inflow. making up for evaporation would only add another 0.33cfs to that. I guess that isn't really a small amount of water, as it is still about 150 gallons per minute. But within the larger picture of building a recharge lake, the groundwater seepage is many times greater than the evaporation.

 

@Horton

 

I think "cold" is probably a relative term. If we pull from the river, it is straight snow melt until early July, so injecting 40F water into the lake is less than desirable. Once we get into July it is primarily spring water, so closer to 50F, but that is still very cold to spend time in. Ideally it would be closer to 70-75F most of the season.

[Such_a_brett]

@Zman

 

Thanks for the tips. We don't really have to worry about shoreline growth as much. From 24" below water to 18" above water the shoreline consists of 8oz non-woven black geofabric with 6" of beach sand over it, except in the turn areas where it is river pebble over the geofabric. That won't eliminate growth, but will surely slow it.

 

The community has a 5-man full time landscape/lake maintenance crew to take care of any undesirable growth. A tractor with a drag mat should work nicely for both weed growth and erosion control. Also, home owners are required to maintain their section above the waterline.