Pond Boss Forums AERATION Systems questions Ground water circulation to cool / aerate?

Hello everyone! First off, thank you everyone for all the informatin that I've obtained from hiding I've been visiting this sight for several years and I finally have a question to post (and hopefully some potential ideas for others).

Background:
I had a pond dug on my property in Northwestern Michigan in the summer of 2010. The site is at the bottom of a very steep ridge and the ground water level is anywhere from 2-4 feet below ground level depending on rainfall, temps, etc. The property is 100% pure sand. While the pond was being dug (via old giant military drag link crane) the hole filled almost as fast as it was dug. The deepest part (as of 2 weeks ago when I measured) was approx 8 feet deep. It has steep sides and is approx 1/4 acres. The only fish in the pond right now is 1 male bluegill transferred from my home pond (of 6 acres) and 12 goldfish that my knucklehead buddy threw in without my knowledge. These were a test for overwintering. They have all lived (and grown HUGE) over 2 winters. Last winter I went up with the family in hopes of ice skating and there was 12" of open water around the edge even though the temps were below 0 deg F for the previous week (does this mean a possible spring or extremely strong groundwater flow?).

The Goal:
So I want to keep trout in the pond (like everyone else!). I'm assuming that I don't have a strong groundwater flow and I don't have any acutal springs. I know I need to keep the temps below 68ish (I will take a temperature measurement from both bottom and top of the water column this weekend which should represent a fair assessment of the warmest the water I should ever see based on this rediculously hot summer so far). I did measure the temp last year the first week in August (also the lowest water level) and it was 73 on top and significantly colder on the bottom (didn't measure down deep).

The Question:
If the water temp is too warm and /or the DO is too low, has anyone ever tried pumping water from their pond out and allowing the groundwater to refill? The water seeping in is significantly colder even at the top when felt along the shoreline. My thoughts are since I'm on 100% sand, the water pumped out will disapate and the fresh, cold, oxygenated groundwater will refill it and I will have solved my circulation / temperature issues. I realize not all ground water is created equal and it may need to be aerated, but the temperature thing is the hardest for me to solve.

I am considering getting my buddy back out with his big old machine (which is capable of digging to 25 feet!) and having him go down another 5 feet or so....

Any input would help out a ton!!

Thanks!!

just some thoughts from a noob-

if you are not aerating/circulating the water, you should get a layer of really warm water to sit on the surface.

i periodically let this warm surface layer build up (by turning off the aeration for a few days), and then push off this warm water through my surface spillway by letting in fresh cold water. in my case this water comes from a cold creek, for you maybe enough groundwater is infiltrating to get the same effect.

once the warm water layer has left the pond, i restart the aeration.
this cycle takes about a week for me, and helps to keep the water cold and oxygenated.

the deeper your pond the better this temperature stratification will occur. so yes, all things equal, more depth gives you a better opportunity to 'work' the thermocline to push off the warmest water. fwiw, my pond is 15 feet deep.

good luck-
adam

good luck,
adam

Up North John:

I learned a valuable lesson with ponds dug in sand. If the sides of the pond aren't sloped 4:1 or less, the sand on the sides of the pond will slowly slide to the bottom. It will do that fast or slow, depending on the degree of slope. A friend has a pond that was dug in sand, with a trench down the center of the pond. It was dug with an excavator. The trench was about 3' deep (bucket depth) but I don't know how wide it was. The pond was completed in August, and in December I measured the pond depth by cutting holes in the ice. That trench already had collapsed and flattened out, so the trench now was only 6" deep but about 10' wide.

Not all groundwater has O2 in it. Yes, I think you are on the right track thinking that the ground water flow kept your pond ice open during the winter. My pond is a groundwater pond, and if there is normal rainfall during the year the water in the pond will be 4 to 5 degrees warmer than the local lake that is 2 miles away, and the ice will be less than half the thickness of the ice on the lake.

I've noticed this in my pond as well. It appears to only be about 6" deep from the top down excpet the temp ~12" out from the pond walls gets significantly cooler. I'm assuming this is from cold ground water seepage.

ESSHUP:

I've already noticed this as well. The deepest part of my pond was originally 10 foot deep and that ended up around 8' by the end of the first year. The sand 'creep' has appeared to slow down at this point, but it's still a big concern for me. My only saving grace at this point is the large amount of vegitation along the banks that I hope is stablizing the side walls.....