Pond Boss Forums INTRO Questions & Observations Weekly Observations

Dwight do you see a groundwater effect and if so what aspect of the data is it effecting now ?

The ground water effect is seen in the water temperature on the bottom. You would expect that the most dense water at 39F degrees would be on the bottom. The ground water temperature remains at a relatively steady 41-42F degrees year around. As this warmer water flows through the pond it fights a losing battle with the colder pond water. At the bottom this warmer water isn't diluted as easily with colder pond water and therefore a layer of warm water remains at the bottom. There also may be some heating at the bottom from the hydraulic friction as the ground water circulates up and out of the pond sand and gravel bottom.

The bottom DO is affected by this warmer water as well. As we have noted warmer water holds less DO and ground water will have less DO then the pond water with it's oxygen producing plant life.

I think that there are other things going on with the "flow" such as stratification prevention, filtering, transferring of decaying material into the ground water table.

Thanks - a good analysis.

Updated Weekly
The heavy snow cover may already be affecting the D.O. The snow doesn't appear to have had much effect on the ice build which continues unabated.

You're right - the DO's sure are dropping. On the positive side, they are still VERY good.

Those DO lines need to level out and stop the drastic plunge. At least the temps have reached winter equilibrium. Could the ground water be effecting the DOs ?

Good point, Ewest. Years back, we had assumed that ground water would not have DO, and thus have been surprised over the years that the gravel/sand pits dug into the water table essentially never winterkill up here. So, your point is valid. We honestly don't understand what is happening with that groundwater percolation.

Updated Weekly
Ice is still building even with the snow cover. The ice consists of 17.5 inches of clear ice with an inch of cloudy ice on top.

Top and mid-range D.O. have turned corners and it appears the bottom D.O. is beginning to level out or at least isn't in free fall any longer.

My Sarge and I are both off for the MLK Holiday on Monday. We are heading to Bremer Pond to harass the fish. Since Dwight has been shoveling, it is one of the few places around here you can get on the ice without a snomobile or ATV. Bad news for the fish!

Starting to level near 9 ppm on the bottom looks great.

Interesting that the bottom temp is 41 F. Must be a groundwater effect. Good to see the DO stabilizing.

Ewest, we've sort of "struggled" with the bottom water temps ever since we started some winter monitoring several years ago, including Dwight's great work. Even in hill ponds, we're seeing 40-41 rather than 39. Ground water influence? Maybe some type of solar heating/radiation effect along the sides and bottoms? I assume that physics has not changed and 39 is still most dense. Another one of those "surprises" that we find when we translate from accepted knowledge to actually taking a look.

Speculation:

Geothermal heat release continually raises the temperature of bottom water, creating more >39 degree water than can quickly rise away in the absence of any none-density circulating forces under the ice. The density difference, and hence gravity-based mixing/moving force generated, between 39 and 41 degree water cannot be very large.

I assume Dwight's constant ground temperature is above 41 degrees. IIRC it's 52 degrees here in Central Ohio.

When I checked my well water temp coming from 66' below grade, it was 54*.

Theo -- we're about 46-48 ground water here, so I'll bet Dwight is similar to us.

I read somewhere that the annual average outdoor temperature of you area will be the same temperature as the ground water temperature. Ours is within two degrees at 46 degrees

Updated Weekly

The ice pack continues to thicken. Temperatures are pretty much stable. The bottom temp was actually 40.48 which rounds down to 40. The previous weeks it has been 40.50 plus which rounds up to 41. Hows that for minutia that matters?

The bottom D.O. continues down hill and if last winter is comparable to this winter the down trend will continue for several more weeks. The bottom D.O. reading is taken with the sensor probe sitting on the bottom. If the probe is raised 12 inches from the bottom the D.O. is at least a point higher. More Minutia that matters?

We just did some checking on a 7-acre and 3-acre pond here. We have far less DO than Dwight, but I'm not scared yet. Sure.... Everyone better hope for spring in a few weeks!

3-acre pond
Depth (ft)- D.O.- Temp C
4- 5.98- 2.2
8- 5.78- 2.5
11- 0.16- 5.0

7-acre pond
Depth (ft)- D.O.- Temp C
5- 8.43- 3.9-
10- 5.07- 4.3-
15- 1.42- 4.5-

Guess which one has the aerator (wind driven) going, and which has the broken aerator?

Dave, are those hill ponds?

My pond is staying a constant 5" of ice for now, but with the temps expected to be in the 40's for the next two days, and the the chance of 1" of rain, I don't think the ice will be safe for very long. I'll drag the thermometer out there tomorrow and see if I can get some water temps.

Dwight -- yes indeed, good man! You are absolutely right. These are some of the hill ponds that we manage. Our gravel/sand pits never have any DO problems, just like your pond.

Esshup -- we rained all day at 34 F, and the forecast tomorrow is up to an inch of rain at 35 F. Strange weather with 12 inches of darn snow on the ground. The rain has really started to drop the snow depths, so maybe we'll clear some ice on our ponds. They are forecasting some colder weather next week, with highs 18-20 and lows near 0. So we won't lose ice, but if we can even get the snow off the ice, that will help.

Interesting that the top and mid DO's are going up but the bottom is still falling. Wonder what effect the circulator is having.

Surprising the ice pack continues to thicken with all that snow on the top and moderate temps were are having. At midnight we are getting a steady medium rain. I wonder what that will do to the snow pack on the pond?