Pond Boss Forums POND CONSTRUCTION Selecting a site Pond Depth

I am looking for opinions on pond depth. I am in northern lower Michigan, 1/4 acre water table pond (basically the water flows through the sand that sits on top of thick laver of clay.) I have seen a wide range of recommend pond depths, which I suppose depends on the specifics of each pond. Most recommendations are for 12-15ft deep, which for a 1/4 acre oval shaped pond is proving to be somewhat of a challenge. What is the purpose of this depth? Is it as a heat sink? Is it for dissolved oxygen storage, (I thought the deep water is unusable because of the low do anyway?) Would a larger area of 10Ft deep provide better, worse, equal to a smaller area of 12-15ft.?

One reason for pond depth when thinking of 'northern' waters is how thick the ice may get during the winter.

Generally, there will be a thermocline where the water below is not used much by fish, and the water above is used by the fish.

Do you have AC electricity available at the pond?

Inexpensive aeration will let you trade off some of the normal reasons for additional depth.

Yes planning on year round aeration, deep in summer, shallow in winter.

Great, that will be a huge benefit to your fish management.

I am definitely NOT an expert, but I think the pond depth reasoning goes something like this:

1.) Extra water depth (beyond the typical "usable" depth) is most important for ponds with significant water fluctuations. We have some Texas guys whose ponds are currently down 5'. This would result in some huge stress on the fish if the normal pond depth was only 7'

2.) Control of aquatic plants. Rooted aquatic plants are obviously dependent on sunlight for establishment and growth. Other photosynthesizing organisms (like filamentous algae) can also establish themselves on the bottom, even though they are not truly rooted. Most ponds have habitat for plenty of plants in the space from the waterline down the slope into deeper water where sunlight finally becomes insufficient. The slope is generally designed to get the pond OUT of the good plant zone as soon as reasonably possible.

A pond will typically be more productive for fish when it has a significant amount of water that is deeper than the "optimal" plant growth zone. Usually your state agency will have some "rules of thumb" for the correct depth for ponds in the state. Obviously, there are some important variables on plant growth (like water clarity), but the guidelines are a good starting place.

3.) Deeper water MAY provide some additional oxygen supply to the pond. You are correct that deeper water in a small pond typically stratifies in the summer and is just an area of water with very low dissolved oxygen that is NOT utilized by the fish.

However, cooler water can hold more dissolved oxygen at saturation. There are several people on the forum that have creatively used their aeration and the cooler, deep water in their ponds to carry their fish through some significant weather stress. (You might search for some of those threads when you are planning your aeration system.)

4.) Deeper water may be required as a WINTER refuge. A shallow pond at your latitude could definitely freeze all of the way to the bottom during a cold winter. However, I believe if your pond is deep enough for the requirements listed previously, then you will not have that problem.

HOWEVER, a shallower pond will ice over earlier. A snow covered pond in your area has the potential for the cessation of photosynthesis in the water under the ice. That most definitely can result in a fish kill. There are also good threads on the forum from the people with northern ponds using shallow aeration to avoid winter fish kills.

5.) Deeper water gives you accommodation for bottom infilling of your pond! I think this is more important than 3.) or 4.). There are stories of people with properly constructed and sloped ponds that were subjected to a frog-strangler rain prior to grass being re-established around the pond. They lost 1-2' of depth overnight as silt was washed into the bottom of their pond. Silt from plowed fields in your watershed, or muck buildup due to the accumulation of leaves and twigs will also slowly steal your pond depth.

In summary, I think if you could get some 10' deep water in your 1/4-acre pond, that would be sufficient. Also, sometimes you just have to take what the ground gives you (unless you want to beat it down with money). If you find a gravel patch that goes to 13', then dig out the entire thing. Compact a 1' blanket of clay above your deepest scoop (in 6" lifts) and then you will have a small portion of the pond that is 12' deep.

Hopefully, some of the members from your region will correct any boneheaded points in my reply.

Good luck on your new pond!

Question about ground water ponds. Is the water in the pond moving like an under water river, or once it fills it just stays in the pond? If it is moving then it is being replaced with water with no oxygen. Aeration makes this a null subject, but just quercous.

Sounds like your question is choosing between, a 12-15ft 1/4acre, and a 10ft (maybe 1/3 acre)?
I'd go with the larger one, 10ft is plenty of depth.

With a groundwater based pond, all the "traditional" pond depth thoughts need to be tossed out the window. (In my opinion). My take on groundwater ponds is make the pond as deep as the type of soil allows (slope wise). Here is my reasoning behind it (and the reasoning is because my personal pond is a ground water pond)

You have no control over the amount of water in your pond with a groundwater pond. You are completely at the mercy of the elements. Say you were to start out with a pond that has a maximum depth of 10 feet. What happens when the ground water level drops? Yep, the pond level drops.

Not a big deal you may think. Well, think again. My pond was full, going out the overflow in April 2020. The rain faucet shut off in June 2020. By November 2020 my pond was down 7 vertical feet. If I had only dug my pond to 10' depth when I renovated it, I'd only have 3' of water in the deepest part. As it is, the water level stayed that low for around 16 months and now it is still 4' low. My 1 1/8 to 1 1/4 acre pond went down to a hair under 1/2 acre. I had to take out a LOT of fish and really watch the O2 and Ammonia/nitrate levels to ensure I didn't have a fish kill due to more biomass in the available water volume.

In my pond the water movement is obvious when digging stirring up mud. The areas where the water enters quickly becomes clear and the outlet will be muddy all the way to the edge. I have no idea how to quantify it in flow rate, etc, but seems pretty substantial at times. I will see what kind of summer temps I end up with, my test hole was quite cool (never saw higher than 60. If that is the case the trout will be fine, but might be too cool for the Warmouth to spawn. On another note I had the idea to try to map the area for the topography of the underlying clay then build a dam based on that even if it was not by the pond.( basically building a clay dam in the woods under ground to increase the height of the water table and then dig the pond anywhere within that water table that that worked.) For now I am happy with the water table changes which have been less that 2 ft difference from high to low.