The Mud Pond and High Water Tables

[Sangreaal]

Does anyone know the dynamics between mud ponds and a high water table? For instance, the top of the water table here is roughly 20ft in summer and ground level (or almost) in winter rainy season. How does this affect a pond situated thereon?

Marie

[bekko]

It depends on the soil type. With really tight clay soil, you can fill it with a pump and it will stay full. Well.... sort of - you would probably have to top it off on occasion. In sandy soil, the pond water level will be the same as the ground water table level.

Since you know that the ground water drops by 20 ft in summer (that's a huge drop) I suspect you have sandy pourous soils in your area. Your agriculture extension service will have access to soil maps in your area.

If you are considering constructing a mud pond, you may need to install a liner and place a layer of soil on top of the liner. The liner will cost at least 30-60 cents per square foot. There are also techniques for mixing bentonite into the soil to make it less pourous, but it seldom works very well.

In constructing the pond, you push soil from the center of the (future) pond to build surrounding berms. You may only have to excavate a foot or so to have enough soil for building the berms with enough left over to place a layer of soil back on top of the liner. With a high winter water table, you would want to keep some water in the pond through the winter to avid having the ground water lifting (floating) the liner.

A pond constructed in this way will be much easier to manage than a water table pond. You will be able to completely drain it via gravity and/or with a pump. Complete drainage is important for harvesting the fish and, equally important, for drying the sludge accumulations, getting rid of undesirable organisms, etc.

Water table ponds are notoriously difficult/impossible to properly manage. You cannot drain them. They will be too deep in the winter and too shallow (or dry) in the summer. A 25 foot deep pond would be really difficult to aerate.

-stevehopkins

[PapaBear]

If you were further south in the central valley you would probably have less trouble with a mud pond as there is a lot of hard pan (adobe clay)... but you would still have the water quality board to contend with. Sitting on top of an aquifer like you do makes a more alluvial soil type likely and rapid percolation rates tough to contend with.
Another information route you might consider would be local contractors you might be acquainted with. Anyone building homes in the country will know the percolation rates and that will give you an accurate picture of the subsoil types you have to contend with.

[Sangreaal]

I have plenty of clay in my soil. Plenty. And in testament to the water holding capabilities, my neighbor across the highway has a pond the size my reservoir will be that is filled with rain every year and manages to keep fairly full without pumping all the time to keep topped off. It is a berm type pond, the banks rather tall (if you walk up to it, you definately can't see over the top) with a 3:1 slope inside. No liner. Unfortunately this neighbor isn't the friendly sort so picking his brain about his pond is not a preferred option. (Mickey, you can see his pond across the highway and south to the next corner on Google Earth)

Marie

[bekko]

Sounds like you are in good shape then. Since berm ponds sort of sit on top of the ground rather than down in the ground, the high winter water table should not be much problem. Relying on rain to fill it sounds a little shakey though. Do you guys have wells?

-ste veh ok

[Sangreaal]

Quote: Originally Posted by bekko Sounds like you are in good shape then. Since berm ponds sort of sit on top of the ground rather than down in the ground, the high winter water table should not be much problem. Relying on rain to fill it sounds a little shakey though. Do you guys have wells? -ste veh ok

Cool.

I have a fantastic well with two pumps--one for both households and one ag pump for moving mass quantities of water, so I'm good to go on the well-water end of things.

I do flow through on every body of water I have--the ponds (2 liner ponds now) and the stock tanks. Mud is essential to hooves in summer, so the dribble through keeps the footing around the waterers soggy and runs off to settle thusly:



And this stays there all summer.

So because I have a high water table I can't successfully run ponds in the ground or partially so? Why?

Marie<------just gotta know

[bekko]

Well, it sort of depends on what you are going to do with the pond....

You can dig them down into the ground, but would only be able to drain and dry them in the summer when the water table is low. Summer is also when you most want fish in the pond.

Draining and drying the bottom does wonders for water quality and productivity. The organic matter is oxidized away and mineralized so there is less oxygen demand. The bottom will be much less anaerobic when the pond is refilled. And, when the pond is refilled there is a bloom (population explosion) of all sorts of creatures which provide natural forage for the fish.

However, if the plan is to keep fish and water in the pond all the time, then it doesn't matter that the pond is dug down into the ground. Over time (years) the pond ecosystem matures and the quality of natural forage may decline somewhat. If there are a lot of fish, they eat all the best stuff and less desirable forms become dominant. You have to be particularly careful about what types of aquatic plants take over.

You also need a plan for what to do with the spoil (the excavated soil) if the pond is dug down into the ground. You may be able to sell it as fill dirt or you may want to use the fill dirt yourself to build up another part of the property. They usually put the top soil aside somewhere when they start excavating so it can be put back on top of the fill dirt when the project is finished.

-ste veho

[Sangreaal]

Alrightie then! I understand! (major accomplishment, thanks Steve!)

Since there is no way to have a "dry" pond in winter here, and spring and summer are bad times to stand empty, what about a fall drying at harvest time? After a blistering summer of irrigating hundreds of acres of nuts and fruit orchards, the water table is at its lowest point--perhaps the best time to pump ponds dry if they're totally in the ground? And perhaps rotate this procedure from year to year so not every pond is emptied every year but every other year or two?

Knowing things like this aids me in the designing stages of this project and I really appreciate your input. Thanks for taking the time to explain everything to me.

Marie

[PapaBear]

If you plan to have multiple ponds anyway your thought of rotating them might not be a bad one. It is a common practice in wastewater treatment ponds to rotate seasonally for much the same reasons. I guess it really just comes down to space considerations, so if you have plenty why not?
Another thing to bear in mind about your water table is underground water flow. If you have that shallow of a water table in the winter/spring seasons there will be a great deal of water exchange within the ponds as the water table beneath you slowly migrates fresh water in and out of your ponds from beneath.
Location relative to water wells and subterranian water flow is also a factor to keep in mind. Percolation/migration from your ponds will introduce nitrates into the shallow aquifer. You want your ponds to be downstream from your water wells to prevent potential cross-contamination of your fresh water supply. The State is pretty narrow minded about anything that elevates nitrates in aquifers and you definitely don't want them up your @$$

[bekko]

Drying them in the autumn is fine too - if there is enough time.

What are you going to do with these ponds Marie?

-stev ehop k