Pond Construction and Location

Pond Construction

by Neil Shelton

Adding a farm pond to your property is probably the best thing you can do, short of building or drilling a well, to enhance the appraised value of your land, but the potential benefits to the landowner are far too valuable to express in terms of mere money.  If you have the right soil and location, you can provide yourself and your great-grandkids with food, livestock water, recreation and beauty for lifetimes to come.

On the other hand, if your location isn’t right, you’ll be wasting machine-hire which can run $75 to $150 per hour while destroying part of the ecology of your place in the balance, so you’ll want to check your site carefully before you proceed.

Soil Quality:

The most important aspect you need to consider is that of your soil’s characteristics.

In order for your pond to hold water, your soil needs to contain enough clay.   To test this, dig a hole down through the brown or black top-soil into the sub-soil, which will be yellow, grey or red in most locales.  Once you’ve dug down that far, pick up samples and squeeze the soil in your hands.  If it forms a firm ball that doesn’t crumble easily, then this will make good material for your dam core.  If the ball crumbles easily, then you’d probably be better off spending your pond-building money on something else.

Topography:

Obviously, you want a location where you can build the smallest dam that will do the job so an area where the topography forms as much of the sides of your pond as possible is best.  You also want the basin to be as wide and as flat as can be had.  Try to keep your dam under twenty feet high, so as to keep costs down.  Once you’ve flooded the area, you’ll want there to be enough water depth to retard weed-growth.

When evaluating potential pond sites, look carefully at the drainage area above your proposed pond.  If the slope is fairly gentle, then all you’ll need is sod growing on your spillway, but if the watershed area is steep and large enough, it will require concrete covering the spillway to stop erosion during heavy rains.

Do NOT attempt to dam a flowing stream unless you are prepared to utilize prodigious amounts of concrete.  Continuously flowing water, even a small amount, can cause massive erosion in only a short time, and small streams can become large torrents after a hard rain.  At any rate, if fish production is important to you, avoid building on any spring or stream that will cause the water to continuously flow over the spillway as this will bring problems of silt accumulation and weed control.  Also, spring-water flowing into the pond may lower the water temperature enough to hamper good fish production and growth.

 

Drainage Area:

The size of the drainage area is also critical.  Most authorities suggest that the ratio of watershed area to pond surface area be about 10-15 to 1 if fish production is of prime importance.  (If the pond is to be used for irrigation, or watering large numbers of animals, add more space accordingly to the drainage field.)

Avoid sites that drain barnyards, septic fields or roadways for obvious reasons.

You can boost your drainage area with the use of diversion ditches, but these should be used judiciously.  It’s more difficult to maintain a sod cover in many situations, especially at the ends of the ditch, and silt accumulation and erosion can quickly develop.

Pond Construction:

The machine of choice for pond-building is the bulldozer, although track loaders and even some wheel-loaders are used.  Most custom machine operators will charge from $75 to $150 per hour for a bulldozer, depending on the size of the machine.  In my area the typical machine is the Caterpillar D6 and the typical price is $100 per hour.

While this can vary broadly depending on all the variables, one eight-hour day should get you a small pond, two days a good-sized one, and four or five days ought to yield something in the small-lake category (one-acre plus).

The first step is to have the dozer clear away everything, including trees, stumps, roots and sod from the pond site and the “borrow” area where you’ll be taking out material to add to the dam core.

When that’s done, you need to stake off the dam site, and remove the topsoil down to well within the subsoil.  Push the top-soil aside for later use.

Also remove and stockpile the topsoil from the borrow area.   Ideally, you’ll leave one stockpile of topsoil below the dam and one above it.

Once the topsoil has been removed, excavate a trench directly under where the dam is to be.  (See Figure 23)  This trench, or “key”, should span the entire length of the dam and up the adjoining hillsides to the height of the spillway.

If you want to use the pond for stock watering, it’s strongly recommended that you run a pipe from inside the pond out to a watering trough downhill from the pond.   If you want to add a water-tank supply, next dig a ditch perpendicular to the core trench or “cut-off” for the supply pipe.   Remember that the ditch should be below the frost-line when it emerges from under the dam and the pipe used should be at least 1½ inches in diameter.  This ditch provides a good place to put a drain pipe in your pond, a handy thing to have as you may want to completely drain the pond on infrequent occasions.  Use a six or eight-inch pipe for this.

When the pipes are in place, it’s time to start building up the dam.  Use the best clay for the core, the next best for the front (water) side of the dam and what’s left for the back side.  Note again Figure 23: the front side of the dam should be at a 3:1 slope and the back side at a 2:1 slope; steeper than that, and you’ll have problems with erosion.

The finished dam should be about three feet higher than the floor of the spillway, and at minimum eight feet wide at the top, but make it wider if you’re able, as it is extremely handy to be able to drive a tractor or pick-up along the crest of the dam.  Twelve-foot widths, or wider, are recommended.

Spillway Construction

If your dam is going to fail, it will most likely do so at the spillway, so mind how your spillway is constructed.

Above all, the spillway needs to be level at its mouth.  Ideally, only a very shallow stream of water should move across the spillway so fish don’t swim out during heavy rains.  Make sure the spillway is wide enough to keep this stream at three inches or shallower, and so long and gently-sloping that the water moves as slowly as possible, again to discourage erosion.

Depending on the amount of watershed and the weather, even a good-sized pond may fill up with water in just one heavy storm, or it may take weeks or months.  When it’s half full or so, you can begin looking for fish to stock your new pond.  In this area, fingerlings become available from the feed stores in the late spring to summer.