Many reports of farm ponds leaking have surfaced this year. No one seems to know why those reports would be higher this year than in other years. However, Gary Steinhardt, Purdue University Extension soils specialist, says there are good reasons why farm ponds sometimes don't hold water.
The bottom line is that you just can't build a pond because you think it would be a nice spot to have one without investigating the soils first, he says. Many people make the mistake of not checking soils until after they build a pond and have problems, he adds.
Outwash soils, or soils formed on terraces leading up from a river flood plain to upland soils often have gravel somewhere relatively high in the profile. Even if you're a considerable distance from a river, you can still have outwash soils if it's a large stream or river, he notes. The gravel may be within 48 inches of the surface, or it may be deeper.
In the northern two-thirds of Indiana, one reason ponds don't hold water over time is that they may be built on these kinds of soils, Steinhardt says.
If there's gravel underneath at some point, water will move through the gravel and not stay put. Gravel or sand and gravel allow water to move to another location.
"Even on poorly drained soils that are classified as till soils without sand and gravel, there are sometimes what we call 'lenses' of sand deeper in the profile," he says. "If you build a pond in those kind of soils, they may leak also."
If you're determined to build a pond on that type of soil, lining the pond with clay, often called bentonite, usually will minimize leakage problems, he notes.
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The bigger issue comes in the southern third of Indiana, where many soils are built over limestone, sometimes at relatively shallow depths. Especially in areas where there are sinkholes and underground connected waterways, building a pond can be very tricky, if it's possible to build one at all, he says.
The irony is that these soils may have several inches of hard clay above the bedrock. "The problem is over time you get cracks and the ability for water to move downward into underground water channels makes it very hard to build ponds in those areas," he says.