Pond Boss Forums Thread Like Summary - Silly newb question

We just bought 90 acres and are looking to build a pond. Been reading up a lot and had a question. If a 1/2 acre pond is built on flat ground, what is the purpose of the dam? And does it only go on one side?

Firstly you want to determine the type of subsoil and see how much compactable clay is present. If there is good clay within 4 to 6ft of the surface then the pond will not be a water table pond. Loose sandy soil usually results in a water table pond where the water level goes up and down during the seasons; high when wet and low when dry. I've seen water level in water table ponds in NW Ohio go up and down 5-7ft (2m).

A lot of ponds in Ohio are dug ponds on fairly flat clay based ground. A good dug pond is not just a dug hole. The topsoil is removed 8 ft wider than the final size until good clay is reached. Then the pond bottom basin is dug out and compacted with sheepfoot rollers, not by bull dozers because bull dozers are not good soil compactors. Then the deep dug out clay is layered in 4"-6" "lifts" around the 8 ft wide rim as a band around the outside edge and compacted with the sheepsfoot roller. Excess dirt from creating a deep pond can be use to create a sloping watershed to help fill the pond during wet periods. This creates a well sealed all clay lined pond basin that if done correctly will have minimal leakage. Once the pond fills there is enough rain to keep the pond filled year round with water evaporation loss and seepage of 12"-20" each year. If runoff from building roofs is run into the pond the pond stays full. Annual precipitation in northern US and eastern Canada is usually more than 2ft.

For a water table pond just a simple hole is dug out in the porous ground and ground water seepage determines the water level.

A pond in Canada should be at least 16 to 22 ft deep to minimize winter fish kills due to extended snow cover that usually kills the fish in shallow 8 to 12 ft deep northern ponds.