Make sure you design the dam and spillway structures correctly. This requires careful consideration, and for larger lakes (more than 200 acre-feet of water), professional consultation is highly recommended. To budget expenses, a pond designer can estimate how much dirt must be moved to construct the dam and a core trench.
A core trench is an excavated trench in the foundation material under a dam in which special material, usually clay, is placed to reduce seepage. In order for the dam to impound and release excess water effectively, investigate the advantages and disadvantages of various primary and emergency spillway designs.
A primary spillway usually consists of a pipe of appropriate diameter to easily transport excess water through the dam during a “normal” rain event. These pipes usually pass through the dam’s center, releasing water into the lowest point downstream. Several primary spillway designs exist, ranging from surface-release drains to bottom-siphoning systems.
For fishing ponds, the bottom-release designs are considered more desirable because poorer quality water near the bottom is passed through while retaining higher quality surface water. Design emergency spillways to allow passage of flood waters (usually around the end of the dam) with care to avoid soil erosion.
Next, design your pond shoreline slopes for optimal use. Slopes of at least 2.5:1 ratio (2.5-feet drop per 1 foot from shore) are best to avoid large expanses of shallow water. Shallow water, less than 3 feet in depth, allows sunlight to penetrate to bottom sediments, which can encourage excessive aquatic plant growth. Steeper slopes can also position fish within easier casting distance of bank anglers. However, slopes should also depend on soil type and effort should be given to guard against erosion of steeply sloping banks.
The final planning stage should be devoted to including habitat improvement structures to be added prior to pond filling. Fish habitat can be added later, but is much easier before the pond fills with water. Check out the following article for more information concerning fish attraction and habitat structures.