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Ponds and lakes

By Ranger Steve Mueller

By Ranger Steve Mueller

What defines a pond verses a lake? A pond can actually have a larger surface area than a lake. Ponds might be deep enough to extend below the water table so they can have water throughout the year. Vernal ponds do not extend below the water table so they normally lose standing water during the summer. They often lack water during fall and winter but might remain damp. They are important hibernating substrates for amphibians.

A water table is the upper level where water saturates spaces between rock particles. Depending on the crumbled debris, the water filled space could be between clay, silt, sand, gravel, cobbles, or larger rocks. The particles names mentioned are determined by size instead of rock or mineral composition.

We drill wells into groundwater for private homes and cities. Some cities lay pipes that run from a Great Lake to cities to draw large quantities of water. Many communities draw water from rivers. It does not matter whether the water comes from a Great Lake, river, or from drilling below the water table, the water is supplied from below water table with some exceptions. In parts of country water is so deep or solid bedrock underlies the area preventing wells. There water is captured from roofs and stored in cisterns if river water is not unavailable. 

Groundwater filling the Great Lakes first arrives as rain or snow falling directly into the lake or comes by rain or snow percolating through soil particles to a depth where it saturates spaces between the crumbled rocks. It then flows slowly to one of the Great Lakes in our part of the country. Groundwater moves towards the Great Lakes and flows through depressions deep enough to create lakes or ponds. The shoreline is at the water table.

Light penetrates to the bottom of ponds and is a key factor separating them from lakes. Lakes are deep enough that light diminishes to a point where it cannot support photosynthesis. This is not an absolute determining factor but is the primary one separating ponds from lakes. Usually plants can grow across the entire bottom of a pond and this is normally impossible in a lake. 

The amount of suspended dirt particles and even plants in a body of water determine how deep light can penetrate so a pond is normally defined by how deep light extends during the clearest portion of the year.

A thermocline will develop in a lake at a point where light cannot penetrate. It is a layer where the water above it is warmed and circulates separately from colder water below the thermocline. Warm water cannot hold as much oxygen and might become dangerously low causing death for some species. Cold water below the thermocline can hold more oxygen but because it does not mix with the water above, and it can become oxygen depleted causing fish suffocation. For this reason fish sometimes concentrate at the thermocline to breath. 

These are not all the factors involved in fish location so it will be good to visit with experienced anglers. Water flowing into lakes and ponds from surface streams is a source of oxygen rich water that concentrates fish. Plants and algae growing above the thermocline release oxygen during photosynthesis allowing fish to breath. If the plants and algae become too abundant, they can consume oxygen during the night causing fish to die of what is referred to as “summer kill.”

Nature niche survival for fish depends on each species unique needs. Trout need more oxygen than panfish but this article is about defining ponds and lakes. Generally lakes are too deep for light to penetrate to the bottom while ponds have light reaching the bottom. A pond can actually have a larger surface area and look bigger than a lake. Visit Chrishaven Lake at the Howard Christensen Nature Center to see a lake smaller than many ponds. 

A heavy black and white disk can be lowered into the water to see the point where it disappears. If it is a pond the disk should rest on the bottom without disappearing. Remember the amount of suspended material could prevent light from reaching a pond’s bottom during some portions of the year. Hard and fast rules are seldom the only factor for separating ponds and lakes.

Natural history questions or topic suggestions can be directed to Ranger Steve (Mueller) at odybrook@chartermi.net – Ody Brook Nature Sanctuary, 13010 Northland Dr. Cedar Springs, MI 49319 or call 616-696-1753.

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