How Do Lakes Differ from Ponds?

Most people think of lakes as large bodies of water suitable for boating and other activities, while ponds are smaller and often found in backyards. It's easy to see why this can be confusing, ponds and lakes are both inland water bodies. But when it comes to ponds vs. lakes, size doesn’t matter. In fact, some ponds are larger than some lakes and vice versa.

How Lakes Differ from Ponds

The main differentiating factor that determines whether an inland body of water is a pond or a lake is depth. A deeper body of water has a different, more complex environment for aquatic life than a shallow one. There may never be an exact definition for ponds and lakes, so most scientists who study lakes and ponds focus on the differences between deep waterbodies and shallow ones.

Both the depth and surface area of a water body can be used to determine whether it is a pond or a lake. Ponds are generally shallower, and the entire area of a pond is what scientists call a photic zone, which means that sunlight penetrates through the shallow water to the bottom of the pond. This allows plants to grow at that bottom as well as on the surface. However, lakes are usually much deeper, and sunlight cannot reach the bottom in some places. This is called the aphotic zone, and since no sunlight penetrates to the bottom, no plants can grow there.

Neither phytoplankton nor algae can live in the aphotic or sunless zones at the bottom of lakes. This makes the ecosystem of a lake very different from that of ponds, as these aphotic areas are populated solely by carnivorous organisms. In the shallower water found in ponds, the ecosystem is more consistent than that of lakes and may support rooted plants, pond weeds, phytoplankton, and algae.

Wave action is another difference between ponds and lakes. The waves in ponds are generally smaller than the waves in lakes. A 12-inch high wave would be considered small. In addition, the water in ponds tends to be the same temperature throughout, while since lakes have deep areas, the water temperature can vary.
Here’s a quick test for whether or not an inland waterbody is a pond or a lake:

• Does sunlight penetrate the entire waterbody?
• Does it have waves that are smaller than 12 inches?
• Is the water temperature uniform throughout?

If the answer to these questions is yes, the water body is considered a pond, if the answer no, it is considered a lake.

What’s in a Name: Ponds vs. Lakes

This is where it can sometimes get confusing. Some bodies of water are called lakes when they may, by definition, actually be ponds. This happens because someone chose a term and used it in the name. It’s as simple as that. It’s easy to see why, since lakes tend to be larger and deeper, a large pond may have been mistakenly named a lake, and vice versa for smaller lakes.

How Lakes Differ from Rivers

Lakes are stationary bodies of water, while rivers are distinguished from lakes by fast-moving currents. While these distinctions seem clear, the differences become more subtle in areas where rivers are wide, and the current slows in a way that the river may resemble a lake. In addition, a river may form a lake such as oxbow lakes if a portion of the river is geologically separated from the river’s main path over time.

However, some lakes do move, they just move slowly—so slowly that it can take generations for them to move. Below are some key differences between lakes and rivers.

• Lakes are generally stationary, and rivers are generally fast-moving.
• Lakes are fed by canals, streams, and rivers, while rivers are fed by rain and other precipitation.
• Lakes can be natural or man-made, while rivers are natural water bodies.
• Lakes are inland water bodies surround by land, rivers move along their banks.
• Lakes are generally not associated with the ocean or sea, while rivers run toward the sea, where they empty themselves out.

So, while lakes are large, fairly deep bodies of water, they don’t have currents. Rivers flow constantly and have currents.

Freshwater Lake vs. Saline Lake

Most of the lakes you’ll see are freshwater lakes, but some lakes are very salty. These lakes are called saline lakes. To be sure, freshwater lakes can have minute amounts, less than 1-3 g/L, of dissolved salt in them. Saline lakes, on the other hand, usually have between 3 and 300 g/L dissolved salt in them.

Saline lakes are generally found in dry environments where water only leaves lakes by means of evaporation or by seeping into the ground. As evaporation occurs, salts and other chemicals become concentrated in the water over time.

Although the majority of freshwater rivers and lakes drain into the ocean, saline lakes are created when they are the endpoint of the river’s flow. These lakes are called endorheic or terminal and are often called inland seas. These inland seas usually form when they are at the lowest point of the landscape and can be found in basins. These lakes are not that common, which is why most of them are very well-known, such as the Dead Sea in Isreal/Jordan, Mono Lake in California, the Great Salt Lake in Utah, and the Caspian Sea in Eurasia.

The Dead Sea was named because it thought that nothing could live in it, and although it is true that no fish live in this saline lake, some bacteria and algae can survive. In contrast, the Great Salt Lake in Utah is an important habitat for many organisms, including brine shrimp and other crustaceans. The shores of some saline lakes also provide valuable breeding territory and habitat for waterfowl and shorebirds.

Best Way to Keep Lakes Healthy

Lakes are often attractive and valuable features for the communities that surround them. For this reason, it is important to keep them healthy.

Create a Buffer of Native Plants

Creating and maintaining a buffer of native plants is one of the best ways to keep a lake healthy. Shoreline plants are a natural filtration system for the sediment and chemicals found in runoff, over food and shelter to wildlife and fish, and can prevent or slow erosion of the shoreline.
In addition, shade from shrubs and trees help keep the lake cool and oxygen-rich while keeping unwanted aquatic plants from taking over. In cases where the natural plant cover around a lake has been damaged or removed, replanting and maintaining a buffer can help improve the health of the lake.

The ideal plant buffer should be 20 feet wide or more and include a variety of native shrubs, trees, and groundcovers. Keeping walkways and pathways narrow will help minimize negative shoreline impacts. A company that specializes in lake management can help develop a plan with native plants that will help keep lakes healthy.

Keep Landscaping Chemicals Out of Lakes

Pesticides and fertilizers may seem like easy fixes for gardens and lawns, but they can create long-term problems for the health of a lake. They are often carried by rain and wind from gardens and lawns right into lakes, where they significantly impact the aquatic life. Reducing how much pesticide is used can protect lakes and make them a healthier environment for wildlife, fish, and people.

The aquatic herbicides that lake management companies use are not the same as those used by landscapers and are safe for use in ponds. In fact, all of the aquatic herbicides that are used by lake management companies should be licensed by the EPA for aquatic application to ensure they’re not harmful to the waterway.

Chemical fertilizers, especially ones that contain phosphorus, can stimulate the overgrowth of plants in the lake. The nutrients are easily washed from the lawn into the lake, where it becomes a food source for aquatic plants and can cause a harmful and unsightly algal bloom. Using organic fertilizers made of composted animal manure, composted food, and garden waste, and commercially made organic soil additives are better options. They slowly break down and improve garden and lawn soils. Also, rather than fertilizing on a set schedule, only fertilize when the garden or lawn needs it.

Maintaining a buffer of shoreline plants and making sure only herbicides safe for use in ponds get in the water bodies will help keep ponds and lakes healthy and thriving. Contacting a lake management company can help put you on the right path.