What Is the Difference Between a Pond and a Lake?
To most people, ponds are simply small freshwater bodies, and lakes are their larger counterparts. While this can be true, it isn’t always the case. Any expert on aquatic life will tell you that the differences between ponds and lakes are much more complex than sheer size. In fact, there are some ponds that are considerably larger than your average lake!
While the two terms are arbitrarily used, especially when natural features are given attractive names to appeal to investors (e.g. ‘Lake Cleary’ may sound more impressive than ‘Cleary Pond’), there are conventions that should help one determine which term is more appropriate.
To make matters more complicated, there are hardly any state laws that actually distinguish between these two water bodies. They are, indeed, both incomparably valuable in nature. But, their proper identification, coupled with an increased awareness of their differences, should aid in their conservation.
A quick deep dive into limnology, which is the study of inland water systems, is all it takes to gain a better understanding of how ponds and lakes differ. The way these basins are formed, their permanence, their maximum depth, their connectivity with other bodies of water, and their uniformity of conditions throughout the water column dictate their major differences. These differences, in turn, may support contrasting ecological features.
For purposes of proper land zoning, surface area and depth are the major criteria when distinguishing between lakes and ponds. In fact, datasets of the National Oceanic and Atmospheric Administration (NOAA) on lakes are limited to relatively large freshwater systems. Lakes can be defined as bodies of water that are dozens of acres large, whereas ponds are generally small and enclosed. This raises the issue of “lakes” that are wide-yet-shallow or of “ponds” that are small-but-deep. Now, what of those?
In case you are trying to resolve confusion or are in the throes of an argument with a co-lover of lacustrine life, here is a chart that outlines the major differences between ponds and lakes. These criteria are further explored (especially as there are exceptions) below. These values should only be used as a rough guide.
|Surface area||Usually a few acres at most||Generally greater than several acres|
|Depth||Up to ~20 feet||Tens to hundreds of feet|
|Connectivity||Not connected to other waterbodies||May be connected to other waterbodies|
|Light||Reaches the pond bottom||Does not reach the deepest part|
|Presence of plants||In all zones||Only in photic zone|
|General shape||Roughly defined||Irregular|
|Temperature||Uniform through water column||Not uniform through water column|
Depth & Thermal Stratification
Early limnologists saw that a major difference between deep and shallow bodies of water was the extent of thermal stratification in the water column. In shallow basins, where sunlight can penetrate into the deepest parts of the system, water conditions tend to be uniform. As the entire system is within a “photic zone”, i.e. its entirety is exposed to sunlight, photosynthetic organisms can colonize the benthos. As a result, ponds (which are shallower), tend to have densely planted bottoms.
In contrast, basins with deeper benthic zones may have a less uniform or “stratified” water column. As sunlight is unable to penetrate through to the deepest reaches, conditions in photic zones, subphotic zones, and aphotic zones are markedly different. Temperature and water pressure (which increases with depth) affect the density of water. As a result, the warmer, shallow, photic zone of the water column is unable to mix with the deeper, cooler, and darker zones.
Characteristics of each depth zone, including their unique communities of animals and plants, are markedly different. The less dense epilimnion, which refers to the warmer layer of water above the thermocline, consists of rich communities of photosynthetic primary producers along with the food webs that directly benefit from them. The denser hypolimnion, which is the colder layer on lake bottoms, contain communities that thrive in darkness and may rely on sinking organic matter and circulated nutrients to survive.
The Largest Pond
In terms of surface area, the presence of islands, and the irregularity of its outline, the largest pond in the world meets all the basic criteria to be rightfully distinguished as a lake. With a surface area of 8,533 acres, shouldn’t Great Pond be called “Great Lake” instead? Limnologists argue that this exception to the rule is a pond, as its average depth is just 21 feet (6.4 meters)!
Its maximum depth, which is 69 feet (21 meters), remains to be in the photic zone due to the water’s stellar visibility. Thus, the lack of thermal stratification makes it quite different from typical lake systems. Most of the pond bottom is generously covered in vegetation, which supports dozens of species of fish, waterfowl, reptiles, amphibians, and macroinvertebrates. As a result, the pond is now one of the most popular fishing and tourist destinations in Maine.
Great Pond’s history, which sheds light on how the construction of a dam influenced the significant expansion of the pond’s surface area, also contrasts the natural history of most lakes. This classic example clearly encapsulates the complex, and often initially imperceptible, differences between lakes and ponds.
The Connectivity of Lakes
The smallest lake in the world, Benxi Lake in China’s Liaoning Province, has a surface area of just 15 square meters. Arguably just as large and deep as many other manmade ponds, this clear lake fits practically all of the criteria that distinguish ponds from lakes. It is very different from most ponds, however, as it is directly linked to a subterranean river system and has a flow rate of about 20,000 tons of water per day!
Limnologists may define ponds as enclosed systems. Naturally formed ones may have been part of larger lake systems in the past, before the streams that connected basins to one another dried out completely. The Benxi Lake, with water endlessly gushing through it, is definitely far from enclosed. In fact, it is an important drainage fixture of the Benxi Water Cave National Park.
In terms of general connectivity, lakes can be completely isolated, serve as headwater systems (i.e. release water through stream outlets), or be drainage systems (receive and release water via stream inlets and outlets) in larger wetland zones. Conservationists and limnologists must look into the water systems to which lakes are linked. Given the well-connected nature of many natural lakes, their proper conservation requires highly adaptive and complex management practices that may involve protecting multiple types of ecosystems.
The Ever-Changing Nature of Lakes & Ponds
As freshwater systems are constantly changing, especially due to climate change, ponds won’t always be ponds and lakes won’t always be lakes. Natural transitions due to the directional flow and availability of water can cause a lake to be fragmented, eventually leading to the development of a wetland system with smaller ponds.
In the endless process of change, lakes and ponds are extremely difficult to split into well-defined categories. Even something as predictable as the seasons can change a “lake” into a “pond” (and vice versa) year after year, so we can only ever hope for scientifically accurate definitions of these two water bodies.
Maybe more technical terms have yet to be made so that the arbitrary and interchangeable usage of the words ‘lake’ and ‘pond’ can be put to rest. For now, we need to simply accept that there will always be exceptions to what we perceive as ponds versus lakes. What matters is that each of these aquatic systems is afforded ample protection based on their specific features and their ecological contributions to natural life.