Ponds and Lakes
Lessons from Biologists
ponds and lakes and ponds
As Biologists, we invest our careers in designing and building the most natural appearing and functioning lakes and ponds possible. To accomplish this, we must understand how natural ponds and lakes were formed and how they function. On this page we share some of our knowledge with confidence that others will use this information to better appreciate our natural lakes and help take care of them.
We get many questions from people who would just like to learn a little more about the ponds and lakes where they go to recreate and enjoy life. We thought it was a good idea to create a place to help people understand the needs of these lakes and ponds so they can help preserve them for future generations to enjoy.
WHAT'S THE DIFFERENCE BETWEEN A LAKE AND A POND
Maybe the most asked question is: "what is the difference between a pond and a lake?" This question seems to have been debated forever. It will always depend on where you live and who you talk to, but we did sit down and develop a way for people to tell the difference. All it takes is a bit of observation to answer a few questions in our Rate-a-Lake Key.
RATE a LAKE
|Answer these questions to score your pond or lake
|Rooted plants grow to near the middle of the pond
|Roughly the same water temperature top to bottom
|Deep water is much colder than surface during summer
|Waves taller than 12 inches are common during storms*
|Outlet or feeder stream is wider than 15 feet
|Maximum Depth is greater than 20 feet
The scores will range from zero to ten. If the body of water scores a 5 or higher, it's a lake. Scores of 4 and lower are ponds. This is our very own rating system. Other people might not agree, but we have considered many forms of lakes that defy over simplified definitions of lakes (such as depth and plant growth) when we developed this system. We will talk about the types of lakes later. NOTE: * You don't need to wait for a storm to see the waves. If there is a beach, there were waves.
There are a couple of important exceptions to this rule, however. If you live in the New England region of the United States, your lake may actually be what New Englanders call a "Great Pond". We have heard a Great Pond needs to be at least ten acres to qualify. Some Great Ponds are actually large lakes by most people's standards.
If you live in Scotland, you have no lakes at all. What you have are called Lochs. We think the word Loch may be some Gaelic word for a lake with a big slimy monster swimming in it, but we aren't sure.
For some reason, if you live out west in the United States, any old puddle up in the mountains is called a lake. We suppose that's because any time you have to hike that hard to get to a pond in the mountains, it deserves to be called a lake.
ORIGINS OF LAKES and PONDS
Now that you have a rough idea of the difference between a pond and a lake, the next question is how did it get there?
Humans have lots of types of bulldozers and backhoes to build ponds and lakes with, but nature is the ultimate pond and lake builder. A huge bulldozer looks like a flea next to a glacier that is slowly carving and grinding away the land to form a lake. Some of the world's largest lakes, such as the Great Lakes in the United States, were formed from glaciers carving through the earth.
Glaciers carving down the side of a mountain will form large piles of debris which are called Moraines. Moraine Lakes form behind these debris piles.
Chunks of glaciers can also fall off the main glacier. When the climate warms enough to melt the ice, a Kettle Lake will form where the former ice was liquified.
Not all ponds need to be big. While a bulldozer and a backhoe may build big ponds, a person with a strong back and a hoe can build a small or even a tiny pond. You can build your own pond even as small as a mud puddle. Many people enjoy small ponds in their yards.
Nature may have the ultimate small pond builder called a beaver. While beaver ponds are small by natural standards, they are plenty big enough for people and wildlife to enjoy.
While many lakes are formed slowly by glaciers, others are built very quickly. Landslides can take less than a minute to form a dam that will back up huge lakes if the landslide crosses an existing river. Large earthquakes can form ponds and lakes due to sudden down-shifts in valley floors.
Even a forest fire can form a lake. There is a lot written about how lake succession where a lake fills in and becomes a marsh. A fire can turn a marsh back into a lake when all the decomposing vegetation that fills the lake catches fire. The peat material formed from decomposing vegetation will still burn. It can burn hot enough to dry out the lake and burn it deeper than the marsh that existed before the fire. Some of these marsh lakes can alternate forms within a century which results in a dynamic equilibrium between marsh and lake. Just remember not all lakes are destined to become a forest. This is one way forest fires play a very important role in maintaining natural environments. This is also important in current time since wildfires have mostly been suppressed over the past century. This has caused some very productive and ecologically important shallow lakes to be turned into savannahs of emergent marshes that do not support nearly as much wildlife and habitat diversity. Quite often what is labeled as a marsh on modern maps, should be lakes if society allows nature to take its course.
Many lakes form slowly by moving one grain of sand at a time until a shallow lake basin forms. These are called Playa Lakes. They exist in very dry areas were the wind easily erodes the soil and sand. Playa lakes were a challenge to our Rate-a-Lake Key since they are more like a very large pond than other lakes. They are shallow; their temperature doesn't change much from top to bottom, and they usually are not fed or drained by a stream. They score as a lake because they can have tall waves during storms and a good sized playa lake will be deeper than twenty feet - but not always.
This same wind in a coastal sand dune area can form a pond quickly by blowing away loose sand.
Rivers can become lakes and lakes can become rivers when a river channel changes to isolate or abandon part of its former channel. These types of lakes are often called Oxbow Lakes since the part of the abandoned river channel is usually at a bend in the river.
Some of the most beautiful lakes were formed by volcanoes or volcanic action. Crater Lake in Oregon was called Mount Mazama until the mountain errupted about 7700 years ago and expelled so much rock and dust that the mountain simply collapsed.
A hot volcanic vent can come into contact with cool surface water to cause an explosion. The resulting crater is called a Maar. These can be some very pretty mountain lakes that give hints to their formation because they are fairly rounded in shape. Lava flows can also form lakes much like landslides will create a lake.
Here are the lakes that break the over-simplified lake definitions such as depth, temperature change in deep water or plants growing near the center of a body of water. The over simplified rules are broken so often that we will use an example of rule breaking lakes that exist within just 100 miles of each other in central Oregon.
Klamath Lake, Oregon is over 60,000 acres; it is a shallow lake that is about the same temperatures top to bottom and the only reason there are not plants growing in the middle of the lake is the presence of consistent blue-green algae blooms so thick that light does not reach the lake bottom. Blue-green "algae" are actually cyano-bacteria, but that is another lesson. Klamath Lake is formed in a graben which is land that is slowly sinking between two geologic faults. Another temporary graben lake in the region is called a desert since it is only a lake during wet periods.
Davis Lake, Oregon ranges between about 40 acres to over 3000 acres. Davis lake was formed by a lava flow that covered a meadow on Odell Creek. Davis lake does have plants near the middle of the lake. The reason the lake has such a huge range of size is there is a hole in the lava dam that drains most of the lake during drought conditions.
Klamath Marsh, Oregon is currently a marsh until society decides it is acceptable for the next forest fire to burn the peat in the lake in order to make the lake deeper. If this happens the lake will be over 10,000 acres. It was also a deeper lake about 8,000 years ago before a lahar (a volcanic avalanche) blocked the lake and the basin filled in to form the current marsh lake. So Klamath Marsh is a lake or a marsh depending on future public decision. The only reason it is called a marsh is that was its state when early European explorers discovered it early in the 19th century. Anyone care to vote for it to become a lake again?
If three lakes nearly next door to one another can break most of the "rules", then what do you think of those "rules"?
SECRETS OF LAKES and PONDS
Now that you have an idea if your water is a pond or a lake and you may have a few ideas of how it was formed, what should you do next? We are firm believers in the power of observation; we also believe in taking a break once in a while. People who are good observers and thinkers have become very successful because they have practiced the skill of seeing things, then thinking about them to solve problems. A pond is a great place for children to become curious and to develop their power of observation and critical thinking skills. You can practice this skill out by your pond.
We suggest you take a break and just go sit by your pond and enjoy it for a while. If you sit quietly we think you will begin to see some pretty incredible things start to happen. While animals may scurry away when you first sit down, if you stay there for a half hour or so, you will see all sorts of things poking their heads back out and carrying on their every day business of survival. Keep an eye on the shallow water. Fish will reappear. You may see a dragonfly crawl out of the pond during the summer months. Beaver and muskrat are common along ponds and streams. Mink and otter are seen along ponds and lakes that are rich in fish life. Crayfish, salamanders and newts will commonly crawl right along in front of you in the shallow water. Watch these animals. See if you can figure out what they are doing and why they are doing it.
Notice the plants along the pond edges and in the water. There are many shapes, textures and heights. Each of these plants is specialized for a specific area of the pond edge. Each plant serves some function to other plants and animals as well. See if you can notice any patterns to where certain types of plants are growing. See if the plants under the water look and feel any different from the tall plants that grow several feet above the pond surface. Ask yourself why these differences exist.
After stretching your patience as far as you can by sitting quietly, go ahead and touch. Reach into the pond and turn over a few rocks and sticks. See what is crawling on the "other side of the pond": the part of the pond life that lives down in the dark cracks between the rocks. A whole other world exists in the dark side of the ponds.
Some of the most biologically productive land on Earth is the wet land next to a pond, lake or stream. You will probably observe more species of plants and animals here than anywhere. Because of this richness of life, it is important to consider the long term health of these special places. It is also important to protect them because people love these sort of natural spots.
Some people will be tempted to take animals home from the pond. Do this only after spending several trips to the pond to observe all the aspects of the natural environment. Then if you really want to take that frog home, first build a bit of a puddle out in the yard and wait for it to begin to look like the pond where you want to get your frog. Do not be surprised if the frog beats you to your pond though! As the saying goes "if you build it, they will come". Animals are always on the lookout for new neighborhoods to move into. They are complimenting your pond if they think it is natural enough that they choose to move there. If nothing moves in, then you need to improve your habitat offering to the wild things.
PRESERVING LAKES and PONDS
Now that you understand more about where your pond came from and how valuable it is, you may be more interested in keeping your lake, pond or stream healthy. Ponds and Lakes are especially vulnerable to pollution; even more so than streams. Ponds and lakes are great big sponges for excess nutrients and pollution. They can also have a difficult time dealing with heavy loads of nutrients generated from areas of intense human use, such as cities.
Streams have the luxury of having a lot of oxygen which is necessary to break down excess vegetation and sludges formed by decaying plants. This is because many streams are constantly falling and tumbling which mixes oxygen from the atmosphere in with the water. Ponds and lakes are not so fortunate. During the long days of summer, a lake or pond will produce great quantities of oxygen because plants produce oxygen as a by-product of their growth, which is known as photosynthesis.
There is a price for this oxygen production in still waters. When the water cools, the sunny days of summer turn cloudy and when temperatures drop, plant growth starts to slow. Plants then begin to die-off during autumn. At this point all of the bacteria and fungi take over and try to clean up all this mess of plants. They need to breathe oxygen to clean up the dead plant material. All of the oxygen produced during summer is now rapidly being consumed. If this happens vigorously enough, an entire lake can run out of oxygen and die!
Plants need nutrients to grow. The best way to keep your lake or pond healthy is to keep the excess nutrients out of the water. This will allow the pond to clean itself without running out of oxygen because there is only a small fraction of the plants that have to be cleaned up. Generally speaking there are two very important nutrients that make a lake unhealthy when they cause the lake to produce too many plants. These are Nitrogen and Phosphorus. One or the other will become the limiting nutrient that will cause plant growth to stop when it is not in sufficient supply.
While there are generalities to be drawn as to which of these nutrients is the limiting nutrient on a regional basis, we have seen examples where the limiting nutrient shifts back and forth within a single stream/lake complex! It is best to consider both Nitrogen and Phosphorus due to the complexities of the natural environments. One always needs to look downstream to see the impact of your actions.
PROTECTING LAKES and PONDS
So how can you keep excess nutrients out of the pond lake or stream? An ounce of prevention is usually worth much more than a pound of cure in this case. The idea of creating stream, lake or pond buffer plantings around the edge of the water is very popular and productive. Preventing nutrients from flowing down storm sewers is a good way to prevent pollution. Washing a car at a car wash that recylces water instead of washing a car out on the street also helps.
Healthy water supplies during dry months also help keep the aquatic environment clean and healthy. Capturing rain water from a roof and running it through the small pond in your yard will help slow the surface runnoff and allow more water to seep into the ground. This ground water then emerges into the streams on a much more even basis instead of flooding the local lake. It also cools the water which provides a better environment for cold water fish like trout.
Reusing water also helps save the environment. Something as simple as not running the sink while you are brushing your teeth may seem like such a tiny factor, but if you measure that water, then multiply it by the number of people who live in your county, city or town, then multiply that by 365, you will begin to see the power of small acts. See if you can identify other ways to save water by reusing and conserving. As Biologists we are building a healthy business by creating wild habitats while saving water at the same time. We think you can do this too!
There are further resources in our web site to educate and help people live with and improve their local environments. Our Invasive Species Page discusses the positive aspects of encouraging native plants and animals.
At the end of each day, we smile because we have helped nature a little bit today. You can do the same thing at your home. We think you just might have fun doing it too!
If you scroll down a bit more, you will see a little cyber aquatic environment we created for your entertainment.
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