watershed wisdom

Collected nuggets of watershed wisdom from BRCA Executive Director Peter Kallin:

• Watershed Wisdom - Slow the Flow (March 2008)
• Trees (February 2008)
• Watersheds 101 (January 2008)
• Watershed Wisdom - Greetings (May 25, 2007)
• What is a "Watershed," anyway, and why should I care? (June 8, 2007)
• Mother Nature's Watershed (June 15, 2007)
• Mother Nature's Wastewater Treatment Plant (June 29, 2007)
• An Ounce of Prevention (July 6, 2007)
• Ancient Wisdom (July 13, 2007)
• Lake processes (July 20, 2007)
• Why phosphorous? (July 27, 2007)
• More about phosphorous (August 3, 2007)
• A Laker's Dozen (August 10, 2007)
• Boats and Water Quality (August 17, 2007)
• The importance of dihydrogen monoxide (August 24, 2007)
• The Leaky Bucket (August 31, 2007)

Watershed Wisdom - Greetings

Greetings to the greater Belgrade Lakes Community!

As the new Executive Director of the Belgrade Regional Conservation Alliance (BRCA), I am excited to have the opportunity to work with the extensive network of citizen volunteers that comprise the various lake associations and other conservation groups that make up our alliance. Together, we can accomplish our mission of preserving, protecting, studying, and promoting the natural resources of the Belgrade Lakes Watershed. For my part, I am looking forward to building and expanding on the programs that my predecessor, Mike Little, ran so capably for so many years, including writing a weekly "Watershed Wisdom" column for Summertime in the Belgrades.

I am a big admirer of the 20^th century conservationist, Aldo Leopold, author of A Sand County Almanac, a collection of essays on nature that I highly recommend to anyone who hasn't read it yet. In his final essay, Leopold describes his concept of "the land-community" that includes all soils, waters, plants, and animals in the community. To ensure the survival of this community, he calls for a "land ethic (that) changes the role of Homo sapiens from conqueror of the land-community to plain member and citizen of it. It implies respect for his fellow-members and also respect for the community as such."

Aldo Leopold passed on this respect for nature and community to his son, Luna, who became a prominent hydrologist. According to Luna Leopold, "Water is the most critical resource issue of our lifetime and our children's lifetimes. The health of our waters is the principal measure of how we live on the land." During my tenure as BRCA Executive Director, I hope to help the greater Belgrade Lakes community to become more connected to and respectful of "the land-community" that comprises the Belgrade Lakes Region. It is a special place and we, the current members of that land-community, need to make sure it stays that way for future generations. I hope to use this column to help make everyone aware of things they can do, or in some cases, not do, to make that happen.

If you are not yet a member of the BRCA or one of our lake associations, please consider joining and becoming part of that process. If you are in Belgrade Lakes Village, please stop by the BRCA Office and introduce yourself. We are in the same building as the Post Office. We have a lot of good information about the natural resources of this region, including maps of the nearby hiking trails and surveys of the lakes.

What is a "Watershed," anyway, and why should I care?

The goal of this week's column is to make sure readers understand what a watershed is, and most importantly, recognize that every one of us lives in a watershed, and how we live has an effect on water quality.

In 2003, the Maine Department of Environmental Protection (DEP) conducted a state-wide survey to assess Maine residents' knowledge about various environmental issues involving watersheds and stormwater. The poll showed that only 21% of those surveyed knew what a watershed was and that they lived in one. The survey also showed that Mainers had very little knowledge about stormwater and where it went, with 64% selecting the option "I have no idea."

When most people hear the word, "watershed," they immediately think of water bodies such as lakes, rivers, or streams. But a watershed actually refers to the land from which water flows into a particular water body. Think of it as the land "shedding" water like feathers shed water from a duck's back. When it rains, some of the water evaporates quickly back into the atmosphere, some infiltrates into porous soils and becomes groundwater, and the rest runs off as "stormwater." As to where the stormwater goes, I'll let you in on a secret- it flows downhill until it can't flow down any more and then pools up or infiltrates into the ground. In steep rocky areas like the Belgrade Lakes area, less infiltrates and more runs quickly down the hill, perhaps in a roadside ditch that dumps to a small stream to a larger one and then to the Belgrade Lakes. As the water flows across the surface of the land, it picks up dirt and other pollutants such as oil and grease from the roads.

Some water bodies have very large watersheds- the Mississippi watershed comprises approximately half the area of the Continental United States. The Belgrade Lakes Watershed is approximately 180 square miles with portions of 13 different municipalities in three different counties. This illustrates another important point about watersheds- they are determined entirely by Mother Nature's boundaries when she laid down the topography, not by Man's artificial municipal boundaries. This means that many different political groups need to cooperate to control the land use within a watershed.

The bottom line- everyone lives in a watershed. And how we live determines the quality of the water that drains from our watershed. More on that in future columns.

Mother Nature's Watershed

Last week I talked about what a watershed is and why we should care. The key point from that column is that water quality is directly dependant on land use within the watershed and the way the stormwater washes across it. Mother Nature's basic watershed design is a wonder of efficiency, with forests covering the hills and vegetated wetland buffers protecting the lakes and streams.

As anyone who has ever taken shelter under a tree during a rainstorm knows, trees do a great job of protecting the land under them. When the large raindrops hit the vegetation, they are broken up into many little droplets that continue to fall towards the ground, breaking up into ever smaller droplets as they hit more layers of vegetation. The large surface area of the leaves and small branches becomes coated with water that never reaches the ground, a process hydrologists call "interception." The water that continues to fall to the ground ends up as a fine mist, or slow moving drops that drip off the lower parts of the tree. This moisture falls gently onto a thick spongy "duff layer" of decomposing leaves and pine needles that comprises the forest floor, soaking in slowly. As the runoff filters slowly through the forest floor, it continues to soak into the sediments below where it enters the groundwater table. Except in very large rain events, very little stormwater actually runs off from a forest.

Contrast this with rain that falls on a plowed field, paved surface, or a dusty camp road. The raindrop hits the ground at high speed, with enough kinetic energy to erode the surface of the soil and splatter up muddy water. This water begins to puddle up and move down the hill, carrying dirt, manure, or other pollutants such as oil or grease along with it. If the surface topography is steep, the stormwater gains momentum and continues to erode, picking up an even higher pollutant load. Typically the stormwater from these developed areas is routed rapidly through ditches and pipes directly to the nearest stream, river, or lake. The turbulent motion generates kinetic energy that allows the flowing water to carry a large load of suspended sediments. When the polluted water eventually reaches a large pond or lake, the velocity will slow and the suspended sediment will settle out. The coarser sediments settle rapidly near the shore but the finer sediments (and attached pollutants) move out into the lake, creating turbidity, or cloudiness. These fine sediments settle very slowly, spreading pollutants to the deepest portions of the lake.

Under Mother Nature's system, thanks to the trees and surrounding vegetation, there is much less water flowing across the land surface towards the water. This water continues to be slowed and filtered by vegetation and rarely develops enough momentum to carry a heavy sediment load. As the flowing water approaches a stream or lake, it typically flows into a heavily vegetated wetland buffer that acts as a large sponge to absorb the water and further slow the flows, allowing suspended sediments to settle. Some of the fine sediments adhere to the surface of the plant stems in the water column, a process known as "adsorption." The end result is that the water finally reaching the lake is clean and clear.

So, how do we protect our watershed and maintain high water quality? The answer is to mimic Mother Nature's system as much as possible. More on that in future columns. In the meantime, contact me at BRCA (495-6039) to find out about the LakeSmart Program.

Mother Nature's Wastewater Treatment Plant

Last week I talked about Mother Nature's watershed design and the importance of trees and wetland buffers in protecting lakes and streams. This week I'm going to expand a bit on the importance of wetlands, Mother Nature's Wastewater Treatment System.

Wetlands are typically transitional ecosystems- not quite dry enough to be an upland, but not quite wet enough to be a river or pond. They are what ecologists call an "ecotone," where both terrestrial and aquatic organisms coexist, or perhaps take turns existing at different times of the year. Not long ago, wetlands were looked upon with scorn as unusable land that had little economic value and provided breeding grounds for mosquitoes and other pests. In the 19^th Century the US had numerous laws and programs that actually encouraged the filling or draining of wetlands in order to "reclaim" land and over half the wetlands in the continental US were eventually destroyed.

In the 1930's duck hunters recognized that fewer wetlands meant fewer ducks, and ecologists began to recognize the critical importance of wetlands to water quality and breeding habitat for certain birds, fish, and amphibians. These diverse groups brought about changes in the laws and wetlands were given special protection by federal and state governments. A complex set of rules has evolved that defines wetlands legally based on the soils, plants, and hydrology and protects the areas in and around wetlands.

Wetlands purify water through the same processes that man-made wastewater treatment plants use- and then some. Photosynthesizing plants and algae take up nutrients and generate oxygen. The plant stems and planktonic (floating) algae cells take up metal contamination and sediment through adsorption and remove it from the water column. Wetland plants transport oxygen and other compounds to the root zone or "rhizosphere," providing sustenance to various bacteria that are the real workhorses of the system. These bacteria break down organic contaminants and take up additional nutrients. Through the process of "evapotranspiration" the plants take up water from their roots and release pure water to the atmosphere, where it recycles as rain. The water that is released is replaced by additional water flowing towards the roots, so the plant essentially acts as a pump to draw the dirty water through its zone of cleansing bacteria and sediments. Clean water leaving the wetland recharges groundwater aquifers or seeps slowly to nearby waterbodies.

Wetlands also act as sponges to store flood waters and release it slowly during drier periods. Small wetlands known as vernal pools provide critical habitat so frogs and salamanders can lay their eggs in fish-free waters. Shoreline wetlands provide erosion protection and shelter for juvenile fish. Accumulation of peat in bogs sequesters carbon, helping to reduce greenhouse gas accumulation. With all these critical functions, it is no wonder that a recent study concluded that wetlands are the most valuable ecosystems on the face of the planet, providing approximately $15 trillion worth of value world-wide. Clearly a resource well worth protecting!

Want to know more about wetlands? Stop in to visit me at BRCA or visit EPA's web site at: www.epa.gov/owow/wetlands.

An Ounce of Prevention

I have been discussing Mother Nature's watershed design and the importance of trees and wetland buffers in protecting lakes and streams. This week I'm going to introduce a human program that is designed to help protect watersheds based on Mother Nature's principles-Maine DEP's LakeSmart Program. This program is proactive in the sense that it is aimed at preventing degradation rather than remediating a badly damaged ecosystem. There is an old saying that "an ounce of prevention is worth a pound of cure." In terms of managing lake watersheds the expression should be "an ounce of prevention is worth a ton of cure."

Roads, camps, and houses built near the lakes disrupt Mother Nature's system and can bypass some of her protective buffer systems. Through normal every day activities, people introduce phosphorous and other contaminants into the watershed including road dust, fertilizers, pet waste, soaps, garbage, detergents, eroded soil, oil and grease from vehicles, septic effluent, grass clippings, raked leaves, and others too numerous to mention. Additionally, the creation of impervious surfaces such as roofs, driveways, and roads provides areas where stormwater runoff is concentrated and picks up speed while it rolls downhill. The kinetic energy of the flowing water exacerbates the situation by increasing erosion and transporting all the extra pollutants quickly down hill toward the lake. This can potentially increase the pollutant load to the lake a hundred fold or more compared to the undeveloped forest condition.

With smart design and a few simple management practices, the vast majority of this increased pollutant load can be prevented from reaching the lake. I will discuss some of these practices in a little more detail in future columns but they are all based on a few simple principles aimed at preventing pollution where possible, dispersing and slowing the flow of water as much as possible, taking advantage of any opportunities to infiltrate (soak into the ground) or filter (run through a vegetated buffer area) the runoff before it reaches the lake. And above all, don't dump anything directly into the lake.

To prevent pollution, make sure simple things like routine maintenance on your septic system or vehicles gets done. Don't drive around with oil leaks in your car or boat. A few drops of oil can contaminate hundreds of gallons of water. Upgrade your old two-stroke outboard to a newer four-stroke model. Don't fill your gas tanks in the boat-wherever possible, take them out, fill them carefully away from the water and carry them back to the boat.

Keep your property functioning as much like Mother Nature's system as possible. Don't let water run straight down your driveway toward the lake. Use berms, rubber razors or simply crown the road to divert the water off into the woods. Don't let runoff concentrate and pick up speed. Avoid bare soil- don't rake up the leaves and pine needles under the trees. Leave the natural duff layer in place. Don't cut your grass to the waters edge and then dump the clipping in the water. Maintain a good vegetated buffer along the waters edge. Mulch your walking paths and water access points to prevent erosion.

Maine DEP's LakeSmart Program will provide an assessment of your shorefront property in the following categories: 1) Road, driveway & parking areas; 2) Structures & septic systems; 3) Lawn, recreation, & footpaths; and, 4) Shorefront and beach area. For more information or to schedule an assist visit, please stop by the BRCA office or call Jason Bulay at 495-6039. See: www.maine.gov/dep/blwq/doclake/lakesmart/index.htm

Ancient Wisdom

I have been discussing Mother Nature's watershed design and the importance of maintaining upland forests and vegetated wetland buffers to protect water quality. I have talked about the importance of responsible development to avoid excess stormwater runoff that can cause erosion and deplete groundwater supplies. These are not new ideas. Consider this observation from over 2000 years ago:

"There are mountains in Attica, which can now keep nothing but bees, but which were clothed, not so very long ago, with fine trees producing timber suitable for roofing the largest buildings….while the country produced boundless pasture for cattle. The annual supply of rainfall was not lost, as it is at present, through being allowed to flow over a denuded surface to the sea, but was received by the earth, in all its abundance, into her bosom where she stored it." Plato: Dialogue of Critias 360 B.C.E

Plato could just as easily be talking about modern day America. Cutting down forests in the uplands and clearing the native vegetation results in too much impervious surface, which in turn results in excess stormwater runoff. Instead of recharging the groundwater aquifers and filtering slowly into streams and lakes, this runoff flows quickly down the hills, resulting in flooding in the lowlands and excessive erosion.

The LakeSmart program I discussed last week emphasizes the importance of maintaining native vegetated buffers along the shorelines of our lakes, rivers, and streams. Over 500 years ago, Leonardo da Vinci gave the same advice: "The roots of the willows do not suffer the banks of the canals to be destroyed; and the branches of the willows, nourished during their passage through the thickness of the bank and then cut low, thicken every year and make shoots continually, and so you have a bank that has life and is of one substance."-Leonardo Da Vinci (14521519)

In future columns I will be discussing ways to take advantage of Mother Nature's built in systems and ways to modify man-made systems to mimic natural systems. If you are interested in exploring some of these ideas further, stop in to BRCA's office in Belgrades Lakes Village, next to the Post Office and I would be happy to chat with you.

Lake Processes

The Belgrade Lakes area is a special place, dominated by the 7 large lakes of the Belgrade Lakes chain (East Pond, North Pond, Salmon Lake and McGrath Pond, Great Pond, Long Pond, and Snow Pond/Messalonskee Lake) but also containing numerous smaller ponds, especially in the Kennebec Highlands. The State of Maine has over 6000 "great ponds" of over 10 acres. As Ship Bright of the Maine Lakes Conservancy Institute pointed out last week, these lakes bring in over $3 billion dollars per year to Maine's economy. It is incumbent on all of us to understand and protect these lakes. This week I will begin discussing how these lakes came into being and how they are evolving.

Maine residents take lakes for granted- we've always had lakes as part of our landscape. These lakes are here because of the last ice age when large masses of ice were moving across Maine in a southwesterly direction, gouging out the earth's surface and piling up rocks ahead of the ice. About 20,000 years ago, when the glaciers began to melt and recede, they left behind large chunks of ice in low points in the landscape. These ice chunks melted and formed Maine's lakes and ponds, most of which are elongated north to south along the glaciers' direction of movement at the peak of the ice age. In terms of geological time, lakes are transient phenomena. Once lakes are formed, Mother Nature begins to fill them back in. As water goes through the hydrologic cycle, it is evaporated from the lakes, becomes water vapor in the atmosphere, and then condenses first into clouds and then cloud droplets combining to form precipitation. This precipitation falls back to earth, eroding the earth's surface as it flows downhill, sometimes after melting in the spring. Over geological time scales, these erosion processes turn rock into soil but they also eventually fill in low points in the landscape including lakes and ponds.

This is why the southern states have very few lakes. Without the glaciers to reform large numbers of lakes every 50 thousand years or so, there are very few natural processes that form lakes. Beavers will dam streams or rivers to form ponds, volcanoes will form crater lakes (e.g., Crater Lake, OR), meandering rivers will occasionally split off an "oxbow" lake, and sometimes meteors will crash into the earth forming depressions (kettle lakes of NC) or tectonic plates will rise from the sea (Lake Okeechobee) or collide (Lake Tanganyika). But these are uncommon events. Generally speaking lakes in the southern US are actually impoundments formed by damming a river or stream. This is why southerners are especially fascinated by Maine's natural lakes.

Newly formed glacial lakes contain nothing but water. They are what limnologists (people who study lakes) call "oligotrophic" or nutrient poor (think Lake Superior). Water flowing towards the lake dissolves minerals from the rocks and picks up soil particles including nutrients such as nitrogen and phosphorous. Over time, as this water enters the lakes, the water in the lakes becomes enriched and can support aquatic plants and animals including fish. This natural enrichment process is known as "eutrophication." A little eutrophication is a natural and necessary part of a lake's life cycle. But like many things in life, too much of a good thing can be disastrous and lead to premature death or illness. I will be discussing how this process affects the health of the lakes in more detail in the next few columns.

Why Phosphorous?

Last week I talked about the origin of lakes and introduced the concept of "eutrophication," or nutrient enrichment. Even with fully intact upland forests and vegetated wetland buffers to control sediment erosion, a small amount of sediment and nutrients are going to enter the lake. This is a natural process and a certain level of nutrients is necessary to support aquatic life. The problem comes when nutrient loading exceeds what the lake really needs to maintain a healthy aquatic ecosystem. The situation is analogous to maintaining a healthy diet and active lifestyle. If you consistently overeat, you will gain weight and suffer other health problems including premature aging. To remain healthy, you need to limit your caloric input to what your metabolism requires. It is the same with lakes. A lake will normally exist in a relatively clean state for tens of thousands of years with the healthy nutrient loading provided by Mother Nature. But if the nutrient load is excessive, that clean stage of life (the stages limnologists refer to as "oligotrophic" or "mesotrophic") can be reduced to less than 100 years. To keep our lakes from premature aging, we need to put the lakes on a diet. Most freshwater water quality programs attempt to limit degradation of water quality by limiting phosphorous. This week I thought I would further discuss the process of eutrophication and explain the concept of a "limiting nutrient."

Aquatic ecosystems vary in complexity but are all based on a food chain that has phytoplankton and other plants at the bottom. Phytoplankton are minute floating plant cells that create biomass through the process of photosynthesis. Using energy from sunlight, algae form plant cells by combining carbon dioxide (CO2) and water (H2O) with some nitrogen (N) and phosphorous (P). In the 1950s, an oceanographer named Redfield studied marine algae and determined that on average they were comprised of carbon, nitrogen, and phosphorous in a C:N:P ratio of 106:16:1. For freshwater algae, the ratio is

113:15:1. This means that for every 113 molecules of carbon dioxide the plant uses, it needs 15 molecules of nitrogen and 1 molecule of phosphorous to create plant biomass. Since light, carbon dioxide and nitrogen are in ample supply in most freshwater systems, the amount of plant growth that can take place is limited by the amount of phosphorous available. Phosphorous is the "limiting nutrient" in the system. Think of a car manufacturer who needs a ton of steel and 4 tires to manufacture a car. Even with twenty tons of steel, if he only has four tires, he can only make one car until he gets more tires. He is limited by his tire supply. In the same way, the productivity of freshwater aquatic systems is generally limited by the amount of phosphorous available.

Phosphorous is not especially soluble in water so precipitation percolating or filtering through the soil will not dissolve much phosphorous even if it is relatively abundant in the soil, as it is around here. Most of the phosphorous in the soils is bound to iron minerals in the soil under normal oxygenated conditions. The key to controlling phosphorous is to keep the soil from being eroded and transported into the lake. In simple terms, erosion control equals phosphorous control.

In future columns I will be discussing ways to take advantage of Mother Nature's built in systems and ways to modify man-made systems to mimic natural systems to limit erosion and control phosphorous loading to the lakes.

More about Phosphorous

Last week I talked about the role of phosphorous in causing eutrophication (nutrient enrichment) of the lakes and introduced the concept of a limiting nutrient. Lakes are complex ecosystems and the phosphorous dynamics in lakes contribute to that complexity. This week I will try to shed a little light on that complexity and the difficulties in controlling phosphorous.

Phosphorous is a highly reactive chemical that is often involved in reactions where a lot of energy is transferred. For example, it is a primary component of military incendiary weapons and flares, fireworks, and matches. In living organisms it is used to transfer and store energy through reactions between ATP and ADP and a certain amount is necessary to support aquatic life. In aquatic systems, phosphorous can exist in several different states. Soluble reactive phosphorous (SRP) is dissolved within the water column, primarily in the form of orthophosphate ions, which are "bioavailable" in the sense they can be readily picked up living organisms and turned into organic matter. Organic phosphorous (OP) is phosphorous that is bound up into organic matter already and not bioavailable to another cell unless the first one dies and decomposes or is eaten and digested by another. Most of the rest of the phosphorous in aquatic systems is typically in particulate form, bound to suspended solids, primarily iron and clay minerals.

When phosphorous is in particulate form, it is not very bioavailable because the phosphorous is bound so strongly to the suspended minerals, especially iron oxide particles. Only a small amount of the phosphorous will dissolve into the water column before the solids settle out to the bottom. Under normal aerobic (plenty of oxygen in the water) conditions, the bioavailable phosphorous in the water column is constantly changing as some is washing in from streams and overland flow, some is being taken up by plants as they grow, some is entering the water from degrading organic material or overloaded septic tanks, and some is settling out to the bottom. The actual amount in the water column is the difference between what is coming in (inputs) and what is going out (outputs). Under these conditions it is relatively easy to control the phosphorous in the water column by limiting the inputs. As long as some is constantly leaving, the amount remaining in the water column will decrease. It's analogous to losing weight by going on a diet (limiting inputs) while making sure you do moderate exercise (outputs). This aerobic situation is typical in rivers and streams but lakes are usually more complex.

The most complicated situation for our lakes occurs in the summertime when the surface waters warm and the lake stratifies into a warm surface layer called the "epilimnion" and a colder, deeper layer called the "hypolimnion." I'll talk a little bit more about why this happens in future columns but anyone who swims in the lakes in the summer and dives down until the water suddenly changes temperature has experienced it first hand. Under these thermally stratified conditions, there is little mixing between the layers and the oxygen that is entering the lake from the atmosphere never makes it to the bottom of the lake. At the same time, organic matter continues to fall to the bottom and uses up oxygen as it decomposes. As a result, the bottom waters go anoxic (no oxygen). Under these conditions, the iron in the sediments is reduced from the ferric (+3) form, which is virtually insoluble to the ferrous (+2) form, which is highly soluble. When the iron dissolves, the phosphorous that had been bound up in the non bioavailable particulate state is suddenly released into the water column as bioavailable SRP. If a mixing event occurs such as a sudden cooling of the surface water or a strong wind that can cause upwelling, this bioavailable phosphorous is suddenly stirred into the upper epilimnion where it can trigger an algae bloom because the limiting nutrient is no longer limited. This is when East Pond or North Pond suddenly turns green or the swimmers in Great Pond start complaining about Gleotrichia. This phosphorous loading from the sediments is called "internal loading" and is more difficult to control. We will talk about some of these issues in future columns.

A Laker's Dozen

I have been attending a lot of lake association annual meetings lately and getting to talk with a lot of people concerned about the water quality in our lakes. At several of them I have been asked to provide a short list of things ordinary people can do to help the lakes. Here is a pretty good list that has been compiled by the Maine Congress of Lake Associations (Maine COLA), reproduced with their permission. They have a lot of good information and links at their web site: (www.mainecola.org). Hopefully my columns so far have given you a good understanding of why all these recommendations are important.

A Laker's Dozen

1. Always check boat, trailer and equipment for plant fragments before launch and after take-out.
2. Respect Shoreland Zone Regulations. Before making any change on your land, check with your town to see what's permitted and what's not in the shoreland: 250' of the lake and 75' of streams.
3. Control storm water run-off from buildings, paths, driveways and road. Check your property on a rainy day and fix run-off sites by planting vegetation or constructing swales to direct water flow away from the lake.
4. Cultivate a wooded buffer. Trees, shrubs and grasses slow the flow and filter soil and pollutants from rainwater before they end up in the lake.
5. Limit lawn size, mow less often, and don't rake duff within 75 feet of shore.
6. Limit fertilizer, herbicide and pesticide use. Long lasting residues in these chemicals can turn lakes green and harm aquatic life.
7. Don't stress the septic system. Inspect the system yearly. Pump the tank regularly. Systems 20 years and older should be inspected by a specialist. Use phosphorus-free cleaners, and detergents. Stagger laundry loads. Minimize water use. Don't put grease or toxics down the drain.
8. Construct docks and floats with lake-friendly materials. Choose cedar, cypress, plastic, or aluminum over wood that's pressure-treated with arsenic.
9. Dogs, humans and boats should never be washed in the lake!
10. Observe headway speed within 200 feet of shore. Boating in shallow water disturbs fish habitat and stirs up sediment.
11. When you replace a boat motor, choose a clean 4-stroke engine.
12. Preserve wildlife habitat on land and underwater. Lake shallows and shorelands are home to many native species and nurseries for young.
13. Support your local lake association and Maine COLA.

Copyright © 1999-2007 - Maine Congress of Lake Associations

Boats and Water Quality

Last week I presented a list of 13 simple things that people could do to help the lakes. About a third of those involved boats in one way or another. Because of the widespread use of boats on the lakes it is worth discussing some of the earlier suggestions in a little more depth and provide a little more information on the importance of some of those suggestions. Some of those suggestions are legal requirements of the Maine boating laws and others are common sense ways of minimizing the impact of your boat on the aquatic habitat of the lake.

Maine boating laws and regulations are enforced by the Department of Inland Fisheries and Wildlife on all inland waters and also by the U.S. Coast Guard on federally controlled waters. A complete copy (40+ pages) of the regulations is available at the following web site: http://www.maine.gov/ifw/laws_rules/boatlaws.htm. All boaters in Maine, including out of state visitors, are required to adhere to the regulations so I recommend everyone who operates a boat review the rules. As any judge will tell you, "Ignorance of the law is no excuse."

One rule that is often ignored is the requirement that boats generate no wake in the "Water Safety Zone," which is defined as any area within 200 feet of any shoreline, including islands. Operators must maintain "reasonable and prudent speed for existing conditions" at all times and must "consider the effect of the wash or wave created by their watercraft to waterfront piers, floats, or other property or shorelines." There are a number of harmful effects to the lake when this law is broken.

The size of the wake generated from a boat is a complex function of the size, speed, loading, and shape of the boat, as well as the distance from shore and water depth. The speed with which the wake travels through the water is also a function of water depth. As the wave approaches the shore, it increases in height and steepness and turns toward shallow water. This increases the erosive power of the wave. The size of the wake determines the destructive energy when the wave hits the shore- a 12-inch wave hits with five times the energy of a 6-inch wave. The actual damage to the shoreline depends on the nature of the shoreline material and how exposed it is. In a wide, open area which is routinely impacted by large wind generated waves, boat wakes make up a very small percentage of the total energy dissipated against the shoreline and cause relatively little damage. In narrower, more sheltered areas, boat wakes are a much larger source of erosion. One Minnesota DNR study assessed boat wakes as the source of 95% of the erosion in smaller channels.

Shoreline erosion degrades aquatic ecosystems by increasing sedimentation and turbidity (cloudiness), releasing nutrients into the water, and by direct destruction of shoreline habitat. This increases the likelihood of algal blooms and can result in loss of valuable shoreline land or lower property values.

Another practice that is very destructive of benthic (bottom) habitat is operating boats at high speed in shallow water. The vortices (spinning eddy currents) coming off the rotating prop stir up sediments from the bottom, tear up rooted vegetation, and generally disrupt the habitat for bottom dwelling creatures. Jet skis are even more destructive because of the high speed jets pointed downward. High speed boat operations should only be done in areas where the water is at least three feet deeper than the bottom of the prop. High speed boating operations in shallow water can also be hazardous to the health of your boat. I know at least one camp owner on the north end of Great Pond that has a large collection of old mangled props and pieces of props that have been claimed by the shallow rocks in front of his camp.

Always inspect your boat and trailer for hitch-hiking plants when you launch or recover your boat. I think most of the local boaters around here understand the threat of invasive species such as Milfoil, but the same is not always true for visitors. BRCA's courtesy boat inspectors and the volunteers from the various lake associations do a tremendous job in this area but they can't be at every ramp, every minute of the day. Individual boaters need to learn the process and self inspect. This should also include saying something when they see something amiss with an out of town boat for example. Launching a boat into Maine waters with an invasive plant on it is a violation of Title 12, Section 13068-A of the boating laws and could result in a $5000.00 fine for the boat owner.

Safe boating is an important part of enjoying the lakes. By using your head and following the rules, you can have fun on the lakes without being destructive. Just as a few aggressive drivers can cause accidents and destruction on the highways, so too can a few aggressive boat operators cause damage to the lakes. If you see a violation, report it to your local game warden or harbormaster, who have primary responsibility for enforcement. Any law enforcement officer can also enforce boating rules.

The importance of dihydrogen monoxide

This week we will get back to some basic lake science to give you a little background on why and how things happen in lakes and why it takes so long to improve water quality in a lake. It may sound obvious but what makes aquatic ecosystems possible is the unique chemistry and physics of dihydrogen monoxide or hydrogen oxide, more commonly known as water. Water has some unique qualities that we usually take for granted but which make life as we know it possible. It exists in solid (ice), liquid (water), and gas (water vapor) phases at normal ambient temperatures. This basic fact makes possible the hydrologic cycle that drives our weather and fills our lakes with water.

Water molecules are made up of two hydrogen atoms that are positively charged and an oxygen atom that is negatively charged. The hydrogen atoms are attached to the oxygen at an angle of about 105 degrees, which results in the surface charge of the molecule being unevenly distributed. This makes water a "polar" molecule that is a very powerful solvent. Known to chemists as the "universal solvent," water has the ability to dissolve at least some of almost anything. This means that it can easily dissolve things like oxygen, carbon dioxide and nutrients necessary for life. It also means water can dissolve contaminants from the soil and transport them to the nearest water body. The amount and complexity of salt in the oceans is testimony to water's ability to dissolve minerals from rocks.

Water's polarity also results in another property that drives many lake processes. Most substances increase in density uniformly as they cool and the solid phase of most materials is denser than the liquid phase. With water, the density increases as it cools but only until about 4^oC (~39^oF) when it reaches a maximum. At temperatures below that, the water molecules begin to align into a hexagonal structure held together by hydrogen bonds that freeze solid at 0^oC (32^oF). As a result, solid ice is lighter than liquid water and floats on top. This is the reason that our lakes freeze from the surface down instead of from the bottom up. If water were like most substances, with the solid phase denser than the liquid, lakes in Maine would freeze solid from the bottom up and there would be no refuge of liquid water in a lake for aquatic organisms to winter over without freezing solid.

The fact that water has a maximum density above freezing also results in "turnover" of the water in our lakes. In the fall, as air temperatures decrease, the warm water at the lake surface also cools. Because the cooler water is denser than the water below, it sinks until it reaches the level where it is no longer cooler than the surrounding water. This sinking water creates downward convective currents that both cool the water column and bring oxygen rich water from the surface to deeper depths. As the lake cools, eventually it reaches a point where the water is the same temperature (4^oC) and density throughout and is well oxygenated from top to bottom. Because it is of uniform density, there is little resistance to mixing and the lake mixes easily with wind or flowing water currents. Cold water can dissolve more oxygen than warm water so this is the time of year when oxygen in the water column is maximized. As the surface water continues to cool below 4^oC, the cooler water is less dense than the deeper water and the surface water stops mixing downward and eventually freezes, resulting in a protective insulating blanket that allows the rest of the lake to remain as liquid water through the winter.

In the spring, as the ice melts and the water warms, the lake again reaches a point where it is the same density throughout and easily mixed. Because of this, lakes in temperate regions like Maine turn over twice a year, in spring and fall. Limnologists (scientists who study lakes) call these types of lakes "dimictic" lakes. This turnover ensures that the entire water column gets well oxygenated at least twice a year. In other parts of the world, the temperatures don't get cold enough to turn over deep lakes. In these lakes, which limnologists call "meromictic," the deep waters become anoxic and there is a permanent "dead zone" in which poison gases such as hydrogen sulfide can build up. Occasionally an unusual event such as an earthquake will disturb the stratification and the lake will belch poison gas such as Lake Nyos in Cameroon did in 1986, causing nearly 1,800 deaths. Next time you find yourself feeling like our cold Maine winters are a problem, think about what the cold is doing to help turn over our lakes and keep them healthy.

The Leaky Bucket

In this, our final installment for the season, we will try to give you more insight into why and how things happen in lakes and especially why it takes so long to improve water quality in a lake compared to a river or stream. Rivers and streams flow continuously down hill and are constantly mixed, with the water at any particular location being continually replaced with new water from upstream. If a river or stream becomes contaminated, the basic technique is to stop the source of the contamination and then wait a few days and you have new fresh water from upstream. Once the water quality returns, the plants, aquatic insects and fish will return in reasonably short order.

Lakes take a lot longer to cure, especially large lakes. Most lakes have water flowing into them on a continuous basis from streams or groundwater and also have water flowing out via some type of outlet stream or river. There are some lakes, particularly in arid regions, where the water only leaves when it is evaporated. These lakes either become very salty (e.g., Great Salt Lake, Utah) or disappear completely if it hasn't rained for a while. Luckily our Maine lakes aren't like this. The water in our lakes gets replaced eventually.

The Belgrade Lakes all have flowing water entering them on average and a discharge stream, typically flowing over some type of dam that regulates flow. These lakes act like leaky buckets that have a notch cut in the side. As water is added to the bucket, it will fill to the level of the bottom of the notch. If you continue to add water to the bucket, the water will rise a bit (it will rise more if the notch is narrow, less if it is wide) but then fall to the level of the bottom of the notch if you add water at a rate slower than it can leak out. The actual level of water within the bucket is determined by the rate the water flows in and the size and shape of the notch in the side of the bucket.

Suppose someone dumps green food coloring into our bucket. How long will it take to flush the bucket clean by simply adding clean water and letting the green water flow out through the notch? Obviously it's going to take a lot longer if you have a big bucket and don't have much water flowing through it than if your bucket is small and has a lot of water flowing into it. This is the basic concept of what hydrologists call "flushing rate," which is directly related to "residence time."

Residence time is defined as the average amount of time that water entering the lake stays in the lake before it flows out of the lake. It is calculated by dividing the average volume of the lake by the annual flow going through the lake. If our lake holds 150 million cubic meters (M³) of water like Messalonskee Lake does, and the average annual flow is 240 million M³ per year, the average residence time is .625 years or roughly 7-1/2 months. The flushing rate is simply the inverse of the residence time which represents the average number of lake volumes that flow through the lake in a year. For Messalonskee, the flushing rate is about 1.6 flushes/yr.

Studies done by Colby College have estimated the following flushing rates for the Belgrade Lakes:

Of course natural lakes are much more complex than our simple bucket analogy and these rates assume the lakes are perfectly mixed, which our previous column showed is rarely the case. These flushing rates give a rough idea of how fast the lakes flush and are more accurate for a long, regularly shaped lake like Messalonskee that only has one deep area than for a large, irregularly shaped lake like Great Pond that has several deep basins and streams of various sizes coming into different coves.

In lakes like Great Pond that stratify, the surface waters flush more rapidly than the calculated flushing rate, while the deeper waters flush much more slowly because they are only really well mixed about twice a year. This means that if you are trying to remediate the high phosphorous levels in the deep holes, which are the biggest problem as we have previously discussed, it takes a long time to flush these areas. Where the average residence time for water in Great Pond is slightly less than 2 years, the residence time in some of the deep holes is probably more on the order of 20 years or more. This means that fixing lakes takes a lot longer than fixing a stream or river.

Hopefully these columns have provided you with some insight into lake processes and a better understanding of the issues involved in improving water quality. While waiting for your 2008 issue of "Summer in the Belgrades," I invite you to visit our web site at www.belgradelakes.org. We have a lot of good information on watersheds posted there.