Winter’s Impact on Water Quality: De-icers and Sand

US-NH-Lake-Wentworth-view-in-winter-snow-bare-trees-JPIt is important to remember that streams continue to flow, ponds and lakes continue to ‘live’ under their ice and our responsibility to maintain healthy water ecosystems continues throughout the winter.

During significant snow and ice storms, road safety requires the application of salts to melt ice and provide safe traction. Each winter local road departments, commercial parking lot owners, home contractors and homeowners use salt to melt snow and ice and to maintain road and other surfaces. As the snow melts or when it rains or snows, salt eventually makes its way to nearby rivers and streams through run off. These chemical de-icers, salt and sand can change the composition of the water and can harm resident insects, fish, and wildlife.

Even when applied in relatively small quantities, salt can:
• Deplete the oxygen supply needed by aquatic animals and plants
• Leach into the ground and change the soil composition, affecting the growth of plants
• Leach into the groundwater and flow into surface water contaminating sources of drinking water
• Deteriorate paved surfaces, buildings, and infrastructures

imgres Sand, which is carried away in runoff, can have the following effects:
• Bury the aquatic floor life, fill in habitats, and cloud the water
• Erode the stream banks and other landscapes as it is carried to the surface waters by stormwater runoff
• Carry phosphorus which acts as an aquatic fertilizer, causing algae blooms and increased vegetation
• Fill catch basins, stormwater devises and storm drains, affecting their effectiveness if not cleaned
• Contribute to plugged storm drains, which can cause flooding

What can you do? Once the snow falls and the lakes freeze:
Cover Up: Cover stored de-icing chemicals and road salt.
Reduce: Instead of spreading de-icers, shovel.
Use alternatives: Non-toxic de-icing substances such as biodegradable cat litter, sand or fireplace ash don’t necessarily melt snow but they do improve traction.
Go for the center: Apply de-icer only down the center of your driveway or walkway. As it melts it will flow to the sides.
Less is enough: Use de-icer sparingly because more does not mean more melting. Be patient: it takes time for de-icers to work. Applying more will lead to unnecessary contamination.
Wait for warmer temperatures: Most de-icers don’t work when the temperature is below 15 degrees. Before granular de-icers melt snow and ice, they must dissolve to form a brine solution. If the air temperature or the temperature of the pavement is below freezing, water may not be available to dissolve the granular de-icer. If you can’t wait, use a liquid de-icer or a pre-wetted de-icer, or focus on sand for traction.
Sweep: Clean up extra salt. If salt or sand is visible on dry pavement, it is no longer doing any work and will be washed away. The excess can be swept up and reused for the next snow or disposed of in the trash.
Drive for winter conditions: The slower you drive, the more salt will stay on the road where it’s needed. And don’t forget — be courteous to slow-moving plows.
We all need to remember, anything we put on exposed manmade surfaces and our land ends up in the water. That’s the way our ecosystem works. Do your part to keep our waters clean in the winter.

Sources: University of New Hampshire Cooperative Extension, University of Maryland Extension, University of Michigan Cooperative Extension

The Freezing of Lakes

Since early August when New Hampshire’s lakes typically achieve their warmest temperatures, our lakes have been cooling off and starting the freezing process. Here’s how it happens…

As the air temperature drops during late-summer, the temperature of the upper layer of the lake drops too. The cooling surface water becomes heavier and denser—eventually to the point that it sinks toward the lake bottom and forces warmer, less dense water to the surface. The process of the upper layer cooling and sinking occurs until the temperature of all the water in the lake drops to approximately 39 degrees Fahrenheit—the point at which water reaches its maximum density.

At some point in November or December, as the air temperature and the water at the lake surface becomes cooler than 39 degrees Fahrenheit, something rather unique happens—the water molecules at the surface spread apart and the water becomes less dense. (Typically in nature as things get colder they contract not expand.) This expansion allows the cooler surface water to float upon the slightly warmer (and more dense) water just below it.

Once the surface water cools to approximately 32 degrees Fahrenheit, its molecules crystallize into interlocking lattice-like patterns and ice is formed. The ice takes up more room than the water it was made from which makes the ice lighter (and less dense) than the water below it—this allows the ice to float on top of the water. If the ice was more dense than liquid water, then it would sink and lakes would freeze completely from the bottom up. Since most aquatic organisms can’t survive being completely frozen, this would cause big problems in lake ecosystems!

Shallower lakes usually freeze before deeper lakes since shallower lakes contain less water that needs to be cooled down. And, lakes freeze from their perimeter towards the center since there is less water in the shallower areas that needs to be cooled.

How does the ice become thicker?

Once an ice film has formed on the surface of the lake and the air above the ice continues to be colder than the ice, the ice will thicken. The cold air above the ice causes heat to leave the lake water under the ice and from the ice itself. This causes the water below the ice to freeze into successively deeper layers. As the winter gets colder and colder, the ice gets thicker and thicker until we can stand—and sometimes even drive—on it without falling through.

Why don’t lakes freeze completely?

At some point, the ice layer itself on a lake will act as an insulator, preventing the cold air above the ice to remove heat from the unfrozen water below. This is why lakes don’t typically freeze completely from top to bottom. The ultimate thickness of the ice layer depends on many variables including the size and shape of the lake, the air temperature, and the duration of the cold air above the ice. In some cases, very shallow lakes or lakes on mountain tops may freeze completely, but this is not often the case in New Hampshire. 

What is the impact of lakes freezing?

The impacts of ice cover are ecologically significant for lakes and their aquatic species. Ice cover regulates lake temperatures, dissolved oxygen levels, light penetration, and many other ecological parameters that govern growth and reproduction of species and interspecies relationships. Because ice cover reduces wintertime evaporation, it helps to maintain a lake’s water level. A lack of ice cover means that winter winds can make contact with lake waters, disturbing fish nesting sites, and impacting the ways lakes stratify, or form layers of water ordered along a temperature gradient. No ice cover also means no snow cover, allowing sunlight to penetrate the water and increase its temperature. In turn, warmer water temperatures may make the lakes more hospitable to non-native species.

Stay Safe!

Have a safe and enjoyable experience on our lakes this winter! No matter what winter activity you enjoy most out on the lake, we hope that you have a safe and enjoyable experience. If you go out onto a lake that appears to be frozen, it is extremely important that you follow basic ice-safety guidelines. For a copy of the “Safety on Ice” brochure, visit the New Hampshire Fish and Game Department’s website at:

or call the Public Affairs Division at (603) 271- 3211.

Reprinted with permission from the NH Lakes Association. 

Where is even more care needed?

shoreline buffer  If you live on shoreline property, maintaining and designing your septic system requires more care than a system located elsewhere. Water pollution can happen even though your system appears to be working well and complies with local health department codes.  Indicator dye put into your septic tank  can help to find problems that may otherwise be difficult to notice.

It’s important to remember, most wastewater treatment happens in the soil below the drainfield in a traditional system. Septic systems on shoreline property are often close to both groundwater and surface waters, and drainfields are sometimes saturated during high water periods. In this case, partially treated wastewater can easily enter adjacent lakes, ponds and streams. Also, as shorelines erode, the distance between the septic system and the shoreline decreases.

Soil and water conditions near the shoreline, including thin or rocky soils, clay soils, and high water tables, may make a traditional septic system less efficient at treating wastes. In these situations, the system may need to be customized to the specific site and may require more advanced treatment technology.

What you can do:

  • Conserve water and spreading the wastewater load over time. This can be especially important at shoreline properties.
  • Pump your tank regularly. Depending upon the size of the system and its usage the system may require yearly or bi-yearly pumping rather than the three year cycle most often recommended.
  • Clearly label any hazardous materials on the premises and do not dump them down your drain.
  • Add appropriate plants between your drainfield and the shoreline. This involves planting areas of small shrubs and trees to help intercept and absorb some of the nutrients before they reach the shoreline. Roots may also stabilize the shoreline and reduce erosion which can contaminate the stream and decrease the distance from shoreline to septic system.  Make sure roots of the plants will not damage the drainfield.
  • Consider a waterless toilet. Incinerator or composting toilets greatly reduce the volume of wastewater that must be treated. Talk to your town’s health department about waste disposal options and permits.
  • Replace or upgrade your septic system. Consider an “alternative” or “advanced” treatment system.

What are they talking about?


Both Lake Wentworth and Crescent Lake are categorized as ‘oligo’ lakes. What the heck does this mean?

First “oligo’ is short for Oligotrophic. If you separate the two parts of this word you have “oligo” which means very little; and “trophic” the root of which is ‘trophy’ meaning nutrients. So an oligotrophic lake is one that has relatively little available nutrients. The nutrients they are primarily referring to are phosphorous and nitrogen.

Scientists classify lake types so they can be easily referred to and their basic characteristics conveyed. In this case scientists are characterizing the fertility of the water body = it’s trophic state.

All lake users and watershed residents (seasonal or year round) need to do their part to keep these lakes in their present oligotrophic states.

Native Plant Growth-Just Something to Get Used To

Aquatic plants are a common sight in New Hampshire’s waterbodies, and many lake residents, as well as visitors to New Hampshire’s numerous waterbodies, may question the importance and role of aquatic vegetation.

Each waterbody may vary in terms of the number, type and distribution of aquatic plants it supports. Over long periods of time, both diversity and distribution of those species can be expected to expand just a little bit, as the lake ages and more organic material accumulates on the lake bottom, making for ideal plant habitat. Sometimes, on a shorter scale, one native plant species or another may become very abundant for a growing season, and then it is present in very low density the next year. Much like we see with acorn production or pine cone production from trees on land, native aquatic plants have “boom and bust” cycles as well.

Usually those booms subside after just a season or two, and the native plants don’t sustain high levels of production for long duration. Bladderworts, native waterweed, water naiad and some pondweeds exhibit this boom and bust cycle. The summer of 2015 happens to be a good year for bladderwort growth statewide, and lots of lakes are seeing floating masses of bladderwort floating around like tumbleweeds.

bladderwort In 2014, it was water naiad that was the abundant species statewide, and in 2013 it seemed like pondweeds were taking off. Each of these have returned to their “normal” levels in waterbodies, and have not continually increased.

Native aquatic plants are not a bad thing in lakes, even though from our own human perspective they can sometimes be a nuisance. Aquatic plants provide many of the same functions as terrestrial plants.

Bladderwort at Walker Pond in Boscawen

Aquatic plants provide a food source, fish habitat, remove carbon dioxide, and produce oxygen through photosynthesis. Plants act as the producers in an ecosystem since they produce their own food as well as food for the consumers or animals of that ecosystem. Aquatic vegetation provides food for tiny microscopic animals called zooplankton, fish, waterfowl, moose and other mammals, and in some cases humans.

Not all aquatic plants are nuisances which require removal. According to DES Wetlands staff, the removal of native aquatic vegetation from lakes and ponds is not allowed. The water, and the land underneath it, is state property and as such, the property owner does not have the legal right to make alterations to that land without a permit.

Removal of native vegetation is considered to be habitat destruction. It should also be noted that the removal of native vegetation inevitably makes room for invasive vegetation to establish itself, further exacerbating a problem the state is already facing. A permit would be required for any type of dredging and removing of sediment and/or vegetation and it’s not likely that such a permit would be granted for an individual property owner who simply wishes to have a swimming area on their waterfront that is free of vegetation.

For questions about native plant management, please contact the DES Wetlands Bureau at 603-271-2147.

Reprinted with permission from auther: Amy Smagula, NHDES Exotic Species Program Coordinator