A FLOATING ICY COVER
The process of lakes turning over in the fall is critically important to the frogs, turtles and fish living in the lakes. It is during this turnover period that oxygen is infused and distributed throughout the entire water column. So how does this occur? As summer transitions to fall, the surface of the water eventually cools to 39.2 degrees Fahrenheit. This cool water settles to the bottom of the lake and pushes warmer water to the surface. Eventually, all of the lake water cools to this “magic temperature” and the lake is then ready to freeze. This natural cooling process is called fall overturn.
When water freezes, it floats. This icy cover is important for the life cycles of most aquatic organisms. Ice cover controls UV light exposure, oxygen levels and nutrients in our lakes. Warmer water holds less dissolved oxygen than cooler water and fish survive and reproduce in waters of specific temperatures and oxygen levels. In winter most fish spend their time near the bottom of the lakes, where the food and warmest (39.2°F) water lies. Upper Lake and Alpine Pool ice over earlier in the winter than Lake Mohawk because there is less water to
cool. Most lakes and ponds don’t completely freeze to the bottom because the ice (and eventually snow) on the surface acts to insulate the water below.
Structures such as boat docks and bulkheads retain heat and warm up the immediate area, increasing the time it takes water to freeze. Structures speed up the thawing process as well. Bubbling machines also prevent ice from forming. It is important to the ecosystem of our lake for ice to form and maintain a cover in the winter. And don’t forget ice allows the enjoyment of many winter sports in Lake Mohawk! Without an icy cover, algae may bloom more and earlier in the spring and our water creatures may not survive. Consider what you can do to maintain
this protective cover.
ROAD SALT CONTAMINANTS
In addition to plowing and shoveling, keeping Lake Mohawk’s roads and walkways passable involves the use of road salt. Sodium chloride (NaCl) is the primary deicing chemical used and is popular because it is available, relatively cheap and very effective. The reason it works for deicing is because it lowers the freezing point of water. Calcium and magnesium chloride preparations may be used by homeowners, but are more expensive options to NaCl.
Actually, the road salt that is spread on our roads is a 50% / 50% mix of salt and sand and is applied in order to use the minimum amount of deicing material. This practice helps reduce the potential for grit, sand, and salt to enter Lake Mohawk’s water bodies and supports a goal of the Foundation. In the spring, and sometimes in winter, road sweepers will be activated to sweep the grit off roads- further reducing the potential for material to enter our water.
Increasing use of salt can be detrimental to our environment. Salt spray from roads accumulates on roadside plants and vegetation causing “leaf burn.” This damage from dehydration and nutrient imbalance is readily visible around the Reservation. Contaminates from road salt also enter our water bodies through runoff and storm drains, possibly affecting the water quality of our lakes and impacting the crustaceans, salamanders, frogs, fish and plants living in the water. The accumulation of chloride (from NaCl) can impede lake turnover and mixing, depriving the bottom layer of the water body of oxygen and making it difficult to support aquatic life.
We are seeing more trucks on New Jersey roads that will wet the salt and apply it to roads prior to snow storms. The dissolved salt begins working sooner and results in faster deicing. In New Hampshire, the Department of Environmental Services found that pre-wetting road salt reduced salt application by 20 percent. This pre-wetted salt adheres to the pavement better than solid salt, reducing the amount of salt bouncing off the roads
Salt in our water is difficult to treat after the fact, so a reduction in the amount of salt homeowners use is the most effective management strategy. Removing snow before it ices is helpful in reducing slippery walkways. Adding sand or gravel to your salt can help with traction. Consider the impact on our lakes and environment as you use chemicals within the Lake Mohawk Reservation.