How the NLWA is working to protect Northwood Lake and its watershed
Milfoil Control Diving Program
Variable milfoil is an invasive aquatic plant. The infestation of milfoil in our lakes and ponds is one of the biggest threats to our waters and could cost millions of dollars in reduced property taxes, removal expenses and lost tourism dollars. Heavy plant growth causes entanglement of boats and motors in thick weed beds, causes problems for fishermen, and represents a nuisance and potential danger to swimmers. The plants break apart easily due to wave action caused by boaters, swimmers, fishermen and wildlife. These fragments drift to new areas of the waterbody, where they settle to the bottom and root. Left untreated, the plants will take over and will grow upwards and spread across the surface of the water. The NLWA contracts annually with a professional dive company to perform Diver Assisted Suction Harvesting (or DASH) in both sporadic growth and dense growth areas. When suction harvesting, a diver hand pulls the targeted plants, being careful to remove the entire root system and to minimize fragmentation. The plant is placed into a suction hose that takes it to the surface. Once at the surface, the plant is discharged into a perforated discharge vessel where the filtered water and sediment is allowed to flow back into the lake. The plants are left behind and are raked into tubs that are stacked for transport and removal. The plants are not chewed up in the suction process because the pumps are set up on a jet loop venturi system. This allows us to bypass the pump and discharge the plants intact, greatly reducing fragmentation. This also allows any marine life that should get caught in the suction hose to be returned to the water unharmed. Some people confuse suction harvesting with dredging. We are not dredging the lake bottom, but simply hand pulling the target plants and using suction to get them to the surface. The objective is not to remove the sediment but to remove only the target plants. What little sediment is removed with the root system of the target plants is discharged back to the lake bottom. This helps us to minimize the amount of sediment suspended in the water column and allows us to maintain maximum visibility in order to keep the divers working for as long as possible on each site.
Lake Host Program
Since its inception in 2002, the objective of the Lake Host program has been to place trained Lake Hosts, both paid and volunteer, at public boat launches in order to educate visiting boaters about exotic plants by distributing brochures, answering questions, and completing a brief boater survey. Lake Hosts conduct courtesy boat and trailer inspections of vessels both entering and leaving public waters, and show boaters where to look for hitch-hiking plant fragments on boats and trailers. Boaters are encouraged and to conduct self-inspections. Any plant material found is removed and properly disposed of and the samples of suspicious plants removed from vessels are bagged and sent to the New Hampshire Department of Environmental Services (NHDES) for identification. If you are interested in becoming a part of the Lake Host Program on Northwood Lake, please contact the NLWA.
Water Quality Testing
Water quality samples have been collected on Northwood Lake since 1991 by volunteers through the Volunteer Lake Assessment Program (VLAP) and analyzed at the NH Department of Environmental Services (DES). In the spring of 2008, the Directors of the NLWA decided to perform independent testing in order to increase both the frequency of sampling and the number of sampling sites around the lake.
Escherichia coli, better known as E.coli, is the most common species of fecal coliform bacteria associated with humans and other warm-blooded animals. Common causes of high E.coli counts are agricultural runoff, waterfowl feces and faulty septic systems. Obvious things we can do to prevent E. coli contamination are to have our septic systems pumped and inspected for leaks regularly. Avoid feeding waterfowl of any kind and make sure that if you allow animals near the water's edge, their feces is not allowed to enter the lake.
Another common pollution indicator test is total phosphorus. Phosphorus sources within a lake's watershed include septic system failure, animal waste, lawn fertilizer, eroding roadways and construction sites and storm water runoff. Several sampling sites on Northwood Lake have produced persistently high phosphorus counts. There are a number of things we as landowners on the lake can do to help reduce high phosphorus levels. Use phosphate-free laundry detergent and dishwashing detergent. Use organic, slow-release fertilizer on lawns. Avoid bathing yourself or pets in the lake. Prevent erosion and runoff on your lakefront property by planting native vegetation along and near the shoreline and eliminate large grassy lawns. We can beautify our properties while simultaneously contributing to the overall health of the watershed by providing these buffers between storm water runoff and the lake.
If you have a water quality concern in your area, or you would like to become a part of our water quality testing program, please contact the NLWA.
Cyanobacteria
A few New Hampshire lakes (including Northwood Lake) have been found to contain a unique cyanobacteria taxa called Gloeotrichia. Each colony of Gloeotrichia may contain approximately 5,000 cells. The colonies look like very small, fuzzy balls in the water. They can appear either green or sometimes brownish-yellow by eye. Oftentimes, these cyanobacteria do not accumulate to large concentrations and may go unnoticed. These types of cyanobacteria do not typically form green surface scums, however they can quickly accumulate along shorelines and coves. The water may appear cloudy in areas of higher concentrations.
Surface blooms can rapidly change and accumulate in various locations around a waterbody. Please continue to monitor your individual shorelines for changing conditions and avoid contact with cyanobacteria bloom accumulations.
Cyanobacteria are natural components of water bodies worldwide, though blooms and surface scums may form when excess nutrients are available to the water. Some cyanobacteria produce toxins that are stored within the cells and released upon cell death. Toxins can cause both acute and chronic health effects that range in severity. Acute health effects include irritation of skin and mucous membranes, tingling, numbness, nausea, vomiting, seizures and diarrhea. Chronic effects may include liver and central nervous system damage. Be cautious of lake water that has a surface scum, changes colors, appears cloudy or has green streaks or blue-green flecks.
If you notice anything resembling cyanobacteria, please refrain from wading, swimming, or drinking the water. Keep all pets out of the water and contact NHDES immediately. Please call NHDES to report a cyanobacteria bloom at
(603) 848-8094 or email
HAB@des.nh.gov.
