Conway Lake Sunrise - photo courtesy of Mark Guerringue
Conway Lakes Conservation Association
2022 Annual Meeting
Mark Your Calendars
Date: Saturday August 6
127 Baird Hill Rd.
NHDES reminds boaters to check for invasive species
Concord, NH – The New Hampshire Department of Environmental Services (NHDES) wants to remind anglers and boaters to make sure to clean, drain and dry your boats and trailers and disinfect your fishing and other aquatic recreational gear. All of the Northeast states (Connecticut, Maine, Massachusetts, New Hampshire, New York, Vermont and Rhode Island) will thank you if you do. Millions of dollars are spent each year protecting the ponds, lakes, rivers and streams that call to you when the spring peepers are singing, and the snowdrops are blooming. Together we can keep your favorite fishing hole or aquatic getaway an invasive-species-free, enjoyable and relaxing place to be.
“New Hampshire’s lakes and rivers are a big draw to our region. Aquatic recreational activities abound, but so do aquatic invasive species,” says Amy Smagula, NHDES Exotic Species Program Coordinator. “We count on boaters to self-inspect their gear and clean, drain and dry when they are in New Hampshire, and in other states in the region because we are all connected.”
Also, remember that if you are boating in New Hampshire or in Maine with vessels registered in a different state, you must purchase a state-specific, out-of-state boater decal to boat on waters in those states. The New Hampshire decal is $20 and can be purchased online and the Maine Lake and River Protection sticker is $45 for non-resident boaters and can be purchased on the Maine Inland Fisheries and Wildlife website.
2021 Invasive Species Patrol Report
The Aquatic Invasive Species (AIS) Patrol is a group of CLCA volunteers who survey the lake’s 21 miles of shoreline in canoes, kayaks, on paddle boards, or while swimming/snorkeling, checking for the appearance of invasive plants and animals. Early detection is critical -- once introduced, they grow vigorously and spread rapidly.
Our goal is to collectively patrol the entire shoreline of Conway Lake twice a month for the duration of the growing season, usually July through September. We’ve divided the shoreline into grids so that we can track those areas that been patrolled and to communicate the location of interesting or suspicious plants or animals. The map to the left shows the grids that were surveyed at least once during the 2021 season (shaded green). The grids that were missed are shown in yellow. We endeavor to cover all areas of the lake shoreline at least once a month and many of the key areas were surveyed multiple times over the course of the season. Thanks to all of our volunteers who did such a great job in covering the lake!
Fortunately, we can report that no invasive animal or plant species were found in the lake in 2021. We keep adding to our knowledge base of native plants and animals in the lake and this year our volunteers added two additional plant species to our list of known native species in the lake.
Invasive species are primarily introduced to a lake by "hitching" a ride on boats and recreational gear and can appear anytime. If left alone invasive species will grow vigorously and spread rapidly clogging shallow water areas and damaging boat engines, and docks. Early detection is critical -- once introduced, they grow vigorously and spread rapidly. It is difficult and costly to control or eradicate most of these species once established so successful remediation of a new infestation is dependent on early detection and action.
Our volunteers are the "eyes" of Conway Lake, and their efforts are essential in preserving Conway Lake as we all love it. Please consider joining our group of volunteers, even if you are only available for part of the summer. It’s a great way to enjoy Conway Lake and you can feel good about playing an important role in keeping the lake healthy.
Map showing locations surveyed by the AIS Patrol
Fall 2021 Update
This past Fall, Bill Petry, Maria Gross, and Don Yurewicz systematically collected water samples from 15 streams that feed into Conway Lake. The table to the left shows the phosphorous levels of the streams we sampled. The samples were analyzed on an expedited basis by Bob Craycraft's lab at UNH. We had requested the analysis be conducted as soon as possible as we were concerned with the increases in the Fall 2020 results. Bob was very responsive to our request and provided his assessment of the results which were reassuring. Bob stated that the absolute levels were consistent with other healthy lakes in the area.
As can be seen in the table the average amount of phosphorous in all 14 streams decreased 15% from Fall 2020 to Fall 2021 collections. This variation has many elements, and recent precipitation is suspected to be a driver. We attempt to collect our samples soon after a rain event, but warm or wet seasons have an uncontrollable major impact.
Phosphorus is usually considered the “limiting nutrient” in aquatic ecosystems, meaning that the available quantity of this nutrient controls the growth rate of algae and aquatic plants. In excess, however, phosphorus can lead to excessive algal and cyanobacteria growth (blooms) which may contain dangerous levels of toxins. Since phosphorus generally occurs in small quantities in the natural environment, even small increases can negatively affect water quality and biological conditions. At the current levels found in Conway Lake, phosphorous is in balance and does not cause problems. Excessive phosphorus is often caused by human activity including use of lawn fertilizer and failed septic systems that can leach into the lake. These can be accelerated by storm runoff, both from lakefront properties and from sources elsewhere within the watershed.
We must all remember that what happens on our property affects the lake - to this end please prevent runoff into the lake, curtail the use of fertilizers, and be sure your septic system is operating correctly.
Remapping Conway Lake Bathymetry (Water Depth)
A project was initiated in July 2021 to remap water depth across Conway Lake. The current map available from the NH DES greatly oversimplifies lake floor topography and overextends the area of shallow water. This impacts the areas that need to be patrolled for aquatic invasive plants in the lake. A portable sonar device that records water depth and latitude/longitude and a sounding line were used to collect raw data. Over the course of last summer, 70 transects were made across the lake that collected over 100K sonar data points. The data were then downloaded into GIS mapping software to create a new depth map. Large rocks and boulders were also mapped based on Google satellite images of the lake. Additional data will be collected in 2022, but in the meantime, an interim map is available on the CLCA website – see the Maps folder on the Resources webpage.
So, what does the new map show? For one it depicts a much more accurate limit to the shallow water littoral zone (depths less than 15') where aquatic plants can grow and where the AIS patrol needs to patrol for possible invasive plants. The mapped area of aquatic plant growth has decreased by roughly 50%. Reducing the area of shallow water has in turn increased the total volume of the lake by approximately 30%.
Sonar profiles and depth data show that the axis of the lake is characterized by a gently sloping and smooth bottom – probably the result of glacial scouring, whereas the margins of the lake are marked by numerous submerged knolls, some of which break the surface, or are shallow enough to be boating hazards. Most of these were not shown on the old map. These knolls are probably erosional bedrock highs capped with glacial till left by retreating glaciers. Lake margins vary from gentle slopes (e.g., the north end of the lake), to steep cliff-like escarpments, to terraced step-down margins. The deepest measured point in the lake is still 49’ and sits directly east of Andrews Point. There is a spot nearly as deep (48’) ENE of Ship Island.
Click here for a more detailed description of the project and summary of findings. For questions about this project please contact Don Yurewicz (firstname.lastname@example.org).