Summer 2019 Water Quality Update
CPIA volunteers work directly with the NH Department of Environmental Services (NHDES) collecting samples and monitoring Cobbetts Pond water quality. Cobbetts Pond has experienced declines in water quality in recent years. The Cobbetts Pond waterfront and total watershed has experienced substantial residential, commercial and roadway development. All this development contributes to the total nutrient load into Cobbetts Pond. Chlorides, Total Phosphorus and Chlorophyll-a, continue to trend in the wrong direction and are our biggest concerns. The impact has led to Cobbetts Pond being listed as a threated/impaired body of water by the US EPA and NH DES.
Cobbetts Pond is currently designated with Eutrophic state by the NH Department of Environmental Services. There are 3 classifications, Oligotrophic (best quality), Mesotrophic (medium quality) and Eutrophic (worst quality).
What activities cause Eutrophication? Since eutrophication is increased nutrient input, any activity in the watershed of a lake that increases nutrient input causes eutrophication. Land use changes can result in significant changes in nutrient runoff. Studies in New Hampshire have shown that phosphorus export from agricultural lands is 5 times greater than from forested lands, and urban/residential areas may be more than 10 times greater. Stormwater runoff from these developed land areas is the major source of nutrients for most lakes. Other activities that contribute to eutrophication are lawn and garden fertilizers, faulty septic systems, washing with soap in or near the lake, erosion into the lake, dumping or burning leaves in or near a lake, and feeding ducks.
Have you seen more weed growth and algae blooms?
The main effects of eutrophication are an:
• increase in plant and animal biomass.
• increase in growth of rooted plants, e.g. reeds.
• increase in turbidity (cloudiness) of water. increase in rate of sedimentation.
• development of anoxic conditions (low oxygen levels) decrease in species diversity.
Cobbetts Pond biggest concerns continue to be conductivity/chloride levels and nutrient (phosphorus) levels. The northern end of the lake tends to see more nutrient runoff and has higher phosphorus and chlorophyll levels (with significantly increasing trends). The southern end of the lake fairs a bit better with lower phosphorus, chlorophyll-a, and conductivity/chloride levels. This year, the June sampling event indicated excessive phosphorus levels in Bella Vista stream. The CPIA is working to implement a rain garden in that area to capture some of the runoff and neutralize before it enters the pond.
Following Historical Water Quality Data and Summer of 2019 Data
July 2019 Cobbetts VLAP Water Test Results
20/30 Light tea color
Chloride 107/108 Indicates pollution from road salting and runoff
Chlorophyll-A 5.36/5.46 More than desirable, indicator of Algae concentration
PH (acid/basic) 7.38/7.63 Satisfactory
Secchi 2.8/2.5 Good Water Clarity
Conductivity 381/378 May indicate pollution from road salting and runoff
Turbidity 1.24/0.96 Median for NH Lakes = 1
Total phosphorus 13.4/12.4 Average
You may have heard or seen news this summer concerning Cyanobacteria and hazard to pets and humans. Cyanobacteria are some of the earliest inhabitants of our waters, and naturally occur in all our lakes and ponds, often in relatively low numbers. However, research indicates that Cyanobacteria abundance increases as lake nutrients increase. Cyanobacteria typically reside at the bottom of the lake. However; increased water temperature and light in the spring promote upward movement in the water column toward the surface where blooms or scum may be formed. These blooms contain toxins that adversely affect pets and humans. The CPIA volunteers monitor the waters for potential blooms and if suspected contact the DES for confirmation. If a Cyanobacteria bloom is detected and tested positive, then DES will issue a public notice to the public. The last time Cobbetts Pond experienced a Cyanobacteria bloom was in 2009.
What you can do to help improve Cobbetts Pond water quality?:
• Please support the CPIA by paying annual dues plus any additional donations or volunteer efforts.
• Become a Lake Smart Advocate, Download your free Lake Smart book at https://nhlakes.z2systems.com/np/clients/nhlakes/product.jsp?product=32&
• Build buffer plant zone along the waterfront
• Do NOT fertilize your lawn. GREEN LAWNS mean GREEN LAKES
• Do NOT use salt or other harmful ice reducing agents
• Do not feed ducks or geese and discourage their overall presence.
• Do not use pesticides or herbicides along the waterfront
o Per the NHDES rules, only a licensed professional with a permit can apply herbicides in surface waters or wetlands, or within 50 feet of the reference line of a public water body (like Cobbetts). See the fact sheet here: https://www.des.nh.gov/organization/commissioner/pip/factsheets/sp/documents/sp-5.pdf .
o Other locations outside of that distance from the water are regulated by the Department of Agriculture, so you may want to check with them, if the NHDES fact sheet doesn’t cover your specific circumstance. https://www.agriculture.nh.gov/laws-rules/index.htm
• Utilize rain barrels and build rain gardens on your property to prevent storm water runoff from reaching the lake.
• Remove Asian Clams and Chinese Mystery Snails whenever possible.
• Properly maintain your septic system. We recommend pumping your system at a minimum every 2 years.
• Monitor boats accessing the lake to make sure they are free of Milfoil.
• Immediately pick up after pets.
• Report offenders. http://des.nh.gov/organization/commissioner/pip/report_complaint.htm
Please follow theses guidelines to ensure this wonderful natural resource can be enjoyed for generations to come.
• NHDES VLAP Data
• New Hampshire Lakes Association Lake Smart Book
• Cobbetts Pond Watershed Restoration Plan 2010
• NHDES Fact sheet WD-WMB-10 Cyanobacteria
Copyright © 2019 Cobbetts Pond Improvement Association*, All rights reserved.
The Cobbett’s Pond Improvement Association (CPIA) is a 501(c)(3) non-profit, volunteer based organization whose purpose is to oversee the well-being of Cobbett’s Pond. It is our goal to maintain the health and beauty of Cobbett’s Pond so that all may enjoy it’s beauty for generations to come. Please consider a tax deductible donation today! – Thank you and our water thanks you.
Our mailing address is:
P.O. Box 912 Windham, NH 03087
Since the 1980’s the NH Department of Environmental Services and the Cobbett’s Pond Improvement Association (CPIA) have tested water samples from the pond. Unfortunately, over this time period, test results have shown a significant deterioration of the pond’s water quality.
A major contributor to the decline in water quality is development in the watershed. The watershed is the area that funnels water runoff and other nutrients into the lake. Although it is fact that the water quality isn’t what is used to be, there are steps that residents can take to help improve the situation.
The NH Department of Environmental Services has comprised a list of recommended practices that residents should consider adopting to improve water quality. This information can be found at the following link.
DES – Volunteer Lake Assessment Program annual results and recommendations:
The DES has information on how how to manage stormwater runoff around private residences. This information can be found on there website by following the link below.