By Jim Banghart Thorndike Pond water sampler
If you visit the NH Department of Department of Environmental Services (DES) website you may come across the Watershed Report Cards and more specially a grade for Thorndike Pond. The reporting and criteria and slightly different than the water quality reports we get from the Limnologist’s office so some of our members may be surprised by the results, as I was. I have reviewed the report card procedure and discussed it with its authors. I will try and explain the differences herein.
The US Clean Water Act requires water quality reports every two years. The report cards are available at the NH DES One Stop site under Surface Quality Report Cards or at http://www2.des.nh.gov/SWQA . Thorndike Pond can be found by first citing the town of Jaffrey (or Dublin) and then pulling up the Stanley Brook report. Stanley Brook is the name of the brook that our lake feeds, starting at the dam and continuing past Stonewall Farm. The assessment units cover a 34 square mile area but is subdivided into more specific units which include Thorndike Pond. There are over 5,000 such assessment units reported by the state.
The 2008 report shows Thorndike Pond as good for swimming and boating but poor for aquatic life and fish consumption. The poor rating for aquatic life is the result of low pH, meaning the water is acidic. Both reports use the same water samples we take each summer which last year showed pH readings between 6.06-6.35 at the deep spot and between 5.96-6.02 on the surface. The Limnologist’s report rates our pH to be acceptable and the Water Quality Report Card rates the same level as poor. The Report Card’s rating is worse for two reasons:
1. The Limnologist averages the readings to get an overall assessment of the lake but the Water Quality Office uses the worst case readings, taking the more strict position that the water should be usable at all times and at all locations around the lake.
2. The Limnologist uses a range of 6.0 to 9.0 as acceptable because that PH supports fish life. The Water Quality Office uses a tighter range of 6.5 to 8.0 because the more extreme values can be harmful to fish eggs and are more problematic for young fish.
The acidity is attributed to atmospheric deposition and is expected to improve slowly over time because of steps taken to improve the broader environment. There is not a problem our members have caused, there is nothing we can easily do, and this situation is common to many NH lakes.
The poor rating for fish consumption is attributed of Mercury levels measured in fish. Our score is based on a state wide alert, there have has been no measurements taken in Thorndike Pond. Again this problem is attributed to atmospheric deposition and the reading is applied across all NH lakes. The Mercury issue is supported by an environmental fact sheet, accessible at the DES website, which suggested limiting fish consumption for fish caught in water bodies throughout the state.
This study is intended to meet the Federal Government’s requirement, as part of the Clean Water Act, for all waters in the state to be coded into 1 of 7 categories:
• 1=Meets standards for all uses
• 2=Some but not all uses meet standards
• 3=Insufficient information
• 4=Does not meet standards
o 4A=has approved remediation plan (total maximum daily load)
o 4B=impaired but doesn’t need a plan
o 4C=impaired but not by a pollutant (low flow or exotic weeds)
• 5=Does not meet standards and there is no plan
On this scale Thorndike Pond would be classified at level 2. There are no lakes in NH rated as level 1. The state DES has their own categorization which maps to the federal codes and they also develop a color coded report card from their categorization. You will see these codes used in the state reporting.
Water is rated for the following uses:
• Aquatic life
• Fish consumption
• Shellfish consumption
• Drinkable water (after treatment)
• Primary contact (swimming)
• Secondary contact (boating)
Because of the treatment allowed for drinking the state rates all lakes as good in that use, so be cautious when looking at those scores.