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Lake Water Quality Monitoring

What is the SLA's Water Quality Monitoring Program (WQMP)? 

The SLA has had an active water quality monitoring program for over three decades.  The Water Quality Monitoring team, in conjunction with NH DES' Volunteer Lake Assessment Program (VLAP), collects water samples between May and September to measure the chemical, physical and bacteriological characteristics of the Lake.   Samples are sent to DES's limnology labs for analysis and form the basis of their Annual Reports. The latest VLAP is available in the sidebar.  

Where samples are taken and is what being measured? 

In 2022, working with the Town's Watershed Committee, the WQMP was greatly expanded to gather an even more detailed picture of the Lake's physical and chemical profile.  Water samples were be taken at 31 locations (versus the typical 25) both in the watershed and at shoreline:  the deep spot11 inlets  (where ‘streams’ flow into the Lake), 7 beaches, the boat ramp, and the outlet/dam.  Importantly, several up-stream locations were added in 2022. 

Fourteen water quality parameters are to be sampled during each sampling event. These are: Dissolved Oxygen and Water Temperature by meter, Color, Chloride, E. coli bacteria, Acid Neutralizing Capacity, pH, Alkalinity, Total phosphorous, Water clarity (via Secchi disk), Conductivity, and Turbidity, Total Nitrogen, Organic Carbon, and Phytoplankton.  

What are the 2022 WQMP Results & Trends?

To help understand the science, use our Glossary of Lake Terms.

The Not So Good News
  • High, and increasing levels, of Total Phosphorus (TP)
  • Low and decreasing levels of Dissolved Oxygen (DO) at the deeper spots
  • Chloride levels are increasing, but still significantly below "Chronic" level. 

There is some Good News

  • No significant levels of E. coli were detected at any of the beaches or the boat ramp.
  • Good to excellent results for most water quality parameters.
  • 2021 VLAP Report characterized Spofford Lake water as having "high quality conditions."
Other Findings:
  • Locations of concern for the tributaries were similar to prior years: high E. coli and/or Total Phosphorous for one or more sampling events at the Clarkdale Pipe and Watershed, Route 63-3, Moose Hollow Inlet and Moose Hollow Watershed, LaChance Inlet and LaChance Inlet Watershed, and Camp Spofford Inlet and Camp Spofford Watershed.  Moderately high Total Phosphorus levels were also detected at the Outlet for two of the sampling events.
  • Conductivity levels (i.e., salt) were consistently high for almost every tributary and watershed sample.
  • Moderately high pH levels were detected at one or more sampling events at seven of the stations.
  • At the Deep Spot, most sampling results demonstrated good or generally good water quality for most parameters:  color, chloride, chlorophyll-A, acid neutralizing capacity, clarity, and color.  
However, conductivity was excessive for every sampling event.   Additionally, high or excessive levels of TP and low levels (< 5mg/L) of DO were detected at the deeper areas.  

New Inlet vs. Watershed Sampling Program:

  • In 2022, for the first time, the WQMP established new sampling stations at Ware's Grove, Camp Spofford, Seaman’s Inlet, Route 63-3, LaChance Inlet, Moose Hollow, and the Clarkdale Pipe  
  • Due to drought conditions, this initiative provided less data than expected. Nonetheless, the data collected provides some indication of the primary source of contaminants, either from watershed or at the shoreline.
  • Due to the paucity and quality of the data collected, no firm conclusions can be drawn.  The SLA and Town's Watershed Committee have agreed to continue this program through at least the 2023 sampling season. 

New Winter Chloride and Conductivity Sampling:

  • On January 26, February 24, and March 30, samples were collected for chloride and conductivity at six tributary locations between Ware's Grove and Silverdale.
  • Of the 17 samples collected (one tributary was frozen during the January sampling event) for Chloride a total of four samples (23.5%) involving three sampling stations (Boat Launch, Route 63-3 and Seaman’s Inlet) exceeded the VLAP criterion of 230 mg/L for classification as “chronic.” 
  • Of the 17 Conductivity samples tested, 13 samples, involving five of the six stations, exceeded 100 µMhos/cm, which indicates “human disturbance.”
  • Winter Chloride and Conductivity sampling detected higher than desirable levels of Chloride and Conductivity on several occasions.  The levels did not vary significantly from, and were often lower than, the levels detected during the 2021 summer season. 

New Sampling of Total Phosphorous (TP) During Turnover:

  • With assistance from DES, TP was sampled during spring (April 6) and fall (November 23) during turnover conditions. 
  • DES noted that the TP data collected in October, at the mid and lower depths, suggested that  internal loading of TP is occurring, and that late season sampling be continued.
  • The DO and TP data collected over the course of the summer sampling program appears to indicate a strong correlation between decreasing DO levels and increasing TP concentrations at the deep spot, which is likely attributable to internal loading.
Rising phosphorus levels accelerate plant growth; think more plant growth and decay, algae, and cyanobacteria.  Low dissolved oxygen indicates, and further amplifies, phosphorus and  harms some aquatic species.

What about the 2023 WQMP?

The 2023 program will replicate the 2022 program in hopes of gaining more data and possibly capturing results from stations where weather disallowed the appropriate sampling in 2022. 

 What can I as a homeowner do to help?

Take time to understand the Lake's vulnerabilities and take steps to maintain and improve Spofford Lake's water quality.  Be aware that the SLA-funded Watershed Management Plan and the SLA-funded Core Sediment Analysis provide greater context to the VLAP reports.  

Implement practices to minimize runoff from your property, for example:

•  make sure that you have a well functioning septic systems and that they are pumped out regularly   

     refrain from adding sand to beaches, as this only encourages plant growth and resulting decay

  • reduce or eliminate winter salt on driveways and walkways
  • use a salt alternative in your water softening system.  Salt used to soften water eventually flows into Lake.   'Sodium Shield' is available at the Brattleboro Agway

     use “lake friendly” cleaning and lawn products.  Products labelled 'Safer Choice,' an EPA initiate, are a good choice.  

  • participate in LakeSmart, a free program to identify how your property can become more lake-friendly. 

Page updated August 18, 2023

Spofford Lake Association

PO Box 177
Spofford, NH 03462

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