Stocker Pond Water Quality and Testing
To quote from the NH DES article on Lake Eutrophication, "lakes are divided into three trophic categories: oligotrophic, mesotrophic and eutrophic. The prototypic oligotrophic lake is a large deep lake with crystal clear waters and a rocky or sandy shoreline. Both planktonic and rooted plant growth are sparse, and the lake can support a coldwater fishery. A eutrophic lake is typically shallow with a soft and mucky bottom. Rooted plant growth is abundant along the shore and out into the lake, and algal blooms are not unusual. Water clarity is not good and the water often has a tea color. If deep enough to thermally stratify, the bottom waters are devoid of oxygen. Mesotrophic is an intermediate trophic state with characteristics between the other two."
Stocker Pond is currently classified as a mesotrophic body of water.
Pending the 2025 VLAP water results which will arrive in early 2026, we
display some trends updated based up water samples taken by Karin and Ken
Nicoll in June and August, 2025. Click on the thumbnail for the larger image.
Chlorophyll, phosphorus, and transparency are three markers by which
to categorize the trophic level of lakes and ponds. In the table below
(extracted from the
Wikipedia page
on Trophic State Index) we see some standard ranges for these
categories by trophic type. Probably these are national averages.
Transparency is quantified by the maximum depth (meters) at which a
30cm (12 inch) Secchi disk
remains visible.
The next image is a graph containing historical water trends for Stocker
Pond. The data is collected annually by residents (currently Karin and
Ken Nicoll) and the graphical and historical
presentation is produced by the NHDES Volunteer Lake Assessment Program
(VLAP). The graph below is extracted from their
2024 document
for Stocker Pond, but it's a bit dense with information and
abbreviations which deserve some explanation.
The full report contains a great deal more detailed information than is
summarized here. Below are links to recent documents:
2024
2023
2022
2021
2020
2019
The dotted and dashed lines represent BTC Thresholds (Best Trophic
Classification) for Chlorophyll and Phosphorus. The green dotted line
indicating approximately 5 micrograms/L seems roughly in the middle for
mesotrphic values in the previous table, while the red dashed line at 12
micrograms/L is the boundary of oligotrophic and mesotrophic in the
previous table.
For the purposes of interpreting the graphical data, values above the
treshhold are considered poor.
Since approximately 2015, Stocker Pond has been below the thresholds for
both Chlorophyll and Phosphorus, but these data should be viewed with
some reservation since most of these readings are from a single sampling
of the water and all manner of climate conditions can affect these
readings.
Transparency (the blue bars) seems quite variable, generally between 2
and 3 meters since 2015, measured without a viewscope (NVS),though with
view scope (VS), the readings are better (see full document).
Much of the variability may be due to using the data coming from only a
single sample.
VLAP Data Summary from 2024
-
Pond nutrient (phosphorus) levels and algal growth (chlorophyll) have
remained within a higher range since 2022 following a period of
decline.
The increased intensity of storm events and associated stormwater runoff and fluctuating climate conditions resulting in shorter periods of ice cover, warmer water temperatures, and longer periods of thermal stratification can impact pond quality over time. Pond nutrient (phosphorus) levels, algal growth (chlorophyll), water clarity (transparency), and turbidity have improved since 2015. -
Moreover (see the full report), the percentage of
cyanobacteria in the phytoplankton population at 73% is a
dramatic increase over the 40% from 2022, and in general 20% higher
than all readings from the last 10 years.
Once again, this may or may not be attributable to the single water testings we typically perform.
VLAP Recommendations from 2024
- It is suggested to increase monitoring frequency to once per month, typically June, July and August, to better assess seasonal water quality and make comparisons with historical data.
- Stormwater runoff is the leading contributor to nutrient pollution in our surface waters. Identify areas prone to stormwater runoff and erosion and implement best practices to reduce runoff and erosion.
- Encourage shoreline property owners to be certified LakeSmart through NH LAKES lake-friendly living program.
- Continue to encourage local road agents to remove winter sand and salt accumulation along roadside ditches and culvert that discharge to the pond.
- Survey the shoreline and sandy areas for the presence of freshwater mussels and clams and submit samples to NHDES for identification.