BLIMP Water Quality Monitoring Program

Monitoring water quality in addition to invasive weed control is critical to the future of our lake. The complexities of where to sample, how frequently to sample, what parameters to measure, etc, are important considerations in monitoring water quality. In collaboration with the University of New Hampshire, BLIMP is actively monitoring each of these important considerations:

Sampling Sites and Frequency. We are sampling 6 different sites on Balch:  two “deep lake” sites with depths of 46 feet—the deepest part of Balch—and a 42 feet site not too far from Custom House Island; the mouth of the river inlet (near the net) to get a sense of the water quality coming into the lake; the middle of Stump Pond, since a significant amount of the ProcellaCOR chemical application occurs there; near the entrance to Wyman Cove as a nearby site to chemical application, and Stoddard Narrows, where Balch starts to narrow to form the outlet to the dam and thus represents the outflow partner to the river inlet sample. 

If you’re wondering why we use a combination of deep-water and much shallower sampling sites, here’s the rationale:  Shallower sampling sites like the river inlet, Stump Pond, Wyman, and near the dam are “leading indicators” of problems.  Changes in these areas might be very short-term but they give us a heads-up that lake-wide trouble may be ahead.  The two deep-water sites are “lagging indicators”, meaning that if they start to go south we need to take immediate action. Very importantly, the deep-lake data is how the state and other organizations (for example, the Acton-Wakefield Watershed Alliance) classify Balch and directly affects how Balch Lake is presented to folks interested in renting or buying. For these reasons, the primary deep-lake site is considered the most critical and is the one most carefully probed.

For the remainder of this season and the 2022 season, we are planning to do bi-weekly samplings from early May through early October. There is a trade-off between sampling frequency and number of sampling sites. We believe the “sweet spot” for Balch is every other week at 6 sites—more sites than any other comparable lake in the LLM program

Parameters to Measure. Depending on the sampling site, we will be monitoring several different critical parameters. Among the options we have considered include water clarity, chlorophyll, phosphorous, water color, pH, alkalinity, dissolved oxygen, and cyanobacteria.  Here are the parameters we will be measuring and the rationale for doing so:

Water clarity: This is a critical parameter for Balch and most other lakes and ponds because it combines key factors such as water color, algal (typically cyanobacteria) blooms, and siltation. The further down light can penetrate correlates positively with overall lake health, and it also correlates with how deep we might expect to see invasive plants. Since invasive plants require light to grow, this measurement in combination with the experiences of our divers gives us an idea of where potential growth areas might be for us to keep an eye on. Water clarity is measured at the primary deep-lake site of 46 feet.

Phosphorous/Phosphate: This is the most important leading indicator for potential water quality issues on Balch Lake. Phosphates are the major contributor to overall plant and algal growth In Maine and New Hampshire. Fortunately, lakes like Balch do not need to be overly concerned with acid rain, pH, or buffering capacity (also known as alkalinity—more on this later). Phosphates are the limiting factor for algae and water plant reproduction and comes primarily from lawn fertilizers and detergents that can leach into the lake as well as human waste/septic system failure. Because they are such an important parameter to measure, all 6 sampling sites are monitored for phosphates.

Water Color: Water color per se is not a direct indicator of lake health—most lakes including Balch have noticeable color due to dissolved acids (typically tannins, the same acids found in red wine and coffee beans) and nutrients that are part of the lake via rain run-off, endogenous plant degradation, and lake bottom solid constituents that dissolve into the lake. By the way, nearly all “colorless” lakes are actually dead from a biological standpoint due to acid rain conditions combined with a lack of buffering capacity (alkalinity—discussed later). Nonetheless, it’s important to monitor color as it provides useful information when combined with water clarity observations. It is normal for water color to change as the growing season progresses from May to October but it should be reasonably consistent from year to year. More importantly, if water color increases it is a sign that something has changed that we need to figure out. Water color is measured at the primary deep lake site.

Chlorophyll: Since all algae and other plants make chlorophyll, measuring the amount of chlorophyll in a sample gives an excellent indicator of the algal load on Balch along with a general measurement of plant degradation. This will be done at the primary deep-lake site.

Cyanobacteria: Commonly known as blue-green algae, cyanobacteria are the most common cause of algal blooms in Maine and New Hampshire lakes. These blooms result in large fish kills and a loss of swimming and other recreational opportunities when they occur. Cyanobacteria produce a specific chemical than can be readily measured. We will be taking water samples for cyanobacteria at the deep-lake site and any other sites where an algal bloom is sighted or reported.

pH and Alkalinity: These two parameters are closely related. pH is the measurement of how far from neutral (pH 7.0) the lake water is. Ideal pH values are between 6.8-7.4, and an acid-rain affected lake is likely to have a pH of less than 6.6. The last measurements in July 2020 and July 2021 were 7.1 and 7.0. The last measurement before 2020 was in 2003 and was 6.9, which is in good agreement with the past two years.

The “buffering capacity” of a lake is measured by alkalinity, ie, how sensitive the lake is to acid rain, acidic water run-off, etc. A drop in alkalinity can be an early indicator of problems and is important to detect early-on.

Because lakes like Balch do not have a history of acid rain, pH, or alkalinity issues, we do not plan to monitor these parameters at the present time and will evaluate this decision on a year-by-year basis.

Dissolved Oxygen: Dissolved oxygen is an important parameter for lakes that support cold-water fisheries such as trout and land-locked salmon. It is also important for shallower lakes that struggle to support a warm-winter fishery. Balch is not deep enough to provide significant dissolved oxygen levels that would support trout but is plenty deep enough to support a healthy warm-water fishery, as anyone who fishes on Balch can attest. Given the profile of Balch, we are not undertaking any dissolved oxygen measurements at this time. It should be noted that New Hampshire conducted a two-year trout-stocking program on Balch in the 1950’s because the water quality was excellent but discontinued it because the stocked fish did not survive the winter due to lack of dissolved oxygen.

If you’d like more information on the BLIMP water quality monitoring program, please email john.castellot@tufts.edu. Much of the above is taken from Bob Craycraft (Director, UNH Lay Lakes Monitoring Program) and his excellent “how-to” sampling instructions.  This document also provides you with many key scientific references that provide the basis of our efforts on Balch.

If you would like to volunteer to help us with water sampling, please contact John Castellot at the above email address.