The Latest Water Quality Report.
Help Protect New Hampshire’s LakesNH Lakes has an informative guide to wise lake and watershed stewardship. You can view their publication here. The LKWA has created an informative poster outlining some guidlines on being a ‘Good Steward’ of the lake. Download this informative poster for your home or rental property.
The Lake Kanasatka Water Quality Monitoring
2017 Water Quality Data Summary
Reccomendations and ReportsA full report on the lakes water quality was given at our July meeting. You may view a copy of the slide presentation here. Implement Best Management Practices within the Lake Kanasatka watershed to minimize the adverse impacts of polluted runoff and erosion into Lake Kanasatka. Refer to “Landscaping at the Water’s Edge: An Ecological Approach” and “New Hampshire Homeowner’s Guide to Stormwater Management: Do-It-Yourself Stormwater Solutions for Your Home” for more information on how to reduce nutrient loading caused by overland run-off.
Water Quality Connections: How We Can All HelpBy Water Quality Chair Lisa Hutchinson firstname.lastname@example.org Prior to volunteering to test water quality, my sons Andy and Alex were very involved in Science Olympiad in our hometown in Massachusetts. One of the events for several years was Water Quality, Alex was on that team and I was their coach. They won the event at States those years and competed at the National level. From what Alex and I learned as part of that exciting experience, we wholeheartedly support the recommendations on protecting Kanasatka and recognize the importance of Kevin Kelly’s concerns. The Science Olympiad used a nine-part NSF Water Quality Index to determine the health of a body of water. Those nine factors – dissolved oxygen, coliform, pH, biochemical oxygen demand, temperature, phosphates, nitrates, turbidity, and solids – are very much in line with UNH’s LLMP program. And, in fact, they are all inter-related. For instance, an increase in solids, in the form of suspended solids which eventually sink to the lake bottom and dissolved solids (such as phosphorus and other ions) increase turbidity (murkiness) and make the water more ‘tea’ colored. An increase in color raises water temperatures, which if too high doesn’t hold enough oxygen for the fish. Removing shade trees also warms the water. Higher water temperatures increase the rate of decomposition of leaves and other organic materials in the water, further depleting oxygen and increasing the ‘tea’ color. Sound like a vicious cycle?
What can we do as homeowners on or near Kanasatka? Most importantly, we can limit the amount of solids that make their way into the lake. Most common sources are storm-water runoff, construction activity along the shore, fertilizers, soil particles and soil erosion, wastes, and decaying organic matter. Make changes to our properties only with permission and protection – those hay bales and black plastic fences have a real purpose. We can avoid impervious surfaces, and keep the natural features of our land or improve them to handle heavy storm events – roots hold the soil to control erosion, softscapes and plantings and swales hold back the runoff by letting water slow down and soak into the ground instead of carrying soil and organic matter into the lake, foliage shades the water’s edge and helps keep water temperatures in balance. We can make sure we test and empty our septic tanks regularly. We can limit fertilizers and pesticides, they lead to more phosphate in the water than necessary, which becomes dissolved in the water, making it more ‘tea’ colored. Regarding fertilizers, those 3 numbers on the bag or box are N-P-K, or nitrogen-phosphorus-potassium! A green lawn is not healthy for the lake.
Notes from Bob Craycraft
I wanted to follow-up on the question related to the Secchi Disk transparency and color data. In terms of the water transparency measurements, there are three factors in the water column that will impact the water transparency: the amount of algal/microscopic plant growth (which we measure as chlorophyll a and that is collected on the small white filter disks), the amount of dissolved tea colored water (that we receive as filtered water in a 60 ml bottles), and the amount of other particulate debris that can include algal cells, decaying material, inorganic particles such as clay, etc. We do not directly measure the particulate matter but can oftentimes get a sense of its impact based on the data we receive. For instance, if the water transparency changes significantly but the amount of colored water and algal growth remains the same the particulate debris is likely varying and impacting our transparency readings.
It is worth noting that both the chlorophyll and the color samples are collected in the upper warm water layer and that there may be instances during which the Secchi Disk extends deeper into the water column and into the layer where the temperature is rapidly decreasing; the layer of rapidly decreasing water temperature is referred to the metalimnion. Under certain situations, lakes can exhibit a large buildup of algae in the metalimnion and due to the increased density of the cooler water, particulate debris settle out more slowly and can accumulate in this zone. When collecting Secchi Disk transparency measurements in our New Hampshire lakes we typically observe the Secchi Disk becoming fainter and fainter before it is no longer visible. However, in some instances, such as an instance where there is a significant build-up of material in the metalimnion, one can observe an abrupt disappearance of the disk (similar to the visibility difference of an aircraft going into and coming out of a cloud). Historical data collected in Lake Kanasatka have documented large metalimnetic algal populations (e.g. metalimnetic algal populations have been over an order of magnitude higher than corresponding surface water concentrations).
Analysis of data from among our participating lakes has documented varying levels of dissolved color among years and among seasons. Years with above average rainfall are oftentimes associated with elevated color concentrations in our lakes. Lakes that are drained by large wetland complexes are particularly susceptible to pulses of colored water associated with the wet periods or years. The dissolved color is a by-product of the decomposition of organic matter. Many wetlands are particularly colored since they can act as large detention basins where organic matter collects from the terrestrial environment. Wetlands are also oftentimes lush with aquatic vegetation that will die back each fall and contribute to the formation of dissolved colored compounds.
The winter of 2016 was atypically warm with periods of above average weather that contributed to the flushing of wetlands during the winter months. Since water is densest at approximately 4oC (40o Fahrenheight), the lake water temperature is warmest in the deeper waters and coolest immediately below the ice @ 32oF. I suspect the colored water you observed this winter may have been associated with meltwater into Kanasatka that would have flowed over the path of least resistance near the surface waters; the meltwater would have been near 32oF.
We ran a simple regression of median annual color concentrations against median annual Secchi disk transparency and there is a correlation; the Secchi Disk transparency tends to be shallower during years with elevated color concentrations. However, the relationship was not statistically significant. As with many of our lakes, the Lake Kanasatka water clarity appears to be impacted by the amount of colored water. We also ran a regression of median annual chlorophyll a against median annual Secchi Disk transparency. The Secchi Disk transparency tended to be higher during years when the chlorophyll a was lower but that trend was not statistically significant either. I suspect that mid-lake layering impact the Secchi Disk readings significantly on some occasions on Lake Kanasatka. The size and shape of particulate matter also has an interplay in the water clarity. Smaller particles tend to have more surface area to absorb and scatter light than larger particles (all else being held constant).
The varying conditions from week to week and from year to year can add a significant amount of background “noise” to the data and is a reminder that a long-term dataset is useful when trying to distinguish short-term fluctuations from the long-term trends. The extreme weather events certainly add to the data variability among data points. I hope this is useful but if there are still questions that require further clarity let me know and I will follow up accordingly.
As for the classification of Oligotrophic vs Mesotrophic, the water quality has not slipped but has been on the cusp of being mesotrophic since we began sampling. Mid to late season oxygen concentrations near the lake bottom are characteristic of lakes that are further along in the natural lake aging process and Lake Kanasatka has consistently been characterized by low oxygen near the lake bottom. We recently began using a different criteria for the phosphorus threshold that discerns the oligotrophic from mesotrophic lakes and what was formerly considered characteristic of an oligotrophic lake is now considered more characteristic of a mesotrophic lake.
Slide Show Pictures of a visit with the UNH team
on Friday August 4, 2006
Shown are Bob Craycraft, Karen and John, his environmental education students who accompanied him.
The pictures span the collection of different measurements/samples that provide insight into what is going on within the water column (from the surface to the lake bottom). They collect continuous measurements of temperature, oxygen, conductivity (a surrogate for salts), turbidity (particulate matter), pH etc from the surface down to the lake bottom at roughly 0.1 meter (4 inch) increments with submersible probes that are interfaced with a digital logger via a submersible cable.
They also collect water transparency measurements with a standardized 8 inch diameter disk, known as a Secchi Disk, that is lowered into the water column to provide a measure of water clarity. They also have a digital meter that measures underwater light penetration (that acts as a digital Secchi Disk).
They have a sampling device, known as a Van Dorn, that is lowered into the water column and that collects samples at specified depths (generally at the surface, in the middle of the lake and near the lake bottom). I tried to categorize the pictures into the general sampling categories below. ~ Bob Craycraft