Water Quality

Water Qualty_Who We Are

Water Quality

Chair:

Eric Roberts
ericroberts.excalibur@comcast.net

Lake Linganore Water Background

Lake Linganore water is used as the primary source of drinking water for the City of Frederick and is the emergency back-up water supply for Frederick County. It currently holds over 500-million gallons of water, nearly a 4-month drinking water supply for the City of Frederick. The lake water comes from a ~80-square mile watershed roughly bounded by Mount Airy to the southeast, Taylorsville to the northeast, Libertytown to the northwest and New Market to the southwest. Water enters the lake through the two primary tributaries, Linganore Creek and Ben’s Branch, and leaves via the dam’s spillway at an average rate of more than 600 gallons per second, a flow that would fill an Olympic swimming pool in less than 20 minutes. While the Lake Linganore private community holds title to the land beneath and around the water, the water itself is public property. Members of the Lake Linganore community have been enjoying the waters of Lake Linganore for swimming, boating, fishing and other recreational purposes for half a century.

Since Linganore Creek was dammed to create the lake in 1972, agricultural management practices in the Lake Linganore watershed have improved to help reduce harmful chemical applications to crops / fields and minimize livestock encroachment in tributaries and control run-off.   Despite these better agriculture management practices, population growth & deforestation / development has added new stresses to the environment and there continues to be room for further improvement of Lake Linganore water quality much like many freshwater lakes.

What Quality Focus

There are four lakes in the Lake Linganore community.  By far, the largest is the community’s namesake.  The smaller lakes are Lake Merle, Lake Anita Louise and Lake Marion.     Our lakes are in an agricultural county with a substantial dairy industry in a state where agriculture is the largest commercial industry and the largest single land use.   The United State Environmental Protection Agency’s (USEPA’s) found in a 2000 study of the nation’s lakes that agriculture is the most wide-spread source of damage to lake quality.   Algae nutrients and sedimentation were listed in the USEPA study as the top identified pollutants and stressors to U.S. freshwater lakes. Because of the agricultural land use of the Lake Linganore watershed and lake water quality observations, Friends of the Lake, Water Quality (WQ) has been focused on three main water quality concerns on LLA’s behalf: algae & nutrients; sedimentation; and bacteria.

Algae, Blue-Green Algae & Algae Nutrients

Algae is a normal and healthy component of fresh lake water. However, excessive algae growth can be unhealthy for the lake.   Excessive algae can sink to the lake bottom, where the algae is subject to bacterial decomposition.  In the process, the bacteria consume the lake’s dissolved oxygen depleting the lower depths of oxygen needed to support aquatic life.  Fish kills and foul odors may result.  The low oxygen conditions at the bottom also liberates phosphorus bound to the bottom sediments which can fuel further algae growth.   Additionally, under certain conditions blue-green algae (a cyanobacteria) may proliferate.  This can be problematic because certain forms of cyanobacteria may produce toxins (like red tides).

The relative abundance of cyanobacteria in our lakes typically increases through the warmer months into the late fall.     Although the lake bottom sediments are an ample reservoir of algae-fueling phosphorus, additional nitrogen and phosphorus compounds (originating from fertilizers, manure, etc.) are washed into the lakes with sediments during storm water events.

Because excess algae build up can also cause problems in treating water for drinking water distribution in the City of Frederick, the Department of Public Works (DPW) normally treats Lake Linganore once per year during the summer with copper sulfate. Copper algaecides have generally been used in reservoirs for more than a century when harmful algae and cyanobacteria achieve high densities, produce toxins, or produce taste and odor compounds that pose risks or interfere with the uses of water resources.   Copper algaecides interfere with the ability of algal cells to respire, photosynthesize, and, at some concentrations, maintain cell integrity.   LLA normally announces when the treatment is to occur well ahead of time. More information about this annual treatment can be found through inquires to DPW.

Between Memorial Day and Labor Day, daily sampling of Lake Linganore beach water.  This includes screening the samples for indications of excessive cyanobacteria.  The samples are field screened with an instrument designed to detect relative levels of phycocyanin (PC), a surrogate for cyanobacteria.  If the PC reading is elevated, the Maryland Department of the Environment (MDE) has helped collect and analyze samples for cyanobacteria toxins upon request.

Additional monthly monitoring of algae and other parameters at Farm Pond, Lake Anita Louise, Lake Merle and Lake Linganore is completed for LLA by Hood College students and staff.   Lake water samples are screened for chlorophyl and PC and they are examined to identify the main species & abundance of algae and cyanobacteria in the waters.   If certain criteria signal abundance of cyanobacteria, Hood will run a preliminary toxin screening test.  Depending on the results of this screening test, MDE may be requested to perform more quantitative analyses of lake water samples.

Frederick County (Department of Public Works) also conducts monthly e and tributary algae nutrient and E. coli bacteria data.  Historical and current county data are published online at https://www.frederickcountymd.gov/1288/Regulatory-Compliance.

LLA is currently experimenting with a safer, lower energy, lower cost and more natural means of limiting cyanobacteria abundance in its lakes through the recreational season.   In 2021, it deployed barley straw bales along the perimeter of Lake Anita Louise and upstream Farm Pond (feed waters to Lake Anita Louise).   Barley straw decomposition in contact with lake water and sunlight is reported to produce certain phenolic compounds that naturally inhibit cyanobacteria growth.  If the Lake Anita Louise barley straw pilot study proves successful in 2021 the results will likely be replicated in subsequent years before being tested in other community waters.

Water Qualty_Algae

Sedimentation

Sedimentation and infilling of freshwater lakes is a normal occurrence. It stems from natural erosion processes, sediment transport in surface waters and lake deposition. Natural sedimentation rates are accelerated when land development occurs and when there are inadequate undisturbed vegetated corridors (riparian zones) along waterways. Deforestation and development results in more impervious surfaces (e.g., roads, roofs, lawns, etc.) which limits infiltration and causes increased run-off and leads to increased surface water flow rates and erosion. Reduced infiltration not only delivers more sediment (with phosphorus) to our lakes but other contaminants (e.g., salt, tire particles, asphalt compounds, petroleum hydrocarbons, pesticides / herbicides, surfactants, etc.). More and more discoveries are emerging about contaminants entering waterways and their harmful effects. For example, in late 2020, Science, a reputable peer-reviewed scientific journal, published a study linking the chemical 6PPD, a common rubber antioxidant chemical found in tire preservatives, to Coho salmon mortality in the Pacific Northwest. Improper installation of or failures of erosion control measures during deforestation and development work has also impacted our lakes.

Man-made lakes such as Lake Linganore require periodic (e.g., 10-15 years) sediment removal in order to keep them viable for drinking water storage and recreational use. Until 2019, sediments had not yet been removed / dredged from Lake Linganore since it was formed more than 42 years ago. None of the other community lakes have ever been dredged.

Too much sediment coming into the lakes and building up not only results in loss of water storage and reduced recreational use (e.g., loss of navigable waters) but can also contribute to excessive algae production. Phosphorus binds to soil particles so the more sediment that moves into the lake the more phosphorus is delivered to the lake that can be used to fuel lake algae growth. The increased water temperature of infilled, shallower lakes also promotes algae.

The average sedimentation rate of Lake Linganore is equivalent to about 11 feet of soil stacked on top of a football field each year. Approximately 5 million gallons of water storage capacity are lost to sediment annually. Before the 2019-2021 dredging of Lake Linganore, the USGS had found that sedimentation caused the upper portion of Lake Linganore (above Boyers Mill Bridge) to have lost 65% of its water storage capacity and the lower portion lost 17% of its water storage capacity (only a portion of only the upper half of Lake Linganore has been dredged) . The sedimentation pattern in Lake Linganore indicates that that the bulk of the sediments entering and settling in the lake are coming from outside the community (upstream). To begin assessing whether the sediment might be coming from specific portions of the watershed, WQ volunteers in 2014 & 2015 sampled stream discharges from 17 sub-watersheds within the Lake Linganore watershed and samples were analyzed by Hood College for suspended solids. The study presented to the community revealed several localities of concern in the watershed, but further study (e.g., under storm conditions) is needed.

Bacteria and Other Microorganisms

E. coli
Bacteria and other microorganisms are ever-present in the environment and the lake waters in our community are no exception. A bacteria testing parameter that is used to evaluate the likely presence of potentially harmful bacteria in recreational and drinking waters is the E. coli test. E. coli or Escherichia coli is a type of bacteria commonly found in the intestines and wastes of healthy warm-blooded animals (humans included). There are more than 100 different strains of E. coli, and most are harmless. E. coli O157:H7 is one strain of E. coli (usually associated with cattle, but has found in the intestines of deer, goats and sheep) that can cause illness to humans. E. coli is an accepted indicator of the possible presence of bacteria or viruses in water which could cause illness. The test used for E. coli is far less expensive and more reliable than other tests.

Because E. coli is both naturally occurring within the wildlife, in domesticated animals and in humans, it is commonly present in tributary and lake waters. States like Maryland have devised E. coli standards for public beaches to minimize human health risks. Maryland’s public beach Beach Action Value (BAV) is 235 MPN/100 milliliters.

From 2013 through at least 2021, LLA has been monitoring and communicating daily Lake Linganore beach bacteria conditions during the summer recreational season. All beach samples are analyzed by a Maryland laboratory and the analytical results are posted on the LLA web site (https://www.lakelinganore.org/test-results/) within 24 hours to allow LLA members to make informed decisions when using the lake for recreational purposes. The daily results can also be found on Facebook at “Friends of the Lake • Lake Linganore at Eaglehead”. Daily posted information includes:

• Blue-green algae (cyanobacteria) field screen
• Prior day lake bacteria concentrations
• FAQs about E. coli
• Maryland public beach standards
• Red / green flag

Over 5 consecutive years of monitoring (2013 – 2017) the geometric mean E. coli concentration of Lake Linganore during the summer season ranged from 26 MPN / 100 milliliters (2017) to 39 MPN / 100 milliliters (2013), a range that is well below Maryland’s mean standard of 126 MPN / 100 milliliters. During these same five years, the number of days that E. Coli exceeded Maryland’s BAV ranged from 7 days (2014) to 22 days (2013) with an average of 13 days / season.

Higher levels of E. coli are temporary and appear to be associated with heavy (more than 0.4-inches) precipitation events. Extended dry periods are associated with sustained and consistent low levels of E. coli.

Historical testing of Lake Linganore and its two main tributaries have found that bacteria levels in Linganore Creek have been on average 4 to 9 times higher than in Lake Linganore and the bacteria levels in Ben’s Branch have been 2 to 3 times higher than in Lake Linganore. These data suggest that watershed source(s) of bacteria are brought into the lake by the tributaries and become diluted and die off.

Naegleria fowleri
National news media periodically reports on infection from amoeba Naegleria fowleri elsewhere in the U.S. (more commonly in the warm waters of the southern U.S.).   There has been no documented case of an infection of the amoeba over the half-century history of Lake Linganore. According to the Center for Disease Control (CDC), “…there have been 34 reported infections in the U.S. in the 10 years from 2004 to 2013, despite millions of recreational water exposures each year. By comparison, in the ten years from 2001 to 2010, there were more than 34,000 drowning deaths in the U.S.”. Based on this statistic, Naegleria fowleri infection appears to be a low-risk concern anywhere in the U.S. as there’s a 1,000 times greater chance of drowning than of being infected by this amoeba. More information concerning this amoeba can be found at the CDC web site http://www.cdc.gov/parasites/naegleria/general.html.

Spring Spawning Fish Kills
There are lots of things that can kill fish but the vast majority of spring fish-kills in our locale are related to a natural spawning cycle.   Spawning is stressful to the fish and can lead to substantial fish mortality.   Sunfish are particularly susceptible since they often nest in shallow water subject to daily and weekly fluctuations in oxygen and temperature.   They do not eat during this period while, at the same time, they must defend the nests against other fish. The energy balance just does not work out in some cases, and some fish die. If we have extremely variable weather, the stress is often greater.

If a spring fish-kill consists of one species, all of similar size, most commonly 5-6 inch sunfish, the fish kill is almost certainly a spawning mortality.   On the other hand, if the kill involves multiple species or a wide range of sizes (e.g., if 100 fish of multiple species are found in a short time span), that might suggest something more than typical die off which, therefore, might be worth investigating and reporting.

Lake Water Scums
A resurgence of flora and fauna occurs in our lakes during the warmer months.   Lake water surface coatings are a manifestation of this resurgence as is a reduction in water clarity and a return of the characteristic olive-green hues.  The coating become particularly evident when the air and water is still.      Many of us not only find these naturally occurring scums uninviting but sometimes alarming.  We often wonder what the scums are and what they might be signaling.

The surface scums you may soon be seeing in our lakes are most likely harmless evidence of a flourishing biota.  Such harmless scums may include pollen, duckweed and various green algae.  However, some lake water scums (e.g., cyanobacteria) can be harmful if they have produced toxins and, therefore, you should avoid contacting any lake water scums and your pets should be kept away.   More specifically, LLA advises residence to follow the Centers for Disease Control (CDC) recommendations when it comes to any algae, scum or coating on the surfaces of our lakes:

  • Avoiding swimming or boating in areas where the water is discolored or where you see foam, scum, or mats of algae on the water; and
  • Don’t let pets swim in or drink from areas where the water is discolored or where you see foam, scum, or mats of algae on the water. If pets (especially dogs) swim in scummy water, rinse them off immediately—do not let them lick the algae (and toxins) off their fur.