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 decades.

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 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

The lake is located in a county that is a leader in agricultural land use and milk production and in a state where agriculture is the largest commercial industry and the largest single land use. Lake Linganore likely is no exception to the United State Environmental Protection Agency’s (USEPA’s) 2000 findings from a 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: algae nutrients; sedimentation; and bacteria.

Algae & Algae Nutrients

Algae is a normal and healthy component of fresh lake water. However, when excessive algae growth occurs, it can be unhealthy for the lake. When this occurs, algae sinks to the lake bottom after they die, where bacteria decompose them. The bacteria consume dissolved oxygen in the water while decomposing the dead algae. Fish kills and foul odors may result if dissolved oxygen levels drop. Additionally, under certain conditions blue-green algae (a bacteria) may arise, which can be problematic as they may produce toxins (like red tide). Excessive algae growth is often fueled by the abundance nitrogen and phosphorus compounds that are used in fertilizers and also found in animal wastes (manure and urine).

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. 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.

To help evaluate the degree of algae nutrients present in the lake water and its tributaries, WQ has been collecting / analyzing samples and studying monthly lake and tributary algae nutrient and bacteria data published by the DPW (https://frederickcountymd.gov/index.aspx?nid=5168). Monthly, during a year-long study spanning 2013 – 2014, the two main lake tributaries, Linganore Creek and Bens Branch, were tested by WQ volunteers for flow rate and for nitrogen and phosphorus content. Additionally, during the warmer months in 2013, Hood College completed several surveys of the type of algae present in the lake and assessed dissolved oxygen and temperature depth profiles. On three separate occasions in 2014 and 2015, WQ volunteers sampled stream discharges from 17 smaller component sub-watersheds together comprising the larger Lake Linganore watershed to identify watershed locales which stood out as significant contributors of the algae nutrients.

Water Qualty_Algae

Key conclusions from the sampling / analyses conducted to date:

  • There is ample nitrogen and phosphorus in the lake and tributaries to support / promote algae growth;
  • Nitrogen concentrations in Linganore Creek have been significantly higher than in Lake Linganore, indicating an-ongoing source(s) from the watershed;
  • Algae growth appears to be limited by the availability of phosphorus;
  • Phosphorus released from the bottom sediments mixes with shallower water as temperatures equalize through the lake water column;
  • The predominate algae observed in the lake during the summer are species common in nutrient-rich waters. Hood College has reported finding Microcystis, a blue-green algae in Lake Linganore;
  • Algal photosynthesis causes very high oxygen levels in the surface waters;
  • Bottom water (below ~10 feet) are anoxic (without oxygen) throughout the summer.
  • The most significant nitrogen and phosphorus mass loadings to the lake are believed to occur during storm events, periods of time when it is unsafe for WQ volunteers to collect samples and measure stream flow;
  • Maryland has set higher goals for Lake Linganore water clarity and quality than the county has been able to achieve to date.

The results of the component sub-watershed sampling were presented to the community.

Sedimentation

Sedimentation of fresh water lakes normally occurs as natural erosion, transport and deposition takes place. Natural sedimentation rates can be accelerated when land development occurs and / or when there is inadequate undisturbed vegetated corridors (riparian zones) along waterways. Development is normally associated with increased run-off / reduced infiltration, which leads to increased surface water flow rates and erosion. 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. Sediments have not yet been removed / dredged from Lake Linganore since it was formed more than 42 years ago, but plans are currently underway to remove a substantial volume of lake sediments (https://www.lakelinganore.org/lake-dredging/).

Too much sediment coming into the lake and building up not only results in loss of water storage reduced recreational use (e.g., loss of navigable waters) but also could potentially play a role in too much lake 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 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. The USGS recently found that due to sedimentation, the upper portion of Lake Linganore (above Boyers Mill Bridge) has lost 65% of its water storage capacity and the lower portion has lost 17% of its water storage capacity. The sedimentation pattern 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 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, therefore have devised E. coli standards for public beaches to minimize human health risks. Maryland’s standard for public “designated bathing beaches” is an average (geometric mean) E coli concentration of 126 MPN / 100 milliliters. In addition to the average standard, Maryland also has a location-specific one-day maximum standard, which would amount to 459 MPN/100 milliliters for Lake Linganore.

To better understand lake bacteria and communicate this information to residents, WQ instituted a summer daily lake water sampling / bacteria analysis program for the Lake Linganore beaches in 2013. The daily summer beach sampling program has continued annually. During 2016, the sample analysis was expanded to include a field screening test for cyanobacteria (see below). All beach samples are analyzed and results 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.

Over the past 3 consecutive years, the average (geometric mean) E. coli levels met Maryland’s public beach standards with significant margin. However, Maryland’s maximum daily threshold was exceeded on several days during each of the 2013, 2014, and 2015 summer seasons. 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.

Another key finding has been 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 finding points of off-site source(s) of bacteria flow into the lake and become diluted.

Cyanobacteria – blue green algae
In 2016, Frederick County, the City of Frederick, Hood College, Center for Coastal and Watershed Studies, LLA and Friends of the Lake, Water Qualty began collaborating on a study of Lake Anita Louise and the waters that flow into the lake. The study was prompted by the unexpected proliferation of Planktothrix rubescens, an algae-like bacteria that gave Lake Anita Louise a reddish hue beginning late December 2015 until the lake froze over after the January 22-24, 2016 blizzard. Planktothrix rubescens is a naturally occurring bacteria normally associated with colder, alpine lakes as it does not survive in summer water temperatures in the mid-70s. This bacteria has also been observed in recent years in the pond at Fountain Rock Park and Nature Center in Walkersville. The concern with this bacteria is that when disturbed or when it dies, the bacteria can produce a toxin in water that can be harmful to pets and humans, if ingested or otherwise internalized. Frederick County and City are particularly interested since Lake Anita Louise flows into Lake Linganore, a drinking water reservoir for both the county and the city. In addition to cold water temperatures, Planktothrix rubescens needs abundant nitrogen and phosphorus to thrive like other cyanobacteria or “blue-green algae”. Therefore, initial studies will include sampling of Lake Anita Louise and its tributaries for nitrogen, phosphorus, select bacteria, temperature, pH and other parameters to determine if point sources of excess nutrients can be identified that may have contributed to the algae-like winter bloom.

Beginning in 2016, daily Lake Linganore beach samples collected during the summer are also screened using field instrumentation for indications of cyanobacteria (including Planktothrix and Microcystis) and reported together with the E. coli results at https://www.lakelinganore.org/test-results//.

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.). The WQC has no lake-specific information on this amoeba as it relates to Lake Linganore other than that there has been no documented case of an infection of the amoeba over the 42-year 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.