Lovettsville’s David Ward and Chris VanVlack combined their talents to report on the County’s Water Resources based on samples from 2015. The report sums up the county’s precipitation, streamflow, groundwater flows, and surface and groundwater.
While the population of the county is over 364,000, it is expected that by about 2030, there will be 467,000 persons. When it comes to water quality, population density is not irrelevant.
The county has about 1,500 miles of perennial streams and it’s by knowing how much water flows and how much the flow varies over both short and long periods that one may assess floodplains, flood control, water structures, and environmental conditions. Stream gauges measure these stream characteristics and the results are forwarded by telemetry to the USGS – and can be found on the USGS web site for Loudoun County.
One such measurement is daily flow rate in Goose Creek near Leesburg that shows the rise and fall of the flow that is most affected, in the case of Goose Creek, by the rainfall at Dulles airport.
There are more than 14,500 active water supply wells in Loudoun. In fact, groundwater is the primary source of drinking water for the majority of residents in western Loudoun. There are wells that the County monitors for well depth (from 165 feet to 700 feet), rock type involved (fluvial, igneous intrusive, plutonic, etc.), and pairing the high and low points of the groundwater in each well.
The quality of the county’s water is measured using various metrics including chemical, microbiological and benthic macroinvertebrates.
Nutrient enrichment is a major cause of stream impairments and can cause low dissolved oxygen, fish kills, shifts in flora and fauna and nuisance algae. More than half of the samples collected contained high nitrogen and phosphorous concentrations.
In sampling for e coli pathogens 80 percent were above the limit for the recreation use of water. There are programs in place to reduce bacterial contamination including initiatives to repair or upgrade on site wastewater treatment systems.
Small organisms (mostly insect larvae) indicate by their tolerance of the water the quality of the water. This sampling indicated those streams that were excellent and those under extreme stress.
There are also large areas of the county that have elevated levels of iron and manganese, considered “aesthetic contaminants” as they do not adversely affect human health at the concentrations found in the county.
The one significant groundwater contamination in the entire county is the Hidden Lane Landfill in Northeast Loudoun and is on the EPA’s National Priorities List.
The most prevalent sources of potential groundwater pollution are the on-site wastewater treatment systems serving homes and small business in the rural areas of the county. There are about 15,000 such systems in the county. If properly installed, these systems are fine. But they are not all installed well or maintained properly. The report encourages testing to assure that these systems are functioning properly.
We have all been put on notice by what happened in Flint, Michigan that lead dissolves and contaminates water. Studies have shown there are a range of wells in the aggressive range of corrosivity that merit testing. The report identified Langelier Index values that indicate the degree of corrosivity. The overlay of lead presence on a geological mapping showed no correlation.
The recommended remedy is to have water samples taken to test private wells and not just for lead corrosivity.
In short, the report is both interesting and important. It confirms the need for vigilance among homeowners and businesses in an ever increasingly denser county in order to assure the quality of our water.
The report can be accessed at https://www.loudoun.gov/DocumentCenter/View/126214.
District Director at the Loudoun Soil & Water Conservation District
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