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Rivanna River receives largely average grades on health report card

The Rivanna River is doing just average, according to a recent health report card from the Rivanna Conservation Alliance.

The Rivanna Conservation Alliance, or RCA, is a nonprofit watershed organization created to help monitor, clean and protect the Rivanna River and its tributaries. It was formed in 2016 through a merger between the Rivanna Conservation Society and StreamWatch.

The report card, which compiles data from 2015 to 2020, graded the river based on the presence of E. coli bacteria and organisms in samples gathered from 50 sites throughout the river’s watershed. E. coli is considered dangerous and can cause disease in humans and other animals.

Weekly E. coli bacteria samples collected by RCA’s approximately 120 volunteer water quality throughout the period studied. Virginia’s water quality standard for E. coli is 410 bacteria colonies per 100mL of water. Streams meet the standard if at least 90 percent of water samples are lower than 410 MPN.

The watersheds were broken into five areas, with South Fork Rivanna subwatershed one and Lower Rivanna watershed each receiving a “B” ranking and the South Fork Rivanna subwatershed two, North Fork Rivanna watershed and Middle Rivanna watershed each receiving a “C” ranking. The “B” ranking indicates that streams scored 60.0 or higher, meeting Virginia’s water quality standard. This is the first time the river has been scored by the RCA.

The lower ranked watersheds are all clustered closer to Charlottesville and the more densely populated portions of the area.

According to Rachel Pence, manager of the monitoring program, each spring and fall volunteers head to the sites to catch, identify and count the different small organisms that inhabit the bottoms of rivers and streams.

Specifically, Pence said the organisms the RCA is looking for are called benthic macroinvertebrates — benthic meaning bottom dwelling, macro meaning that they can be observed with the naked eye and invertebrate meaning they have no backbone. That includes things like mayflies, stoneflies, caddisflies, crawfish, clams and snails, among other organisms, Pence said.

“Healthy streams have really well balanced populations that have a lot of different types of organisms living in it and they all have different pollution tolerance values, or they have different sensitivities, to different impairments to pollutants,” she said. “Some are more sensitive to things like low dissolved oxygen, high sediment loads, organic pollution, things like that, so the organisms that we find really tell us a story about how healthy or unhealthy a stream is.”

Stream health is important because it affects overall ecosystem health, Pence said, and organisms — specifically bugs — in streams are food for animals both in the water and on land.

“Bugs are often overlooked because they’re not as charismatic as fish for some people, but they’re an incredibly important part of the food chain,” she said. “They’re the base of the food chain and they’re relied on by so many different organisms. So it’s important that we work to protect our rivers and streams for a lot of different organisms, but especially for the bugs, because food chain collapses certainly would certainly occur without them.”

The data is used by the Department of Environmental Quality to help screen different sites for further investigation, Pence said. However, even without DEQ insight, she said the organisms collected can give a good sense of the pollutants that are degrading certain streams.

“For example, if we see a lot of things like midges, net spinning caddisflies and aquatic worms in the stream then that can indicate there might be an issue related to low dissolved oxygen because those organisms can withstand low oxygen conditions.”

Midges are the larvae form of true flies and caddisflies are a similar form of insect known in part for their aquatic larvae.

Among the biggest pollutants the RCA is seeing in the river is nitrogen, phosphorus and sediment, the last of which Pence said is often not thought of as a pollutant by the general population.

Pet waste is a big issue in terms of E. coli, Pence said. It’s important that pet owners pick up after their pets and then dispose of it properly. Another source of E. coli is livestock, which Pence said can be offset by fencing livestock out of streams and streamside areas.

“But a really, really important way to reduce bacteria is to plant trees and shrubbery along streams to help filter that runoff, fixing leaking sewer pipes and maintaining septic systems,” Pence said. “In the city, we don’t have a lot of homes connected to septic systems, but certainly out in the county there are a lot of people that are not hooked up to a public sewers, so definitely maintaining septic systems is important.”

Despite the lower ranks received by some areas of the Rivanna watershed, Pence said some sites have improved, which was detailed in a 2020 stream health report. Among those sites that have seen improvements is the Moore’s Creek site downstream from the Rivanna Water and Sewer Authority wastewater treatment plant.

“The timing of the improvements seems to line up really well with a lot of initiatives that they took at the wastewater treatment plant to remove a lot of nutrients from their effluent,” Pence said. “So we seem to be seeing a reflection of improvements in the biology that we’re seeing there just downstream of the wastewater treatment plant and that’s pretty exciting that we’re able to capture an improvement at that site based on our data.”

More information about the RCA’s work and the Rivanna River can be found at rivannariver.org.

Source: www.dailyprogress.com

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