Tales of Stream Monitoring Fun
Lake Accotink Park
Friends of Lake Accotink Park
Friends of Accotink Creek

Friends of Accotink Creek and Friends of Lake Accotink Park hold biological stream monitoring workdays four times per year.
Thanks to all the volunteers who have joined us for this important data-collecting activity!

December 13, 2014 Stream Monitoring:

A larger-than-usual turnout of 20 volunteers was met by a larger-than-usual collection of 1051 invertebrates. The weather cooperated with a sunny day, dry and crisp.

We took two nets, but it turned out one would have sufficed. While the invertebrate numbers were high, the variety of species was low, with the overwhelming bulk of the invertebrates collected being common netspinner caddis flies and aquatic worms. Both these species are tolerant of impaired waters and their abundance is not a good sign for Accotink Creek. As usual, the stream health score was 4, in the unacceptable range.

The imbalance in the health of the invertebrate population is the motive for the current TMDL study of means to improve the health of Accotink Creek.

See the rest of the photos of the day here.

Our September 13, 2014 Stream monitoring:

Cloudy skies greeted our band of stream monitors as the session began. Only a few raindrops fell as we were wrapping up, just enough to get themselves noticed.

Our overall invertebrate numbers were good, with 442 invertebrates captured with just one net. This is encouraging after disappointingly low numbers recently. Also encouraging was the capture of two beetle larvae and one crawling water beetle of the Haliplidae family. Beetles are less tolerant of poor water quality than most of the invertebrates we usually see on Accotink Creek.

The Common Netspinner caddisfly, a tolerant species, dominated our catch today, being 338 of the total. The tally of species, when entered into the stream health formula, gave Accotink Creek a score of 5, in the unacceptable range as usual. The results of volunteer monitoring are used for official assessment of stream health, as is happening now with the beginning of the Accotink Creek TMDL study.

Sediment resulting from excess runoff from paved surfaces is the major factor degrading the health of our creek. Spare a thought for Accotink Creek in your land use decisions.

Mussel Rescue August 15, 2014:

On August 12 the main USGS stream gauge on Accotink Creek began the day with a reading of 3.6 cubic feet per second. After hours of pouring rain in the afternoon it had jumped to 2430 cfs, high enough to send the creek over its banks. It then dropped back down to 172 cfs by midnight.

By August 15, the waters had receded enough to permit a search for mussels stranded when high water pushed them out of the stream bed. Volunteers from FLAP and Friends of Accotink Creek joined together to scour the gravel bars downstream from the dam, which is the only part of Accotink Creek where a reduced population of freshwater mussels still hangs onto a small part of their historic habitat.

Nineteen mussels were located high and dry or in shallow waters that were soon to dry out. Returned to the main channel, we hope they will continue to live out the remainder of their 80-year lifespan and produce succeeding generations. Eliptio complanata is the sole freshwater mussel species still found in Accotink Creek.

The rescue party also netted a number of small fish of several different species stranded in puddles and returned them to the creek.

See the rest of the mussel portraits here.    Learn more about freshwater mussels.

Our June 14, 2014 stream monitoring:

Rain threatened, but stayed away, as a minimal band of three dedicated monitors kept alive the long running collection of important data on the health of Accotink Creek. Three is not enough! Your creek needs you! Join Team Accotink by participating as a committed bug and data collector. Join Team Accotink Now!

It was Midge Madness day, as our catch was overwhelmingly dominated by tiny squiggling midge larvae, making up 82% of the catch. The midges saved the day, compensating for the disappointingly low numbers of other invertebrates found.

It took two nets to reach the minimum quota of 200 invertebrates, an improvement over the four nets we have had to set at each session for over a year. Still, this is a far cry from the one single net that used to suffice just a few years ago.

The scoring formula gave Accotink Creek a rating of 5 on a scale of 12, which is down in the "unacceptable" range. The score was nudged slightly upward from our usual 4 by the high percentage of insects (midges).

Erosion and sediment caused by paved surface runoff are what are holding Accotink Creek down by making life difficult for the vital invertebrates at the base of the food chain.

Heavy rain April 29 & 30 pushed Accotink Creek over its banks with enough force to displace and strand freshwater mussels. Scouting on May 2 showed the water was generally still too high to reveal the gravel banks upon which mussels become stranded, but a few individuals were already exposed. Returning on May 5, the creek was back down to near average flow and 36 live mussels were found and returned to safety.

Another deluge on May 15 required a second rescue on May 19 that returned 33 mussels to the refuge of deeper water.

River mussels in Accotink Creek, of the single species Eliptio complanata, were once abundant, but now are found only in reduced numbers and only in one stretch of the creek, below the Lake Accotink dam. The major enemy of mussels, as with most aquatic life in Accotink Creek, is smothering fine sediment, the result of streambank erosion caused by excess peak runoff from paved surfaces.

If when I stand before the seat of final judgment I can say:

• I accepted life without complaint,
• I harmed no fellow living thing,
• I lived each day in service to all around me,
• And perhaps once in a great while, I brought forth a pearl,

Let us not let these fellow creatures be sent to that judgment before their times. Care about Accotink Creek.

See the rest of the mussel portraits here.    Learn more about freshwater mussels.

Our March 8, 2014 stream monitoring:

A break in the snowy weather and warming temperatures made for a fine day of biological monitoring along Accotink Creek.

Turnout of volunteers was high, with twenty one volunteers of all ages, including contingents of future naturalists from Fairfax High School Envirothon and the Annandale High School Green Atoms.

We captured one scud, a type of tiny shrimp-like crustacean, a rather unusual find at this location. Another unusual find was an aquatic sowbug, related to the familiar "roly-poly" found under stones and logs.

The bulk of the catch this time was many aquatic worms, followed in number by invasive alien Asiatic clams, both species tolerant of poor habitat conditions. After all the invertebrates were counted and cataloged, the stream health scoring formula gave Accotink Creek a rating of 4 on a scale of 12. This is a typical score here, and puts Accotink Creek in its usual unacceptable score range. Sedimentation needs to be brought under control before we can hope for much improvement.

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