Since April 2010, NNWB’s Glenn Welch has led a macro-invertebrate monitoring team 4 times a year on the Northwest Branch near the Kemp Mill Trail Head. In more recent years the team added another site farther upstream, in the Sandy Spring area. If you would like to observe, please contact Glenn.Welch@yahoo.com.
Following a protocol developed by Nature Forward (previously Audubon Naturalist Society), the team disturbs the stream bed--especially in riffles and under rocks--and collects in a net whatever floats in. They take 20 net collections and transfer findings to a small tub.
The team examines and identifies the small animals without a backbone (benthic macro-invertebrate) using a microscope. They determine how many individuals of each type they found, and stop upon reaching 100. Findings are then returned alive to the stream.
There are three orders of insect larva that when present can indicate a healthy stream, these are mayflies (pictured), stoneflies and caddisflies.
We of course find crayfish, and larval forms of dragonflies, damselfies, beetles, true flies and others. We count and tally them all.
The health of a stream can be determined by the critters able to live there: Some require very clean water; another group can tolerate relatively poor water quality; and a third group lies in between. The Northwest Branch in lower Montgomery County is in the fair to poor range. Our mission continues to be to improve the health of our streams.
While Glenn and his team assessed stream life at the Kemp Mill and Sandy Spring sites, a team led by Gregg Trilling of Nature Forward collected samples and engaged the public at Adelphi Mill in Prince George's County. The adjacent trail greatly facilitates public engagement.
Photos by NNWB ambassador A. Ambler.
The operation begins with netting those critters hiding under the rocks and in the riffles.
Collecting invertebrates from the stream bed.
Wow ! A dragonfly larva
The water was very calm. We collected our samples while crouching on the sand bar at the right edge of the picture and on the adjacent rock. Analysis showed our E-coli counts to be just 36.9 and 38.4 mpn/100mL, the lowest by far of the 5 sites sampled. (The other sites are on Long Branch and Sligo Creek.) If the E-coli level stayed like that, swimming would be safe. But unfortunately, after a rain, E-coli levels rise. 5/19/21
Perched on a rock, Anne shows the turbidity sample. We also check the acidity level and water temperature vs air temperature. Sampling will continue every 2 weeks, and at the end of the summer we'll have a profile of stream quality. 5/19/21
Bacteria samples must be kept on ice and analyzed within 5 hours from collection, so it's a race against time to turn in the samples.5/19/21
That's a thermometer she is holding over the water. 6/2/21
The water turned out to be a shade warmer than the air. Perhaps hot water running off pavement? 6/2/21
The bacteria sample must be analyzed within 5 hours, so the label must have time as well as date. The e-coli level, averaged between 2 samples, was 249 MPN/100 mL, still passing, but higher than on 5/19. 6/2/21
Monitors also must fill out a chain of custody form. 6/2/21
They compare the pH strip color to the coding. The water was more alkaline than at the testing 2 weeks earlier. 6/2/21
After a dry period, the e-coli level at our monitoring site was very good. Kem holds the monitoring kit with ice packs and the clip board for recording our data. 6/30/21
The Anacostia Riverkeeper program expanded this summer (2023) to include a Northwest Branch site in Prince George's County at 38th St. as well as the Burnt Mills site in Montgomery monitored the previous 2 years. When the program first began, in summer 2020, the NWB site was in Prince George's County, at Lane Manor Park.