Lake Herman: Much Less E. Coli, More Algae

The East Dakota Water Development District has sent out Bacteria Monitoring Project Update #2 to its volunteers (of which this author is one!). The results for Lake Herman are encouraging. After some really ugly E. coli results during our rainy spring, bacteria concentrations in Lake Herman and other area lakes have decreased significantly. In June, only one site on Lake Herman (west side, about 200 meters northwest of the boat ramp, 10 m offshore) exceeded the EPA recommendation for a single sample maximum concentration of coliform-producing units. That means that if the state followed EPA standards (which it doesn't), there was only one spot on Lake Herman where that one reading would have been enough to trigger a no-swim alert or other action. In July, the lake started showing significant algae growth (and smell!), but the E. coli was almost totally gone. By one culture method, not one of the seven sites on Lake Herman showed any coliform producing units; a second test method showed a small amount (20 CFU/100 ml) at one site (the Camp Lakodia tributary). For perspective on that "small amount," that same site produced readings as high as 1800 CFU/100 ml after heavy rain at the beginning of May; the EPA single-sample maximum safety standard is 280 CFU/100 ml. That site has thus cleaned up immensely.

The E. coli results were similar for other area lakes in the bacteria monitoring project. Lake Madison had one E. coli hotspot in June and two in July; Round and Brant Lakes are relatively clean. (For those of you lake readers smelling that green scum, remember, this project is testing solely for coliform bacteria, not algae or the nutrients that help it grow.) Lake Campbell to our north and east showed one hotspot out of seven sites sampled in June and a remarkably high reading (2200-2440 CFU/100 ml) at one other site out of ten sampled in July. Lakes Kampeska and Pelican by Watertown turned up relatively little E. Coli.

Bigger water quality problems lie in the streams that feed the Big Sioux River. Volunteers are taking stream samples at 16 different sites in the Central Big Sioux Watershed, and they are finding E. coli all over the place. According to the update, "About 81% of the sites and 79% of the cultures exceeded the EPA-recommended standard for even infrequent immersion recreation" [emphasis original]. A couple sites, West Pipestone creek and a Beaver Creek tributary, produced samples with bacteria colonies too numerous to count, more than 10,000 CFU/100 ml. Yuck!

Update #2 notes that all of the stream samples taken after rainy weather showed these high E. coli concentrations; the E. coli eases up a bit with dry weather, with 62% of the dry-weather samples showing high E. coli levels. That and the lower results for the lakes through the last couple dry months make sense: one would expect that rain would wash more contaminants from more points away from shore into the water. Spring is wetter, so that's when we can expect more muck and yuck to flow into the lakes.

So for now, Lake Herman's bacteria numbers have improved about as far as we could hope. Time for a swim... if you don't mind all that green stuff in your britches!