This spring, during our stream insect collection event known as the River Roundup, HRWC volunteers certainly experienced some of the wettest conditions we have ever seen! The main branch of the Huron was flooding and even some of the smaller tributaries were overflowing their banks. The water was moving fast and conditions were dangerous at many locations. And even though we advertise that people won’t get wet, unfortunately this year I don’t think we were able to keep that promise! Many groups came back from their sampling reporting that they had to stand in knee high water on the bank, and then had to reach their nets down into the quickly flowing main channel in order to find anything! Riffles were missing and many of the bugs had been scoured from gravel and sand stream beds.
Dealing with unusual conditions
Dealing with the results of this sampling, given these conditions, has been a challenge. Since the data gathered from the River Roundup is entered into a long term data set that is meant to show long term trends, it would be improper to use samples that were not collected properly or were taken from a stream that was scoured clean. Such samples would not show if the stream was declining because of human impacts, or lack of habitat, or pollution. Rather, these samples would only tell us that the river was stressed from high flows.
We decided to deal with the River Roundup samples in the following way. First, if a team reported, either orally or on their datasheet, that they were not able to collect the stream insects according to the proper protocol because of high water, we did not record their sample results into the long term database. None of the data was thrown away, rather it was entered into a different database so it can possibly be used in the future if we want to look at the effects of flooding on insect communities.
Additionally, per our quality assurance project plan, if a sample is more than 40% different from the median of the last three samples, this sample is marked as an outlier. Normally in such cases we would revisit the site and determine why the sample was so different. This is an important check since a 40% decline at a site may indicate some type of pollution that we would want to know about. This spring, the outliers were clearly a result of the high flow conditions, the sites were not revisited, and the data was not entered into the long term database.
Samples from 12 river sites, including 4 on Davis Creek, 2 on Portage Creek, and 2 on Fleming Creek, were not included in the long term dataset. Twenty-eight samples were accepted. These were mostly from the smaller tributaries that we monitor. We did not even attempt to monitor our sites on the main branch of the Huron, or lower Mill Creek.
Highlights of April 2011
With the data that we accepted into our long term database, we continue to look for trends that indicate if the biota of a creek is improving or getting worse over time. Here are a few highlights:
1) Millers Creek in northeast Ann Arbor has been given a lot of attention in the past ten years because the stream”s water rises and falls very quickly, causing erosion problems and hurting the insect and fish community. Various groups, including HRWC, the Miller’s Creek Action team, and the City of Ann Arbor have been working to improve the conditions of Millers Creek. I am pleased to report that this spring we found the best sample ever at our Plymouth Road site, even managing to find a stonefly here for the very first time. In the case of this site, the extremely wet weather may have improved its condition since it is not unusual for this creek to dry up under normal weather patterns.
2) Fleming Creek has also been improving in recent years. In particular, volunteers have been finding more and more sensitive insects in the upper portions of the creek, at Warren Road.
3) We have numerous sampling sites throughout the Davis Creek watershed, and unfortunately we are seeing the insects at these sites decline slowly but steadily over time. This is likely a result of the watershed’s biggest yet hardest to detect disturbance, non-source pollution. We will watch Davis Creek closely in future samples.
4) Volunteers at Greenock Creek at Rushton Road found almost three times as many families this April as compared to the past 3 April collections (normally about 5 insect families are found; this year 14 insect families were found). It is possible that the additional water opened up new habitat that is normally unavailable to insects. Whatever the cause, this is a very unusual situation.