Dear Watershed 3 Fans – thought I would catch you up with some news from the catchment. We had a bit of a dry spell this summer, which was great for all the digging, coring and installing that JP and Maggie B had going on. Zimmer et al. (in review) contains a classification of stream reaches in the catchment as perennial, intermittent and ephemeral, based on three years of observation. This summer, for a week or less, we broke out of that range. On July 27 we observed no flow at any stream sampling site. And there was no detectable seepage at any of the 9 seeps, except for the one not far above the weir (S02), which seemed to be seeping at about the usual rate. At this time, flow over the weir was 0.083′ (pic attached), equivalent to >99% exceedence probability, and seemingly about equal the discharge at S02.
I thought it was interesting that this one seep was the last flowing surface water in the catchment. Equally interesting was that shortly after we made this observation, we had a light rain shower – maybe only about a quarter of an inch – which brought the “perennial” stream reaches back to life. I wouldn’t have thought that such a light rain during dry conditions would have had any response.
JP, Maggie B and I celebrated the low flow by conducting the seventh surface water survey. Six such surveys are reported in Zimmer et al, ranging from 22 sampling sites at low flow (87.5% exceedence probability) to 112 sampling sites at high flow (0.2% exceedence probability). It will be interesting to see what the chemistry looks like for survey number 7 with an n of 1 sampling sites.
Now that I have reported the old news, here is the new news. Yesterday we had our first significant rain of the late summer- well over an inch – which has brought the stream network fully back to life.
– Scott Bailey, reporting from Hubbard Brook