July 2016 monitoring

Posted by: upperwalnutcreekaustin | July 8, 2016

July 2016 monitoring

July 7 – another hot, humid day. We’ve been hovering at or just below the century mark for temperatures for at least a week (seems much longer!), with the heat index up around 108, with no change in site. Typical Texas summer weather. Yuk. Right now 90 sounds cool.

With no rain in nearly a month, the stream has shrunk significantly. As usual this time of year, the site isn’t very attractive. The bases of 3 of the 4 of the bridge columns are dry; the 4th column is nearly dry. The waterfall is still flowing but only in a small section, the rest of it is just stagnant water. There is a good flow from the storm culvert below the waterfall but the main stream has little to no current, and there is only a thin stream on the downstream side of the bridge by the gravel bar, so it’s easy to cross with dry feet. The water surface at the sample site itself, downstream and upstream above the waterfall is scummy. Directly above the waterfall there’s a slightly higher area of rock, which was dry – unusual. Above the waterfall and completely dry inlet, the water level is so low I was able to walk not only all the way to the “sometime island” raised rocks in the middle of the stream above the waterfall but also significantly beyond them. In most sections the dry area on the north side of the stream was 5 ft wide.

Didn’t see or hear any pigeons. Saw a fair amount of minnows at the site and way upstream. And I noticed that although there is some algae around the waterfall area and to the bridge, there is absolutely none – including submerged algae – above the waterfall, all the way up to and beyond the sometime island area. Guess the last heavy rain over a month ago scoured it all away?

The ecoli at the sample site was somewhat higher than preferred for an urban stream (nearly 600 colonies from 3 ML samples); above the storm culvert it was less than half of that. Both are higher than last month’s counts, which was taken soon after the heavy rains. Clearly the flow from the culvert, which includes runoff from the street (pollution, pet waste etc.) has some ecoli in it, and the lack of a noticeable current means the colonies mostly remain in place.

Observations:

air temperature 29 C (84 F)
water temperature 26 C (79 F)
dissolved oxygen 4.0
specific conductance 580
pH 7.0
transparency > 1.2 meters
nitrates 2.0