December 2018

Posted by: upperwalnutcreekaustin | December 16, 2018

December 2018

December 15 – a beautiful day. Not a cloud in the sky and at 55 degrees it was cool but not cold. A week ago we had nearly 3″ of rain and none since. The result is an incredibly clear stream. The sample site is the clearest we’ve ever seen it, as shown below in the photos. Nearby we saw a mamma turtle with 3 babies, but not fish or birds, including pigeons, whose droppings are a possible source of e-coli.

The stream had mostly returned to its usual height, though the flow was still strong from the culvert and the water was spilling over the waterfall nearly all the way across and gurgling loudly, as was the culvert’s stream. And the inlet above the waterfall had a bit of water in it. There was no surface algae, although there was a significant amount of long submerged algae strands above the waterfall. It looked like the “sometime island” rocks further upstream were just above the water level but I didn’t get close enough to confirm.

The trail crossing downstream of the bridge was mostly covered by the stream. There were a couple of rocks for steps but most of them were gone, possibly by a strongly flowing stream during/after the 3″ of rain. And the nearby gravel bar was small.

The water was definitely cold (51 degrees) and as we expected, at 10.2 the dissolved oxygen was the highest we’ve seen in a long time. The e-coli counts were very low, at 3 ML the sample site was only 33 colonies and the control site was double that.

Observations:

Air temp 13 C (55 F)
Water temp 10.5 C (51 F)
Dissolved oxygen 10.2 (about 90% saturation)
Specific conductance 560
pH 7.0
Transparency > 1.2 meters
Nitrate <0.3