August 2019

August 11 – one more hot and humid summer day in Texas. For the last week the temperatures – excluding humidity – have been at or over 100. Add another 5-8 degrees for the humidity effect and in a word, the result is: miserable!

Eight days ago it rained about .2″, and not at all for a week or so before that. So the stream is its usual sluggish summer self. Someone added rocks at the hiking trail to allow walkers to cross with dry feet. The stream is so low there’s no current (flow) at all, it barely trickles through the rocks at the hiking trail. Much further upstream above the waterfall the “sometime island” rocks are dry – I was able to easily walk up to them with dry feet. And it would be very easy to cross to the hike and bike trail upstream of the bridge. Due to the low water and no flow (at least in part), there’s a lot of scum on the surface around the sample site. Not sure what the rest of the reason is for all the scum.

The flow through the culvert (from the street) is lower than usual, and parts of the water flowing through the culvert are very scummy, as well as somewhat trashy.

The surface algae has reappeared… and much of it near the edge of the stream is dying since the stream has shrunk.

I saw a school of gambusia (minnows) above the waterfall, and we also saw an egret by the sample site. Otherwise, there were no pigeons or other birds, and no other visible aquatic life.

For the first time in memory, the water temperature of 27.5 C (81 F) was slightly higher than the air temp, 26.5 C. No surprise, the dissolved oxygen was much lower – warmer water holds less oxygen than does cool water. Why? per a chemist, in warm water the oxygen molecules have more kinetic energy (they move more) so the gas molecules in hot water can more easily overcome the weak binding forces within water and escape through the surface.

Despite the lack of current that would move microbes, the e-coli count was very low: 16 colonies on a 3 ML  sample.

Observations:
air temp: 26.5 C
water temp: 27.5 C
dissolved oxygen: 3.25
specific conductance 540
pH 7.0
transparency .96 meters
nitrates 0.3

sample site from north bank

trail crossing to sample site

sample site-scummy

scummy water near sample site

trail crossing closeup

low scummy water by trail crossing

trail crossing area

stream from north bank under bridge to trail

downstream view including under bridge

stream under bridge

stream from above culvert

upstream bridge side of water

waterfall closeup

stream from culvert to bridge

closeup of upstream bridge stream side

upstream view from under bridge

stream upstream of bridge from middle of stream

stream with waterfall

stream near waterfall

stream above waterfall

downstream view from waterfall

stream from inlet and upstream

school of gambusia above inlet

downstream view from inlet

low stream with sometime island rocks

sometime island dry

dissolved oxygen 3.25

culvert scum and trash