July 2010 monitoring

July 10 monitoring: last week Hurricane Alex hit Mexico and the border areas, resulting in significant flooding at the border. Here in Central Texas we just received about 3.25″ of rain over several days. That ended yesterday, don’t expect any more rain today or tomorrow.

Although it’s only 28 C (83 F) degrees, the humidity makes it feel like it’s in the low 90s. Yuk! Anyhow, thanks to the recent rains, the stream is looking MUCH better. The surface algae is gone, and the stream level has risen noticeably. Unlike last month, the waterfall is running pretty strongly, the trail crossing rocks next to the sample site are covered, and in general the stream is noticeably wider upstream of the bridge and under the bridge.

We saw a few minnows upstream – not too many, but given the fairly fast current, I guess that’s not surprising. And a very observant 8 year old visitor pointed out several caches of frogs eggs above the waterfall (see the photos). Hope they hatch before the stream shrinks and they are  exposed.

Other observations:

• at 7.0 average, the dissolved oxygen is doing well for the water temp of 26 C (80 F).  There’s no comparison from last year (August 2009); at the height of the drought and heat the DO was barely 0.5.
• the sample site pool still has a bit of “litter” on the surface, which is probably pollen etc from the overhanging trees (see photo), but not near as much as during the last visit.
• the pH is also holding steady at between 7.0 and 7.5, and the nitrates are normal – a good sign.

The e-coli readings are still high, but given the recent rains that’s not surprising, since the chemicals and bacteria residue of car washing, other human activities and pet waste end up in the creek via the storm drain and general runoff, including from the bridge (see the photo of the openings in the bridge wall).

To calculate the e-coli colonies, we again used 1 ML water samples and multiplied the counts by the dilution factor of 100. The resulting counts are:

• above the drain: 1100 colonies (last time was 750)
• at storm drain: 1900 colonies (last time was 1450)
• by the usual sample site: 900 colonies (last time was >6000)

When the two upstream counts increased, why was the usual sample site, which is downstream of the other two, lower? My only guess is the current is faster there so the bacteria don’t remain in that location as long. Maybe the LCRA experts have some ideas.

view of sample site from above

some surface debris at sample site

view of stream, trail crossing rocks & sample site from under bridge

closer view of the trail crossing rocks and sample site

the trail crossing rocks & the south bank – a park with lush greenery after all the recent rain

a view of the south bank next to the bridge – a good place to watch for erosion after future heavy rains

trail crossing & bridge from upper south bank

another view of the stream and bank under the bridge

some flowers between sample site & bridge

stream under the bridge & the south erosion bank

water under the bridge covers where we worked last month

water from recent runoff from the bridge remains under the bridge

the runoff comes from the drains in the wall under the bridge (with its latest graffiti)

view upstream from under the bridge

near the storm drain there is some surface algae but not near as much as last month

water entering stream from the storm drain

another view of water entering the stream from the storm drain

above the storm drain there is some new debris near the traffic cone

the waterfall is back!

looking downstream from above waterfall

another view of looking downstream towards the bridge

looking upstream from the waterfall

a view of upstream from a bit farther upstream from the waterfall

underwater algae just above the waterfall

much more water than last month roughly 100-150 ft above the waterfall

and also many clumps of underwater algae – but none on the surface

a clump of frogs eggs

dissolved oxygen is still 7.0

pH is normal, between 7.0 and 7.5