We dove the nearside point off the cove at Mansfield Park this morning. Temp was from 59-55. Vis was 5-6 foot from the surface to 35 footish. From 40-70 it dropped to 2-3 feet. Below 70 foot to at least 100 the vis was basically zero. We did see some small fish in the shallow areas towards the end of the dive including a baby catfish.
Lake Travis conditions 1/10/05
- Thread starter carlislere
- Start date
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That's a neat stratification pattern. Let me see...
1. Surface waters have decent/good vis.= no plankton blooms, wind-mixing or much runoff. Sounds like super-duper diving! (except its butt cold)
2. Dynamic layering zone(s) have poor vis. = beats me... was it soupy green, soupy grey, or overcast up top?
3. Below permanent thermocline has pathetic vis. = heck it's always crummy down there. Chalk it off to dense phytopigments (natural dyes) and fine particulates.
1. Surface waters have decent/good vis.= no plankton blooms, wind-mixing or much runoff. Sounds like super-duper diving! (except its butt cold)
2. Dynamic layering zone(s) have poor vis. = beats me... was it soupy green, soupy grey, or overcast up top?
3. Below permanent thermocline has pathetic vis. = heck it's always crummy down there. Chalk it off to dense phytopigments (natural dyes) and fine particulates.
archman:
Would you please repeat that............. lol
cyklon_300
Contributor
archman:
on this statement...if vis below the permanent thermo is *always* poor, then how would you account for the conservatively estimated 35' visibility in the river channel (~170') off Windy Point last August...
My log notations show vis at depths >100' was frequently >15' during the late summer.
Wow, I have never read a report from that depth. You're hardcore! I don't know enough about the limnology there to make accurate assessments. But if the vis routinely clears up, that would imply another permanent thermocline (or maybe some other pycnocline). If it's seasonal or fluky, there could be an intermittent bottom current. And if the deepest portions are in fact a riverbed, the sediments will differ somewhat from those of the pecan grove. Rockier sediments tend to have reduced particulate entrainment... fewer silts and clays to suspend.cyklon_300:
Also, reporting vis becomes highly problematic at depth. Use of dive lights introduces all sorts of variation. Different wavelengths, lumen output, beam scattering... what a pickle. Secci disks (used horizontally) sure won't work right, and they're much more accurate than a diver's eyeballs. On one of my few dives into the outer pecan grove, I compared my dive log with my buddy's, and his visibility value was much lower than mine. We discussed it, and decided his much punier dive light was the culprit.
OP
I think I need a drink!
Archman has that effect on people!carlislere:
Teknadv3x
Contributor
Cyklon 300 makes a very true observation ......if vis below the permanent thermo is *always* poor, then how would you account for the conservatively estimated 35' visibility in the river channel (~170') off Windy Point at certain times of the year?
Dave
Dave
Answer these questions, and I'll consult my Lake Travis voodoo cards!
1. Is the "riverbed" an actual bottom feature, and if so, what's it depth range. Or what's the depth difference between the edge of the pecan grove and where the riverbed starts.
2. Describe the sediment and structural features of the riverbed. If its rocky, are they heavily silted over. What about preserved tree stumps or other woody vegetation present.
3. Is clearer vis in the riverbed area seasonal, constant, or variable. If intermittent/seasonal, what times of year is it the clearest.
4. Any discernible temperature differences between the pecan grove and the riverbed.
5. Is the clarity change below the pecan grove at a fairly static depth.
6. What type of dive lights are routinely used by the folks who make these reports.
1. Is the "riverbed" an actual bottom feature, and if so, what's it depth range. Or what's the depth difference between the edge of the pecan grove and where the riverbed starts.
2. Describe the sediment and structural features of the riverbed. If its rocky, are they heavily silted over. What about preserved tree stumps or other woody vegetation present.
3. Is clearer vis in the riverbed area seasonal, constant, or variable. If intermittent/seasonal, what times of year is it the clearest.
4. Any discernible temperature differences between the pecan grove and the riverbed.
5. Is the clarity change below the pecan grove at a fairly static depth.
6. What type of dive lights are routinely used by the folks who make these reports.
cyklon_300
Contributor
in Travis is highly variable. Six days after observing 35+' vis, we dove the same site again and it had deteriorated to ~8-10'. The estimate of 35 feet was probably a conservative figure, it was limited by the distance that a 10W HID light beam penetrated, vis may have exceeded that number. I noted virtually no particulate in the water and items in my field of view were in perfect clarity.
The riverbed is, of course, the natural feature that held the Colorado River prior to inundation by the creation of Mansfield dam. The bed is heavily silted, the actual composition is unknown to me as great care is used to not make contact with it. I have, however, inserted my hand/arm to extract 'treasure' and did not detect a distinct substrate 18-20" below the top of the silt layer.
Temps were 52-54F at >160'.
Using absolutes such as 'always/never' to describe dynamic systems will usually turn out to be erroneous.
The riverbed is, of course, the natural feature that held the Colorado River prior to inundation by the creation of Mansfield dam. The bed is heavily silted, the actual composition is unknown to me as great care is used to not make contact with it. I have, however, inserted my hand/arm to extract 'treasure' and did not detect a distinct substrate 18-20" below the top of the silt layer.
Temps were 52-54F at >160'.
Using absolutes such as 'always/never' to describe dynamic systems will usually turn out to be erroneous.
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