Tuesday, July 11, 2006

Flow rates update

hi guys,

Online flow rate data is not accurate at the moment:
The Rand Water site is out of date http://www.randwater.co.za/Education/Edu_Details.asp?ArticleId=48
and the DWAF site is registering erroneous flows at the Goose Bay sensor and no data for the Schoemansdrif sensor http://www.dwaf.gov.za/Hydrology/rtmain.aspx

In winter it is generally safe to take a flow rate reading from the next sensor upstream which in this case is the Vaal outflow sensor currently reading 12m^3/s and add a few tons for water entering at the barrage to arrive at an estimated flow of between 15 and 20 m^3/s.

hope this helps,

Sunday, July 09, 2006

Middle Vaal Report July 2006

Once again I am getting this report out later than I should have; sorry about that…

I was on the river today, the barometer was climbing all of last night, the weather was nice and stable, the wind was a very light occasional West North Westerly: The conditions were better than they have been in months.

I didn’t catch anything.

I saw a few nice largies moving in a little bay I was exploring for the first time. One of my anchors was lost to a sunken tree; I got a flat tyre while making my way back to the dirt track that leads off of the farm: It was an eventful day I suppose, as mid winter days go when the river is in deep slumber. Frankly I didn’t make too much of an effort to wake her, I just enjoyed the calm weather and spent my time slowly moving over a kilometre or so of river looking for active fish, made a few casts, lifted a few rocks, took a few photographs… pretty much remained in “standby mode” in case the river woke up… it didn’t wake up.


This has been a seriously cold winter, the coldest in a good few years, my Clivia at home have been hammered by frost; but then they are right next to the stream so I shouldn’t be surprised.

We’ve had a steady stream of cold fronts over the past 4 or 5 weeks, although none as bad as that whopper in June. Water temperatures are hovering between 9 and 13 degrees, which is not unusual for winter…the fish are cool with that.

Flow rates are pretty steady now at around 15 with occasional blips to 20 or 25 and troughs to 10. Remember the Vaal used to stop flowing in winter so the ecosystem is evolved to handle no flow in winter. The winter flows we experience are due mainly to discharge from industrial, residential and agricultural use.

Water quality is a little “off” at the moment but may not be as a result of human activity. I recall the same conditions after the floods in the late 90’s: high levels of diatoms, tea coloured water, a white foam on the surface downstream of broken water. Hopefully these are all a result of the river rebalancing after the floods and not from pollution. I’ve spoken to the parties responsible for monitoring water quality along the middle Vaal and no report any new pollution.


Caddis are all but non existent now as we move through mid winter, the mayfly are starting to pick up although pretty slowly. There were a few #14/15 dirty brown duns on the water around mid day today, not a lot, probably a 2 or 3 out of 10 score for density, but I still have hope we’ll see some dense hatches later in winter. There are a lot of small nymphs under the rocks that should mature and emerge in a month or 2: Hopefully that will coincide with some stable weather and the dense emergence will bring the fish on.

Blackfly larvae and pupae are about in large volumes (as always) and a few vacuum lines on the rocks today confirmed that the fish are feeding on this ever-present staple.


I am not going to regurgitate last month’s content here, suffice to say that the same advice certainly still applies and can be found here: http://www.yellowsonfly.com/uploads/Middle_Vaal_update_june_2006.pdf.

I came across a great article on swinging flies, this is a very effective approach year round on the Vaal, check it out here: http://www.midcurrent.com/articles/techniques/likakis_beyondtheswing.aspx

Large and smallmouth are being caught, not in great numbers and not everyone is being rewarded for their hours of hard work on the water, but the fish are coming to the fly.

This is a beautiful time of the year to be on the river, even if the fishing is patchy you should treat yourself to some quite time on the Vaal in the next few weeks, even if just to reflect on the spring fishing which is only 8 weeks away. Today I watched 3 woodpeckers (couldn’t make out species) working in amongst a grove of pecans while I waited for fish to move.

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Look after the river,