Vaal River Update

[edd]

Outflow reached 2000 cumecs in 2010, 14 gates open at around 145 cumecs per gate!

I remeber that, had too be the weekend we booked a trip to the vaal, one month in advance. Needless to say we didn't get any fishing done.

[Pappa Roach]

Will these high flows result in plenty fish dying? I assume that the fish find some refuge in the slower sections of the river, not sure.

[Scythe]

The fish don't die because they are washed away, they die because of :

1) Influx of untreated sewage/Stormwater
2) Increased TDS in water due to soil and detritus agitated by higher flowrates.
3) Poisons such as ammonia which is swept up into the water from rotting detritus/sh!t on the bottom of the river.
4) Low oxygen conditions due to the increased TDS, combined with increased bacterial activity which consumes oxygen and releases CO2, combined with poisonous byproducts from decomposition.

The problem being that Yellowfish are especially succeptible to dying from low oxygen conditions when compared with other less desireable species (from a fly fishing perspective) such as Carp and Barbel, and what's more is that the larger the fish the higher it's oxygen requirements due to biological processes, therefore when there ARE fish kills, it's the big ones that die.

Combine this with the fact that Yellowfish have a relatively low rate of fecundity due to slow sexual maturing, and then factor in that last year was the first year in about 3 or 4 consecutive years that there were no or low numbers of fish kills in the middle Vaal and then one can understand why the numbers of Smallmouth have seen a drastic decline.

[smallstreams.co.za]

then one can understand why the numbers of Smallmouth have seen a drastic decline.

Understand or accept?

[Gerrit Viljoen]

Wrong platform. They only take advice given on Google+ seriously :-)

People's ignorance always land them in a predicament somewhere along the line.

[Gerrit Viljoen]

In their defence, it hasnt rained like this in march for the last 14 years. You could excuse them for thinking the most rain is over and done.

Thinking the rain is over vs oh fak the level is increasing rapidly by the minute (already knowing the Vaaldam is over 100% full) the outflow should be more than the inflow or at least matching can't be an argument sorry. My uncle in Upington(Orange) haven't noticed a rise in water levels yet what does that tell you? They're going to skrik wakker eventually and release one massive amount of water causing serious harm.

[firephish]

always been this way, they are more "scared" of not having "enough" water in the dry months that causing "some harm" immediately ... so they seem to hold off releasing water until absolutely necessary, rather than preemptively releasing reasonably early (which is a risk if the rains don't then arrive).

[Scythe]

Understand or accept?

Understand, never accept.

The wholescale incompetence of the current administration in managing water resources is already affecting humans, do you really think they give a sh!t about the fish?

[smallstreams.co.za]

Understand, never accept.

The wholescale incompetence of the current administration in managing water resources is already affecting humans, do you really think they give a sh!t about the fish?

I did not mean accept how things are, but accepting why they are. Some people really do not care that much as long as they can catch a few fish. Let's be honest, if everyone (very general statement here) were still catching a lot of large fish in the water in it's current (not the floods, oviaaaas) state, would they really care all that much??

[Scythe]

Well I don't understand the question there. We've always known the Vaal is dirty, but at levels 10 years ago, it actually served to increase the total Biomass in the river.

The way we know a system is in trouble (the most apparent reasons at least) is a decline in the indicator species and waterborne diseases affecting humans.

To me the decline in the fishing is merely a symptom of a much greater underlying problem and we (especially the people in Gauteng) should care about the Vaal and it's related systems, where do you think Gauteng gets it's drinking water from?