59 replies to this topic

[AllseeingEye]

Wouldn’t the flow get bigger as the river flows towards the mouth? Ie, the biggest flow is typically where it ends, not closer to the source.

 

The overal water volume would but not the flow; water flow & velocity is decreased by friction along the river bed, so it is slowest at the bottom and river banks/edges - and the further it gets from the river source, i.e. Cowichan Lk - and fastest near the surface and in the middle. The velocity below the surface is typically slightly higher than right at the surface because of friction between the water and the air. More volume results closer to the estuary because the river bed/basin gradually widens and flattens as it approaches the bay allowing for that increased volume. Further up the river are where the deeper sections and pools are, Sandy Pool being one of those. Less volume - but more flow as the river is squeezed into those deeper and narrower sections which also decrease in elevation frrom the source more sharply than does the river further down as it gets closer to the bay. Hence the river becomes more "lazy" than further up towards Riverbottom for example.

[Mike K.]

Ok, it’s semantics, but what I mean is if the river is usually quite low near the bay, it figures it would be quite low at the source.

We can’t expect rivers to be gushing in dry months. It has never worked that way.

[Victoria Watcher]

Presumably in the thousands of years the river existed before the weir the river often ran dry. And sometimes ran raging.

Nothing wrong with us controlling it now, but no reason to pretend we are setting it to a standard nature approves.

[Mike K.]

It’s like that all over the Island. We don’t have Gary Oak groves for no reason, we have a very dry summer climate.

[Sparky]

I am having trouble coping with an increase in height of 70 cm for the new weir but they swear they are not going to raise the level of the lake.

[Victoria Watcher]

I am having trouble coping with an increase in height of 70 cm for the new weir but they swear they are not going to raise the level of the lake.

 

Maybe they have no plans to increase the maximum lake height?  But this lets them keep it higher all season. 

 

 

 

A weir at Cowichan Lake stores water so that it is available for users downstream.  Catalyst withdraws water from the Cowichan River for delivery to the Pulp and Paper Mill and the community of Crofton. Water is withdrawn about a kilometer upstream of the Allenby Road bridge in Duncan. Cowichan Lake is also the water supply for the Town of Lake Cowichan which withdraws water directly from the Lake. The Cowichan Lake level graph below shows the change in lake level over the course of 2023 (black line). the graph is updated as needed.

 

The lake can store water above the crest of the weir, however water stored above the weir is not released into the river at a controlled rate and so it is not considered “available storage”. Prior to July 1, the target water storage is the crest of the weir. After July 1, the target for water storage is a regulated rule curve. For Cowichan Lake, the rule curve is the regulated limit set by the Province for the maximum amount of water that can be stored during the Summer and early Fall.

 

 

 

 

https://cvrdnewnorma...han-lake-graph/

 

 

^ So the pink line is the weir crest.  162.4 maybe.  And it looks like at the start of each year it is as much as 1.1 or 1.2m higher than that.

Edited by Victoria Watcher, 23 March 2024 - 09:32 AM.

[Victoria Watcher]

“This weir will store more water while not raising the natural high water levels of Cowichan Lake.

 

https://www.cheknews...n-weir-1196384/

 

 

I think that means they just keep it higher, longer each season.  So they do not run out whenever they did last year (mid-September).

Edited by Victoria Watcher, 23 March 2024 - 09:37 AM.

[Sparky]

Thanks but I am clearly missing something.

 

The current weir has a particular height where any excess in lake water above that level in my mind would go over the top of the weir and into the river. If they hold back some of that water the lake level would rise. No?

 

I can see where a more automated weir could manage the water better, but why do they need to raise it by 70 cm if they are not going to raise the level of the lake? 

[Victoria Watcher]

One piece above says that they can currently hold the water over the weir level, but can’t control it. Or something.



> The lake can store water above the crest of the weir, however water stored above the weir is not released into the river at a controlled rate and so it is not considered “available storage”.

Edited by Victoria Watcher, 23 March 2024 - 10:30 AM.

[Victoria Watcher]

So maybe the new weir controls right up to the toppy top top.

Edited by Victoria Watcher, 23 March 2024 - 10:31 AM.

[Sparky]

^^ That doesn’t make any sense unless the lake water has a hill.

[Victoria Watcher]

You think the engineers made a huge mistake?

Maybe write the ministry.

[Victoria Watcher]

Maybe they never let the current water reach the weir crest or it gets too funky. New weir they can.

I’m trying to work with you here, bro.

Edited by Victoria Watcher, 23 March 2024 - 10:36 AM.

[Sparky]

Bless you. I’ll get back to you tomorrow after I have been there and see it for myself. Standby for my report.

I have learned over the years to always be cautious when it comes to politicians funding projects that have anything to do with water.

[Nparker]

...I have learned over the years to always be cautious when it comes to politicians funding projects that have anything to do with water.

This is all that one needs to say.

[Victoria Watcher]

Bless you. I’ll get back to you tomorrow after I have been there and see it for myself. Standby for my report.

.

Sparky Goes To The Weir is the hottest opening act for the Tinto Rocks Fest since Franky Goes To Hollywood in 1988.

[Sparky]

Sparky peeing off the weir could go viral on YouTube.

[max.bravo]

Makes sense to me. The weir won’t raise the “natural” high water level of the lake. So they will raise the weir from its current level, but that’s still below the natural high water level or the lake.

As opposed to a weir that’s higher than the natural high water level; like a dam that’s designed to flood the surrounding valley.

[Nparker]

What is the difference between a weir and a dam? A weir generally allows the water to flow over the crest (which is the top) or sometimes underneath some sections. In comparison, dams mainly allow water flow to be regulated (controlled) by gates or spillways. A dam usually does not allow water to go over the crest.

https://www.waternsw...-is-a-Weir-.pdf

 

[Victoria Watcher]

True. But lots of dams have adjacent spillways in case of extreme situations or malfunctions.


The Oroville dam crisis was something:

https://en.m.wikiped...ille_Dam_crisis

Edited by Victoria Watcher, 23 March 2024 - 12:23 PM.