Machinery Weir at the junction of Rivière du Sud with the Saint Lawrence River in Montmagny

**RICHARD L.** · **3 Likes**

Today was a beautiful Spring day and I took a drive to Montmagny, on the South Shore of the Saint Lawrence. Spring discharge of Rivière du Sud was quite remarkable, due to a rapid snowmelt.

I estimated the rate of discharge "Q" at about 1800 cubic feet per second (using the "WEIR EQUATION" Q = CLH*1,5, with C = 3, L = 200 feet and H = 2 feet).

Pentax K3 III + HD DA 16-85 mm ED @ f/11 and 38 mm FL.

**MikeNArk** · 05-05-2023, 05:22 PM

This shot has excellent detail across the image and great colors. That water is really churning over the weir and through the rocks. It would be nice to capture all that energy. Excellent shot.

**RICHARD L.** · 05-06-2023, 07:43 AM

THX !

If you consider that water weighs 62.4 pounds per cubic foot and that the height of fall is about 20 feet, then the river develops approximately :

POWER = 1800 cfs X 62.4 lb/cu. ft. X 20 ft / 550 lb-ft/sec = 4000 H.P. This is the raw power developped by the water discharge over this weir.

Regards

**angkymac** · 05-06-2023, 10:22 PM

I understand your engineering, however I have no reference point from my own background (logging systems) so it remains merely numbers for me.
Yet the shot is amazing simply for the crashing water noise that I can hear through the image!
Angky

**RICHARD L.** · 05-07-2023, 08:29 AM

THX !

The way the site is configured, the power can't be exploited as no turbine could be installed and operated there. Nonetheless the rocky outcrops serve to dissipate this energy as otherwise it would cause scouring and erosion of the bed.

Regards

RICHARD L.
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05-05-2023, 05:22 PM	#2
MikeNArk Loyal Site Supporter Join Date: Sep 2019 Location: Conway, Arkansas Posts: 15,103	This shot has excellent detail across the image and great colors. That water is really churning over the weir and through the rocks. It would be nice to capture all that energy. Excellent shot.

05-06-2023, 07:43 AM	#3
RICHARD L. Loyal Site Supporter Join Date: Oct 2018 Location: Quebec City, Quebec Posts: 6,575 Original Poster	THX ! If you consider that water weighs 62.4 pounds per cubic foot and that the height of fall is about 20 feet, then the river develops approximately : POWER = 1800 cfs X 62.4 lb/cu. ft. X 20 ft / 550 lb-ft/sec = 4000 H.P. This is the raw power developped by the water discharge over this weir. Regards

05-06-2023, 10:22 PM	#4
angkymac Loyal Site Supporter Join Date: Nov 2019 Photos: Albums Posts: 8,962	I understand your engineering, however I have no reference point from my own background (logging systems) so it remains merely numbers for me. Yet the shot is amazing simply for the crashing water noise that I can hear through the image! Angky

05-07-2023, 08:29 AM	#5
RICHARD L. Loyal Site Supporter Join Date: Oct 2018 Location: Quebec City, Quebec Posts: 6,575 Original Poster	THX ! The way the site is configured, the power can't be exploited as no turbine could be installed and operated there. Nonetheless the rocky outcrops serve to dissipate this energy as otherwise it would cause scouring and erosion of the bed. Regards

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