Positive Water Pressure on the Slopes

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Dust
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Joined: Mon Jan 29, 2018 6:49 pm

Positive Water Pressure on the Slopes

Postby Dust » Sat Mar 10, 2018 4:34 pm

I can visualise chains of ponds and how that leads to positive water pressure into the floodplain. What I cannot visualise is achieving the same on the steeper country. Can anyone help?

duane
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Location: Central Coast, NSW
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Re: Positive Water Pressure on the Slopes

Postby duane » Wed Mar 21, 2018 5:38 pm

How are you visualising this in a chain of ponds??

Dust
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Joined: Mon Jan 29, 2018 6:49 pm

Re: Positive Water Pressure on the Slopes

Postby Dust » Wed Mar 21, 2018 8:15 pm

I'm seeing a raised creek bed, with the water in it charging laterally out into the lower surrounding floodplain, that water is effectively "springing" "up" out of the surface of the floodplain.

duane
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Joined: Fri Apr 20, 2007 1:44 pm
Location: Central Coast, NSW
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Re: Positive Water Pressure on the Slopes

Postby duane » Wed Mar 28, 2018 5:11 pm

Well done Dust.

In an old, intact floodplain system, the streams were in the highest part of the system, creating a head of pressure, which pushed water down and laterally, recharging the system (-ve pressure). This in turn, is pushing the water in the floodplain up (+ve pressure) or as you have put it, ""springing" "up" out of the surface of the floodplain". Springs, soaks, swampy meadows are all under the influence of positive (or discharge pressure).
This has tremendous outcomes for plant productivity, specially in native plants and grasses.

In steeper country, where natural or built contours occur, the same recharge/discharge sequence occurs. Remembering, that a contour is a line of equal levels. It is NOT a drain or swale. So imagine you're on a slope, with a newly constructed contour with a bank in front and a channel behind. Water that enters the contour, performs exactly the same as the creek/stream. Water recharges, going down and moving laterally, just like the stream did. Below the contour bank, the water becomes under positive pressure ., it is under positive pressure from the head of water above it. So, now it is discharging, just like in the floodplain. If you can imagine the rice terraces say in Asia coming down the mountain???? Then that's it>

Contours change the landscape hydrology.....

Hope this helps.

Dust
Posts: 9
Joined: Mon Jan 29, 2018 6:49 pm

Re: Positive Water Pressure on the Slopes

Postby Dust » Thu Apr 12, 2018 7:29 pm

Thank you for your reply Duane. I think what helps me visualise all this, is you only have positive water pressure working if the landscape is already full of water? That is, whatever moving out of the contours/raised streams has no choice but to ride (through the ground) above the pre-filled clay/floodplain layer into the topsoil layer.


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