8/12/2019 L6 Salt Water Intrusion http://slidepdf.com/reader/full/l6-salt-water-intrusion 1/12 4/1/0 1 Seawater Intrusion & Submarine Groundwater Discharge • Today – Submarine Groundwater Discharge – Seawater Intrusion 2 Historic observations 3,000 years ago, off Ruad, Syria, the Phoenicians had built a submarine GW collection system that supplied fresh water to the City of Amrit. Now proposed off Jeddah: Time to Tap Submarine Fresh Water Springs by Essam Al-Ghalib A rab News July 11, 2004 Project SubGATE CH 4 cit.: L. Sonrel (1868) Le Fond de la Mer Courtesy of P. Swarzenski and W. Burnett, USGS
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Pliny, the Elder:… from “Natural History,” written prior to 79 A.D.
“... Black Sea : ~37 miles fromland… springs of fresh waterbubbling out as if from pipes onthe seashore...”
“In fact fresh water may bedrawn from the sea in a great
many places, as at the SwallowIslands and at Aradus [ Syria ]and in the Gulf of Cadiz[Spain].”
More observations …
NYMPHEA WATER
Courtesy of P. Swarzenski and W. Burnett, USGS
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Submarine Groundwater Discharge
Submarine Groundwater Discharge (SGD) =any flow out across the seabed of the continental shelf,regardless of composition or driving force.So, SGD is not defined solely on basis of components, origin, or driving forces.
Courtesy of P. Swarzenski and W. Burnett, USGS
SGD is a ubiquitous, often distributed discharge source along the coastline.
In some areas, such as karst and fractured areas , it becomes a focuseddischarge, often with high discharge rates.
For our simple model, to find intrusion length, L, solvethe flow problem:
At the toe: x= 0, z=b.
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for a confined aquifer of thickness b, & top at depth d .
Simple sharp-interface conceptual model
Q’ = freshwater discharge to sea [L 2/T] z - d = thickness of freshwater h f = freshwater head (above MSL) b = aquifer thickness = thickness of d = depth to top of the aquifer freshwater above wedge “toe”
z = depth to interface (below MSL) L = length of “sea water intrusion”