Would it be possible to use a siphon to bring water from the Pacific Ocean to Death Valley? If so how many gallons per minute would a 3" internal diameter pipe supply?
I don’t think this siphon is practical or advisable. I’m just wondering if it is possible.
In a similar vein there has been talk in Israel of piping sea water into the Dead Sea,
and in Egypt of piping water into the Qattara Depression.
I think a Death Valley project might be more topographically challenging, with much
higher moutain ranges in the way.
It’s not going to work. The maximum height you can siphon water up is about 34 feet (more or less depending on the atmospheric pressure at the time).
You’re going to need some pumps.
According to this map, the lowest elevation between the Pacific and Death Valley is at least 1,000 feet, which precludes using a siphon because you can’t lift water more than 34 feet at sea level; the problem isn’t so much air pressure (the lower end of the siphon will pull up on the higher end), but the vapor pressure of water, which will boil when the pressure falls below this point; even freezing water will boil at 4.5 mmHg pressure (thus, you are actually limited to less than 34 feet; a hot day will bring that down by several feet).
Might have better luck tapping lake Mead (+1100 feet) and a hell of a lot closer.
That might still be impossible with a siphon; the elevation map I linked too doesn’t have good vertical resolution but I can easily see rises in excess of 34 feet along the way, unless you followed the same elevation contour as Lake Mead (south from Lake Mead, then northwest to Death Valley, but it looks like it may be too high at a point south of Death Valley).
Also, I forgot to mention in my last post, the lowest elevation route from Death Valley is south to the Gulf of California (part of the Pacific), so the route is much longer than it appears (it would probably be more practical than over the 2-5,000 foot (minimum) mountains to the west if you wanted to pump the water up).
As long as we’re building siphons hundreds of miles long, we might as well solve the elevation problems by digging a tunnel.
You would still be getting downhill flow, if we start at 1100 feet go down 1000 feet and back up 900 feet you will still have water flowing at the top of that rise, as long as you never went over 1100 feet you would be golden.
While this is true for priming the siphon, once primed (water is continuos in the pipe), it is not true for maintaining the siphon and you can go quite a bit higher. The water’s ability not to ‘tear’ apart is much stronger and the water flowing through such a siphon would be under negative pressure.
Once a certain high is exceded however the water will cavatate (basically rip it self apart), a low pressure vacuum/water vapor bubble will form and grow till the water drops back to the 34 foot mark.
In theory, I believe this is correct, although the tensile strength of water is dependent on the intramolecular forces, which I think are pretty weak - probably not nearly strong enough to enable a siphon as described by the OP, crossing a mountain range with a 100ft+ elevation.
In practice, any such real-world setup would just fail almost immediately - because the smallest bubble, foreign body or pressure gradient(say, caused by turbulent flow, etc) would act as a seed for cavitation.
The “Red to Dead” project in Jordan is using pipe considerably larger than 3" and lots of lift stations (pumps).
Horizontal drilling of a pipeline would probably work better.