In reading about New Orleans, it has become apparent that all of the centuries work in damming and straightening the Mississippi River has had serious consequences for New Orleans, and coastal Louisiana. The delta is now being washed away, because the river now deposits its sediments in deep waters, instead of replenishing the delta lands.
In the case of Egypt, the Aswan Dam has had serious effects:
-Egyptian farmers no longer get the enrichment of their fields from the annual Nile floods-they now must buy fertilizer
-the Nile Delta is being washed away
-Lake Nasser is silting up-it will have to be dredged to maintain the power production
-the ecology of the river has changed (less fish due to lower nutrients)
Has anyone ever calculated how much damage to the Egyptian economy was caused by the dam? The Dam has provided benefits (electric power), but was it worth the ultimate cost?
Correction: a dam deprives a delta of its regular “supply” of upstream sediments to, well, maintain the delta. Without that, the sea will reclaim the delta area for itself.
Another consideration I read about. All water is marginally salty. If you spread water and it evaporates, you get salt deposits. the Egyptians eventually figured out they had to over-water, so the salt buildup would wash away.
They are trying to divert the excess water in Lake Nasser to a second depression to the west of the Nile to create a new agricultural area - very apparent in google Earth. This was a grand idea, but the practice is proving much tougher.
A lot of the ecological damage claims may be sour grapes, since the west was miffed that Nasser picked Soviet help to build the dam. However, the silt issue is real; apparently with Three Gorges Dam, the Chinese learned this lesson and I read that they build low-down gates on the dam to help flush some of the sediment.
Much of the original flooding was controlled by the lower dam, built in the early 1900’s by the British.
Egyptian Nubia was utterly destroyed; the people had to be forcibly relocated while their homes (and countless undiscovered artifacts) now lie on the bottom of lake Nasser. At least Abu Simbel was saved…
Modern farmers don’t like annual floods. They want to control the soil composition, and they like to have things like barns and homes that aren’t destroyed every year. The amount of fertilizer brought by the river is nice for 4,000 years ago, but it’s not sufficient for modern agriculture.
As for the rest: I don’t think anyone in the world can put serious numbers on that. Fish can be imported. Silt can be dredged. Deltas are hard to put a value on - the people who tried in New Orleans came up with something that very few people consider a real value.
Compare that to electricity generated (carbon-neutral power nonetheless!) and lives and property saved and I don’t know how you can call the Aswan dam a net cost.
One of the quickest comparisons is to look at the effects of Hurricane Camille and Hurricane Katrina. Both of them hit in about the same place. However, Camille was a Cat 5 storm when it hit, and Katrina was only a Cat 3 when it hit.
The difference is that Camille hit in 1969 and Katrina hit in 2005. During that time, New Orleans has effectively moved nearly 50 miles closer to the Gulf because of the loss of the marshlands barriers. As a result, Katrina hit a lot harder in net effect.
Louisiana loses about 34 square miles a year and has done so for the last 50 years.
Actually, several sites were saved; or moved, the Met in NYC has a complete small Egyptian temple that would have otherwise been flooded. Philae Temple was moved near Aswan, but it was flooded by the 1900’s British dam.
Yes, Aswan is quite large (over a million people I think) and a lot came from the displaced peoples; and there is significant resentment by the Nubian population. OTOH, Egypt as a whole is 80M+ people. I haven’t seen a map of how much arable land was flooded, but the valley was a deep canyon at that point (hence the good location for a dam) so I imagine it was a case of "you can’t make an omlet without drowning a few eggs.
I realize this isn’t GD, but another thing to consider in its ’cost’ is that the Aswan Dam essentially forced Egypt to be the first Arab country to make peace with Israel. Although the dam is heavily defended, in the 1973 Arab-Israeli War Israel on several occasions struck the dam with practice paint bombs as a way of saying, ‘At any time in the future we can destroy this structure and put all of Cairo under 30 feet of water and there’s nothing you can do to prevent it’. This was a major factor in forcing them to the peace table. Which of course directly resulted in Egyptian president Sadat being assassinated.
Overall though, I’d say that forcing peace with Israel was undeniably a good thing, even if few Arab states have followed suit…
One should note though that Katrina was MUCH bigger, which had a big impact on storm surge, which did most of the damage (the weakening before landfall didn’t have much effect since it takes days for the surge to build up and vice-versa, so Katrina effectively brought Cat 5 level storm surge):
I’m dubious about this - the Aswan High Dam is an embankment dam - basically an enormous mound of rammed earth 980 metres wide at its base and 40 metres wide at its crest, rather than a ‘thin-skinned’ gravity or arch-gravity dam (like the Hoover dam for example). What sort of ordinance could the Israelis have used to punch through a 40-980 metre wide earthern berm?. While they might make a small breach near the top there’s no guarantee that would lead to a catastrophic failure. Hell it could probably survive a modest-sized nuclear strike.
This was a topic of discussion in a previous thread here:
http://boards.straightdope.com/sdmb/showthread.php?t=512678&highlight=aswan
And Stranger on a Train made essentially the same point I have in posts #27 and #30 and following. There’s no feasible way for the IAF to do this, short of ground-penetrating nuclear weapons.
From what I’ve read, there’s also the health effects from the dam. Once water from the river slowed down, it because the perfect breeding ground for the Bulinus Water Snail. The growth of this snail increased the rates of Schistosomiasis.
The airport at Aswan is also a military base. You can see the individual aircraft bunkers along the apron and taxiways; so it would take dozens of air strikes just to take care of the protective air force. Of course, this presumes some relative effectiveness of the Egyptian Air Force.
We knew even before Johnstown that all it takes to destroy an earthen dam is to get water flowing over the top of it. That erodes material, which lets more water flow over it, which erodes more material, etc. until the dam isn’t damming anything anymore.
So, just blast a crater in the top of the dam, enough to get below the water level, and wait for a bit.
Maybe but what sort of air-delivered ordinance can blast a creater more than 40 metres across (and tens of metres deep across the 40 metre+ wide crater) through compacted clay? Seriously look at the scale of the thing on this google maps view here. If you zoom in far enough you can see ‘tiny little’ buses parked at the observation point amidst a line of trees.
Even if you could get a little breach near the top the dam won’t erode away particularly quickly, as it’s built on a very shallow angle and the deeper the breach goes the wider the dam quite swiftly, all you’ll achieve with a ‘shallow near-top’ breach is a moderate increase in the Nile’s flow. And the Egyptians could probably open the sluice gates fast enough to drop the level below the breach in fairly short order. Remember the dam is built to accomodate the Nile’s annual floods, so there’s a lot of built in redundancy.
Seriously, if Israel really wanted to kill millions of Egyptians it would a lot easier to just nuke Cairo.
Ps. you can’t compare the relatively tiny South Fork Dam(which caused the Johnstown Flood), built in the late 1800s and with a resevoir holding about 0.02 cubic kilometres with the Aswan High Dam which holds back 132 cubic kilometres.
Your link takes me to New Zealand. Did Egypt offshore the dam?
Told you it was big!
Sorry, my mistake thanks for the correction.
What makes you think Israel doesn’t have these? They are estimated to have at least 300 nuclear warheads, including +1MT city busters, they have reliable & accurate IRBMs to deliver them, and if push really came to shove I have little doubt they’d hesitate to use them if faced with destruction of the Jewish state…