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How long a dam lasts and how long the reservoir behind it is usable are two different things. A well constructed dam may last 100+ years but if the water flowin

How long a dam lasts and how long the reservoir behind it is usable are two different things. A well constructed dam may last 100+ years but if the water flowing into the lake carries heavy sediment loads, the lake will fill up with mud before then if not periodically drained and the muck removed. This is definitely an issue with Three Gorges as well as Lake Powell/Glen Canyon Dam on the Colorado River. In fact, one of the reasons the latter dam was constructed was to act as a catch basin so the downstream Lake Mead behind Hoover dam wouldn't fill so quickly.

Retric 11y ago
Dredging can solve that problem, it's just a question of what is considered reasonable maintenance.
WildUtah 11y ago
Sediment loads aren't really a problem. The sediment drops out as soon as the water goes slack so it all accumulates at the far upstream section of the reservoir and raises the river level rather than filling in much capacity. The Grand Canyon is filling in with Hoover Dam sediment while the reservoir remains unfilled. In fact, the Grand Canyon is now a mud lagoon starting above Separation Canyon and the water below Pearce Ferry has very little sediment. The upstream sediment slackwater continues to migrate upcanyon, not downcanyon. On Glen Canyon, the sediment accumulated 40 meters deep over Hite but did not slip downcanyon. Instead, Cataract Canyon continues to fill in upstream. Moab will be covered in Glen Canyon's reservoir before any serious capacity is lost because sedimentation moves upriver, just as in any ocean delta. The same effect has stopped the main flow in the San Juan and covered all the rapids up to Slickhorn and even above. --- Above I said, "sediment loads aren't really a problem." I mean they aren't a problem for dam operators. They're bad for the environment, of course. But that should be obvious. For all the selling of hydroelectric as green and sustainable, we should know that it's the most destructive and damaging of all electric generation technologies. Even a failed nuclear plant in full meltdown isn't as destructive and harmful as a properly operating hydroelectric dam. Hoover dam makes Tchernobyl look good.

Retric 11y ago

Dredging can solve that problem, it's just a question of what is considered reasonable maintenance.

WildUtah 11y ago

Sediment loads aren't really a problem. The sediment drops out as soon as the water goes slack so it all accumulates at the far upstream section of the reservoir and raises the river level rather than filling in much capacity. The Grand Canyon is filling in with Hoover Dam sediment while the reservoir remains unfilled. In fact, the Grand Canyon is now a mud lagoon starting above Separation Canyon and the water below Pearce Ferry has very little sediment. The upstream sediment slackwater continues to migrate upcanyon, not downcanyon. On Glen Canyon, the sediment accumulated 40 meters deep over Hite but did not slip downcanyon. Instead, Cataract Canyon continues to fill in upstream. Moab will be covered in Glen Canyon's reservoir before any serious capacity is lost because sedimentation moves upriver, just as in any ocean delta. The same effect has stopped the main flow in the San Juan and covered all the rapids up to Slickhorn and even above. --- Above I said, "sediment loads aren't really a problem." I mean they aren't a problem for dam operators. They're bad for the environment, of course. But that should be obvious. For all the selling of hydroelectric as green and sustainable, we should know that it's the most destructive and damaging of all electric generation technologies. Even a failed nuclear plant in full meltdown isn't as destructive and harmful as a properly operating hydroelectric dam. Hoover dam makes Tchernobyl look good.