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Old 05-05-2008, 01:25 PM
Status: "60th anniversary of the polio vaccine! Hail to Pitt!" (set 10 days ago)
 
Location: Foot of the Rockies
70,055 posts, read 60,607,466 times
Reputation: 20201

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Quote:
Originally Posted by BrianTH View Post
Yes, because you have access to water from a much bigger drainage basin. Again, you can think of the relevant drainage basin as a big funnel leading down to the developed parts of the region. The mouth of the funnel leading to Denver is much MUCH bigger than the mouth of the funnel leading to Atlanta. So, even with substantially less rainfall per unit of land, Denver ends up getting a much higher volume of water being funneled to it.

Another notable possibility is something like a glacier, with, for example, Boulder getting a substantial amount of water from the Arapaho glacier. But I am not sure if Denver gets any water from glaciers, as opposed to seasonal snow fields.
I actually don't know how much water Boulder gets from the glacier. I think it's more a publicity stunt than anything else. I believe most of it (water) comes from somewhere into the Boulder Reservoir. You can search this site if you want. City of Boulder, Colorado -- Official Web Site - Home Page

Quote:
I'm sure the Army Corps of Engineers did some studies back when they constructed Lake Lanier, which may have included studies of alternative sites. But that was back in the 1950s, so I am not sure those would be available online.

But more broadly, I hope the appropriate question you need to be asking is clear. The question is not whether a reservoir could be built, but rather whether there would be any water to go in that reservoir that is not already being captured by Lake Lanier. And that is fundamentally not an engineering issue, but rather a question for a hydrologist.
Well, fine, then a hydrologist's opinion. I think a key phrase in your post is "back in the 50s". Atlanta is a much larger city now. They need to get on with it and do what they have to do to capture some of their 48"/yr.

Last edited by Katiana; 05-05-2008 at 01:28 PM.. Reason: add link

 
Old 05-05-2008, 01:38 PM
 
20,274 posts, read 18,883,560 times
Reputation: 2827
Quote:
Originally Posted by Katiana View Post
I actually don't know how much water Boulder gets from the glacier.
The only stats I have found lump it in with the Silver Lake Watershed, for a total of 40%.

Quote:
Well, fine, then a hydrologist's opinion. I think a key phrase in your post is "back in the 50s". Atlanta is a much larger city now. They need to get on with it and do what they have to do to capture some of their 48"/yr.
At this point, we seem to be going in circles: you cite rainfall per unit of land statistics, I explain why you also need to look at the size of the relevant drainage areas to calculate the total volume of water, and then you cite the same rainfall statistics again without having addressed the issue of the relative size of the drainage areas.

So, I guess we are done.

Last edited by BrianTH; 05-05-2008 at 01:51 PM..
 
Old 05-05-2008, 02:03 PM
Status: "60th anniversary of the polio vaccine! Hail to Pitt!" (set 10 days ago)
 
Location: Foot of the Rockies
70,055 posts, read 60,607,466 times
Reputation: 20201
Quote:
Originally Posted by BrianTH View Post
The only stats I have found lump it in with the Silver Lake Watershed, for a total of 40%.



At this point, we seem to be going in circles: you cite rainfall per unit of land statistics, I explain why you also need to look at the size of the relevant drainage areas to calculate the total volume of water, and then you cite the same rainfall statistics again without having addressed the issue of the relative size of the drainage areas.

So, I guess we are done.
Well, I think it should be done, too, but I don't see it quite the same way you do. One does not live out here in the west w/o being aware of water issues. I could ask my resident physicist about this drainage thing, but he's not here, he's out designing telephones at the moment. Frankly, I think if you looked at the drainage area of each of these legions of reservoirs that the Denver Water Board has, they are each in and of themselves not all that large.
 
Old 05-05-2008, 02:07 PM
 
20,274 posts, read 18,883,560 times
Reputation: 2827
By the way, I did just come up with one more angle to try to explain the basic problem, so here goes:

The volume unit of measure that water resource people typically use is the "acre-foot". See here:

Acre-foot - Wikipedia, the free encyclopedia

So, how would one go about calculating the number of acre-feet per year a given annual rainfall in inches corresponds to?

The first part is easy: you are starting with inches per year, so you can convert to feet per year by dividing by twelve.

OK, but now how do you get from feet of rainfall per year to acre-feet of rainfall per year?

I hope the answer to that question is somewhat obvious. And once one figures out the answer, I hope the potential problem becomes obvious as well.
 
Old 05-05-2008, 02:15 PM
Status: "60th anniversary of the polio vaccine! Hail to Pitt!" (set 10 days ago)
 
Location: Foot of the Rockies
70,055 posts, read 60,607,466 times
Reputation: 20201
What do you mean obvious? You're looking at the acre feet feeding into one reservoir? My entire contention is they need to build some more reservoirs, on some more streams or rivers. This is not rocket science.
 
Old 05-05-2008, 02:28 PM
 
20,274 posts, read 18,883,560 times
Reputation: 2827
Quote:
Originally Posted by Katiana View Post
Frankly, I think if you looked at the drainage area of each of these legions of reservoirs that the Denver Water Board has, they are each in and of themselves not all that large.
You are looking at two main drainage areas (Boulder Creek is a third, but it is small enough to disregard). The first is the South Platte River drainage area, which is about 24,300 square miles. See here:

USGS Colorado Water Resources--South Platte River Basin

The second is the Upper Colorado River drainage area, which is about 17,800 square miles. See here:

http://co.water.usgs.gov/nawqa/ucol/pdf/ofr94-102.pdf

Again, the Lake Lanier drainage basin is about 1000 square miles, specifically about 1040. See here:

Map Room (http://lanier.sam.usace.army.mil/MapRoom.htm - broken link)

I used that last link because I found some cool maps of the drainage areas in the Southeast there. This one in particular really demonstrates the problem:

http://lanier.sam.usace.army.mil/maps/Watershed_Map_Southeast_USA_11x8.pdf (broken link)

Atlanta's water comes from just that little piece of the yellow area to its north. All the other water in the area is draining away from Atlanta.
 
Old 05-05-2008, 02:35 PM
 
20,274 posts, read 18,883,560 times
Reputation: 2827
Quote:
Originally Posted by Katiana View Post
What do you mean obvious? You're looking at the acre feet feeding into one reservoir?
No, the total amount of acre-feet of water falling in the form of rain on the relevant area. How would you calculate that?

Quote:
My entire contention is they need to build some more reservoirs, on some more streams or rivers. This is not rocket science.
What streams or rivers do you have in mind? Lake Lanier already captures the water from the Chattahoochee and Chestatee Rivers. What else is left?

And you are right, this isn't rocket science, it is hydrology. Which makes it a much harder problem: people can build rockets. People cannot build an entire drainage system.
 
Old 05-05-2008, 02:54 PM
Status: "60th anniversary of the polio vaccine! Hail to Pitt!" (set 10 days ago)
 
Location: Foot of the Rockies
70,055 posts, read 60,607,466 times
Reputation: 20201
Quote:
Originally Posted by BrianTH View Post
No, the total amount of acre-feet of water falling in the form of rain on the relevant area. How would you calculate that?



What streams or rivers do you have in mind? Lake Lanier already captures the water from the Chattahoochee and Chestatee Rivers. What else is left?

And you are right, this isn't rocket science, it is hydrology. Which makes it a much harder problem: people can build rockets. People cannot build an entire drainage system.
Ha, Ha! You are not a hydrologist. I am not a hydrologist. I suggest we end this nonsense.
 
Old 05-08-2008, 04:42 AM
 
Location: Los Angeles Area
3,306 posts, read 1,484,505 times
Reputation: 592
Oh oh, it ended!
 
Old 05-13-2008, 07:46 AM
 
71 posts, read 180,034 times
Reputation: 27
It's 9am here in Pittsburgh and it's sunny. I've lived in the San Francisco Bay Area for close to 25 years (after living in Pittsburgh) and I actually like the weather here. Most mornings in the Bay Area were grey and cool due to the fog which I always hated and found depressing. And the summers are dry. At least here you can have a grey morning but it's actually warm and balmy rather than freezing. I happen to like the rainy days and even enjoy some humidity.
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