Lanier should stay above 1035 feet until sometime next summer
A few days ago we once again tried to compute how many days worth of water were left in Lake Lanier, based on the new information that the flow through Buford Dam would be cut by 16% in a few weeks.
The date we first arrived at was August 9, 2008. However, this didn’t account for evaporation — a potentially significant number. A helpful reader (thanks Ben!) ran some numbers and felt that 25 million gallons/day was a reasonable estimate. It’s very hard to get a specific number, as evaporation rates can vary based on temperature, humidity, sunlight, wind speed, etc. 25M gallons/day was felt to be a pretty good number.
Today I received a PDF from the River Basin Center at UGA (courtesy of Thomas Wheatley at the Creative Loafing: Fresh Loaf blog). Part of the PDF talks about the increased rate of evaporation in the Lanier area after the lake was created. It reads, in part:
…water loss from the system following construction of the reservoir increased by roughly 33 percent, which represents 28.3 million gallons per day or water supply for approximately 170,000 Atlantans.
This is remarkably close to the estimate that Ben had provided. Given that the rate of evaporation will decrease as the lake gets lower, but then increase as summer begins leads me to think that an average of about 25M gallons/day is still pretty good.
This puts our new official guess at July 31, 2008. At that point we’d still have “dead pool” water available, but the main supply will be exhausted. There are literally hundreds of other factors that should be computed in there (other municipalities that take water out, rain coming in, etc), but no one else has been willing to make a guess with the new numbers so we thought we’d give it a shot.
Given some of the scary estimates a few weeks ago, this seems to be good news. We’ll just have to keep a close eye on it and see what happens.
November 5th, 2007 at 2:21 pm
I think this can be simplified -
I took the data from 10/1 through 11/5 and got an average loss of (0.10444) feet per day.
Given we do nothing, the 20.19 remaining feet will run out in 193 days, on 5/16/2008.
Given the estimated 0.02 drop in loss if the flow is reduced, that gives an average loss of (0.08444) and 239 days - 7/01/2008.
If the loss per day grows because the lake is concave, that would only speed up the process, all other things being equal, wouldn’t it?
I’m putting my money on a date between 5/16/2008 and 7/1/2008.
November 5th, 2007 at 2:28 pm
Keep in mind that we got about 1.14 inches of rain during that span. We’ll need that much rain each month to make those numbers stay consistent.
You are correct that the natural shape of the lake will speed up the process — that’s what all of my cone math was trying to resolve. Of course, as the lake gets smaller it’ll lose less each day to evaporation as well (though not enough to offset the increased loss due to the narrower lake).
Every day is putting us one day closer and putting a little more data behind us to use. In a month or two we should be able to refine the guesses much further.
November 5th, 2007 at 2:37 pm
That’s true. Hm. I knew it seemed too easy.
November 5th, 2007 at 2:52 pm
You never know — your theory is pretty solid, it just approaches it from a different direction. I’m feeling like my July 31 guess is too far out, but that’s what my numbers are saying. I think yours might be closer to the truth.
It’s so hard to know for sure…
November 5th, 2007 at 5:00 pm
Look at AJC-published data and a calendar, and it’s simple math. We will be out of clean water by January 31. As of 11/1, the state said we had an 80-day supply and were releasing 3.2 billion gallons a day. Add 350 million for 5 million people @ 70 gallons per day, and the depletion rate is 3.55 billion gallons a day. The 80-day supply would be a 284 billion gallon reserve, and we’d be down to 231 billion by 11/15, then deplete at “only” 3.05 billion gallons a day. 231/3.05 = 76 days from November 16. The 16% reduction would save us 11 days.
November 5th, 2007 at 9:10 pm
Where did the 3.2 billion number come from? Most days, it only loses about 800 million gallons. Also, you can’t add Atlanta usage numbers to it, as Atlanta’s main intake is south of the dam — we take a chunk of what is released through Buford Dam after it’s gone downstream for a little while.
Today has been worse than normal (I’m not sure why), and it’s only going to be a loss of about 929 million gallons (1,435 CFS):
http://www.tinymicros.com/cgi-bin/nph-lake.pl
Also, you can look at the USGS stats for reservoir storage. Most days see a loss of between 2000-3000 acre feet of water. 3000 acre feet = 979M gallons.
Do you have a link for the 3.2B gallons/day from the AJC?
November 6th, 2007 at 9:28 am
Wow check out the new numbers http://www.tinymicros.com/cgi-bin/nph-lake.pl ! A loss of 2,017,801,300 gallons and a drop of 2.4 inches in just one day is the worst that I’ve seen so far. And looks like tomorrow we should reach and pass the next record low set back in 1986.
November 6th, 2007 at 9:39 am
I asked that in the forum - 1.83 billion gallons of that is outflow from the dam itself - that’s double-normal. What gives?
November 7th, 2007 at 4:15 pm
The 3.2 billion gallons number came from 10/25 article “Allow only unimpaired flows from Lake Lanier,” which also states that that is the release at the Georgia-Florida state line, and it was written by the Commissioner of the city of Atlanta’s Department of Watershed Management. On 11/2, the article “States to End River Rivalry” again refers to the 3.2 billion being cut to 2.7 billion. On 11/1, the article “Water Wars Land in Washington’s Lap” refers to the 80 days supply (the corps estimates it higher) and it also refers to the 70 gallons of water per day per person.
November 7th, 2007 at 4:27 pm
Thanks for the info. I think I see the confusion.
3.2B gallons at the state line is much different than 3.2 gallons out of the dam. Other water sources feed into the river while it’s in Georgia, helping to raise that number. The billion or so gallons that is released daily from Lanier is a starting point, and it climbs to 3.2B by the time it hits the state line, after being fed from other smaller creeks and rivers.
I think.
November 7th, 2007 at 4:57 pm
I just read the river rivalry article again, and it does say that about a third of the 3.2 gallons is provided by Lanier. So you may be right. I’m not an engineer. Still, if they were saying an 80-day supply as of 11/1,that sounds pretty bad. I guess I’d better buy more water filter cartridges in case they have to start drawing from “below the readily-available level” early next year and the water’s quality deteriorates significantly. I did look up the links for you:
http://www.ajc.com/search/content/governors1102b.html
http://www.ajc.com/search/content/governors1101b.html
http://www.ajc.com/search/content/opinion/stories/2007/10/24/huntered_1025.html
I see that the Centennial Park skating rink is having water trucked in from Kentucky and it’s going to cost them the equivalent of 31 cents a gallon. If we all had to pay $310 per thousand gallons, for a mere 2,000 gallons a month, that would be $620 a month for household water. I think I’d move.
November 7th, 2007 at 5:08 pm
Not only that, but the general rule is 70 gallons per PERSON. We’re a family of four, so that’d be about 8000 gallons/month, or about $2480/month for water.
We’re a bit below that number of gallons, but not much.
November 9th, 2007 at 4:01 pm
The days to depletion calculation can be simplified.
The State said on 11/1 that we had an 80-day supply. So on 11/16, we would have a 65-day supply. A 16% reduction then would mean usage at 84% of whatever the rate has been. So just divide the # of days supply by 1 minus the reduced percent (or the increased percent if applicable, since today’s AJC said it’s increasing from 1.2B to 1.7B gallons a day–a 42% increase).
D = days left as of 11/16/07
D = 65/(1.00-0.16) = 65/0.84 = 77 days (11 weeks–1/31/08)
D = 65/1.00+.042) = 65/1.42 = 46 days (Happy New Year)
If we believe the Corps of Engineers instead, they said on 10/19 that we had 282 days minus 169 below the normal usable pool, for a total of 113 days. So on 11/16, 28 days later, there would be 85 days.
D = 85/.084 = 101 days (2/25/08)
D = 85/1.42 = 60 days (Mid-January)
It seems fairly certain we will have a water quality problem soon if we have to draw from deeper down, and the sediment may clog pipes. Can’t we just send Alabama and Florida electricity instead of water and let God decide if it’s time for the mussels to die out?
November 10th, 2007 at 12:28 pm
lanier is NOT the issue - focus on the problem - a reliable water source.
November 10th, 2007 at 1:21 pm
Long-term, yes, you are correct — we need a reliable water source.
For now, though, there is no other water source. It’s Lanier or bust.
November 10th, 2007 at 1:29 pm
We have 3 months to do something in addition to Sonny’s (?) prayers…
There may not be solutions to the Lanier problem but there are alternative solutions to the PROBLEM. The problem is not Lake Lanier, the problem is a reliable water source. Possible solutions: Wells; Pipeline from Great Lakes; Desalinization, etc. The Lake is gone and may never recover if releases continue. So, solutions are needed for the problem and not Lanier. And, prayer vigils are not going to re-fill the lake. We only have a couple months to get meaningful actions in place and those with the resources and power and budgets are praying and not planning!!!!!!!! People need to stop focusing on rain and Lake Lanier - the world is 80% water, it’s time to get creative. Water is not the issue, creativity is what’s lacking.
November 12th, 2007 at 4:09 pm
Prayer will be useful only if the people listen to the answer: “Figure it out and don’t waste it. I already sent you rain.” I agree that creativity is needed.
Desalination plants and water imported from the Great Lakes could not be accomplished quickly and the cost, including pipeline transport, might be prohibitive. Wells tapping the aquifer might help. Someone should be paid to investigate. Lake Superior is down 5 feet (which is huge) and Michigan will fight a Great Lakes drain, like Texas would if we tried to take its oil.
For now, using the water we saved (in Lanier and Allatoona) from several years ago seems a lot more productive solution than throwing it away and trying to pump in a replacement from far away. Write your congressman and senators like I did. It will rain eventually. We just need to plan now for larger reservoirs and we immediately need the ability to stop imprudent releases.
For now, when the level falls “below the normal pool,” our water quality will suffer. I’ve bought filters and hope they will work.