Still using the wrong numbers
From the Herald Sun:
78 million gallons per day does not measure storage capacity. It measures deliverability. If the water is not there, it doesn't matter how much of it you can deliver, now does it? Using the 78 million gpd number, a 6 month supply of water would total a little over 14 billion gallons. given the recent trend of rainfall, that is, three of the past seven years have seen significant shortages lasting 4-6 months or more, having a six month supply of water would seem to be the minimum acceptable level. OWASA, for example, had about a 7 month supply before the end of year rains last week. Using the numbers posted on the city of Durham website (112 days of premium water at 19.3 million gallons per day) the city's total water supply is a little over 2.1 billion gallons*.
Using a more reasonable 30 million gallons per day, a six month supply would need to be about 5.5 billion gallons. On the other hand, a pre-conservation effort 30 million gpd would place the current supply at about 80 days.
It may well be that the city water planners are using these figures in their internal deliberations. But they need to start using them in talking to the public as well, if that's the case. The key figure is not how many millions of gallons per day the system can deliver. The critical issue is how many days of water supply can the system hold, and how close to that capacity are we going to be able to keep it?
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* To clarify, i'm only using the premium numbers, and not the total number here, which includes water below the intakes which is more expensive because it needs to be pumped and because it's going to have more junk in it which needs to be filtered out before using it. If we get to the point where that's all that's left, we can truly consider ourselves in crisis mode.
"The point is, we see now that all the predictions are that this drought is not going away anytime soon," Commissioner Becky Heron said. "We need to be careful what obligations we put on our utilities."
City administrators, however, have voiced confidence in their long-range planning.
Durham's existing reservoirs, Lake Michie and Little River, can usually supply about 37 million gallons of water a day. The city intends to use an abandoned quarry off Denfield Street for additional storage. When it's fully online, the system's capacity would rise to about 44 million gallons day.
The city further intends to draw about 10 million gallons a day from a regional reservoir, Jordan Lake. Eventually, it plans to expand Lake Michie, bringing another 24 million gallons of water a day in capacity online.
All that totals about 78 million gallons a day of potential capacity.
78 million gallons per day does not measure storage capacity. It measures deliverability. If the water is not there, it doesn't matter how much of it you can deliver, now does it? Using the 78 million gpd number, a 6 month supply of water would total a little over 14 billion gallons. given the recent trend of rainfall, that is, three of the past seven years have seen significant shortages lasting 4-6 months or more, having a six month supply of water would seem to be the minimum acceptable level. OWASA, for example, had about a 7 month supply before the end of year rains last week. Using the numbers posted on the city of Durham website (112 days of premium water at 19.3 million gallons per day) the city's total water supply is a little over 2.1 billion gallons*.
Using a more reasonable 30 million gallons per day, a six month supply would need to be about 5.5 billion gallons. On the other hand, a pre-conservation effort 30 million gpd would place the current supply at about 80 days.
It may well be that the city water planners are using these figures in their internal deliberations. But they need to start using them in talking to the public as well, if that's the case. The key figure is not how many millions of gallons per day the system can deliver. The critical issue is how many days of water supply can the system hold, and how close to that capacity are we going to be able to keep it?
======================
* To clarify, i'm only using the premium numbers, and not the total number here, which includes water below the intakes which is more expensive because it needs to be pumped and because it's going to have more junk in it which needs to be filtered out before using it. If we get to the point where that's all that's left, we can truly consider ourselves in crisis mode.
Since 1949, Durhamites have slept soundly, secure in the knowledge that, in our town, erection can be depended upon. Now, thanks to the power of the internets, we can spread that security all over the world.
4 Comments:
I know this is a misanthropic view but there is a potential good to come out of this drought. Maybe we can get the population here to decrease some. Stop some of the development. :)
-sv
By
skvidal, at 12:35 PM
Interesting analysis, Barry. I think your idea of a guaranteed 6-month supply would make great public policy.
You are right, it's not carrying capacity that matters. All the capacity in the world doesn't help if the lakes are empty.
I'd like to see an estimate from the Durham water people of the amount of annual rainfall it would take to balance increasing demand levels. I believe those estimates would depend on the size of the watershed feeding each reservoir and our dependency on each source. Jordan Lake's watershed is vast, hence it's our safest source of water. According to a state meteorologist, we've been in a drought since 1998, IIRC. What happens if we extrapolate those rainfall amounts into the future?
I have been very reluctant to support curbs on development as a reaction to the current drought, but we need a critical analysis of our future needs now. If our water supply cannot support our 2% rate of growth, rezonings can be slowed or even halted. It's complicated though.
Durham's water demand has been flat for some time (surprised the hell out of me!) , implying that new houses are more efficient than old and that new toilets, washing machines and dishwashers make a big difference. About 1/2 of our growth is Durhamites making new Durhamites. If we stopped all development, where would today's Durham babies live tomorrow?
I ran into a pro-development political friend at a party last month. He shocked me by saying he supported a development moratorium. Maybe he's right.
By
Anonymous, at 5:39 PM
just wanted someone in the 'hood areas to blog about this because it pissed me the hell off when i read it...
http://www.newsobserver.com/news/saunders/2007/story/861811.html
i hope Barry Saunders is happy in his snazzy lil hat when he CANT flush his toilet...and next time check with actual people outside of high end suburbs and ask if they're not flushing their toilets as much...
cause we're not...
By
Anonymous, at 3:16 PM
i actually like Barry's hat.
but you're right. that column was an insult to those of us who are saving water every chance we get. thanks for reminding me about it. i'll try to post something on the front page tonight.
By
Barry, at 3:25 PM
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