Dependable Erection

Thursday, December 06, 2007

The missing number?

In the context of explaining that the city has no plans to institute a "knee-jerk" moratorium on future development plans in light of the current water shortage, elected officials in the city and county expressed mostly satisfaction with a presentation of long term plans to increase water supply yesterday. Click for coverage in the N&O and Herald Sun, and commentary from BCR.

Reading through all of that, there's a number i think is still missing from the equation. I'm going to try to get to it.

Water officials are projecting a population of 337,000 people thirty years or so from now, up from approximately 220,000 today. Let's assume they're right. They're also projecting a demand of 41 million gallons per day, or about 120 gallons per person. (There are no separate figures provided for industrial use, so i'm assuming that is rolled into the overall demand figure.) Here's a chart of recent usage in Durham:


We crossed below the 120 per day per person threshold (26 mgd, based on a current population of 220K) in early November, after outdoor watering was banned and Stage III mandatory conservation measures enacted. Prior to that we averaged more like 136 gallons per day per person, or 13% higher consumption, and as much as 145 gallons per day per person during the summer months. So, the first question to ask is, i think, is the 41 mgd assumption for 2035 correct? Unless conservation measures are put into effect on a permanent basis, one could just as easily assume demand of 49 mgd, nearly 20% higher.

The real question, though, and the number that is missing from all of the articles, is what is the total capacity of the system in terms of the number of days of water available? It's one thing to say that all of the sources, when implemented, will be able to provide 54 mgd, which would appear to be a sufficient amount. Matt noted recently that some experts think the region has been in a drought for the last decade. This year, we had a surplus of rain through April or May, and a severe deficit since then. To have a full 6 month supply of water, at 54 mgd, requires 9 billion gallons of capacity. To store enough water for a year will require about 18 billion gallons. Teer Quarry adds about 1.5 billion in new capacity. How much do the other plans add? How much storage is the minimum in a changing environment? Those are the missing numbers.

Clearly, a moratorium on development does nothing to address the critical, immediate situation. But do our plans provide the capacity we need to accomodate both anticipated growth and the possibility that years like 2007 will be more common than "one in 50?" The answer better be an emphatic yes if our elected officials are unwilling to consider saying no to new development once in a while.

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3 Comments:

  • Two things bother me here: 1) the assumption that if they don't live near us, they're not a problem. They are. They're just someone else's problem -- but we all live on this planet together. And 2) There seems to be an assumption that there is a 1-to-1 correlation between development and the impact on natural resources, i.e., that every new person moving into a newly developed area is going to require the same amount of resources as someone living in an older area, and thus our systems will automatically be overburdened if we continue to allow development.

    I made this same assumption a few months ago, when the drought was fist emerging as serious, and discussed it with someone who works for the water authority in Orange County. I was surprised to learn that the issue is far more complex and it's not necessarily a given that new development spells trouble.

    For one thing, apparently new development uses low flush toilets, saving huge amounts over older properties, and usually include other more recent energy-saving innovations. If a person moves out of a water-wasting residence into a new one, you can actually save on the overall water needed. And these new residents pay both taxes and going rates for utility services. So the positive economic impact they can have on utility revenues can help fund alternate sources of resources or more efficient systems for using them. There was also a big difference between the pressure put on a water system by residential development vs. commercial.

    The bottom line seemed to be that cutting off development was not really much of an answer to problems like drought, especially since it just transfers the people who might have lived in a new area to another area, or keeps them n their existing area, leaving other jurisdictions to deal with the problem of not enough water (i.e., it's a bit of a "not in my back yard" challenge.") It's a much more macro problem than just local water supply conditions and needs to be addressed within a broader context.

    I think a more useful reaction would be to demand ultra-responsible development from a natural resources standpoint that uses state-of-the-art conservation and sustainability techniques, including how the homes are built and landscaped (visit The American Home at NC State for a cool view of what could be done). That way, instead of transferring the problem to someone else, we're modeling good behavior and making sure at least one neighborhood in this world uses the smallest possible environmental footprint.

    By Anonymous Coconut, at 3:35 PM  

  • I was at the Joint City-County Planning Committee meeting yesterday where this was discussed.

    The 120 gallon per capita number (which includes ALL uses divided by the population) is the average over the last few years. The numbers fluctuate seasonally. Apparently the number that planners use, the one that was used in our comp plan, is 170 gallons per capita. In fact, demand peaked about 2000, IIRC, and has gone down since then. That really surprised me.

    There was some discussion about this phenomenon. and Ted Voorhees, ass't city manager said that while it was still a mystery, it might be a result of some water-intensive industries leaving Durham. Low flush toilets are certainly a factor. I find that the biggest water user in our house is the washing machine, and new machines use much less water. There it is--the Bocckino hypothesis.

    Coconut is right on the money. New development should be geared towards water conservation-- toilets, appliances and native plants or xeriscaping.

    By Anonymous steve bocckino, at 4:10 PM  

  • Interesting points.

    as far as the nimby issue goes, water resources are unevenly distributed throughout the country, and in some areas are not a limiting factor in how much population can be supported in the region.

    not to say that there aren't other factors.

    people also don't necessarily live and work in the same town. i work in Hillsborough, for instance, and live in Durham. i live in an older home, but one of the toilets is a low volume toilet, and the other has a gallon of displacement (plus we only flush it when necessary and then refill it by hand with reclaimed shower water.) New development means higher population overall, with more water usage at work, for more restaurants, more schools, etc.

    it is a very complex issue without a simple solution. but at this point i think it's a mistake to take any options off the table.

    By Blogger Barry Ragin, at 4:59 PM  

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