Though I'm often one to criticize our local officials for head-scratcher decisions and bonehead ideas, I'm a bit surprised to see the recent dust-up over the change in how Durham's calculating days remaining of water supply.
Barry kicked this off over at his place yesterday with a piece on the "missing MGD" -- that is, the gap between the 17.75 million gallons/day of water that Durham was using to calculate the days of water remaining, and the fact that the actual water demand was 20.94 MGD.
The plot thickens in today's N&O coverage:
Durham doesn't factor in the full daily demand to calculate how much water it has left in its three main reservoirs. If it did, it would have about 106 days of water in its main supplies, about three weeks less than the 125 it's touting now.
The city's average daily demand for January is 20.95 million gallons. But to calculate the days left, only 17.74 million gallons is divided into the total water available in Lake Michie, Little River and Teer Quarry reservoirs.
There's two issues here. Is the calculation sound? And, was this communicated as well as it could be?
To the first point, I think there's absolutely no question that subtracting the OWASA/Cary inflow from Durham's actual water use to get the 17.75 MGD number is the right way to go.
After all, the crucial immediate question for Durham in the drought is, how long until the Durham-owned reservoirs run dry? The answer is a simple math exercise from any B-school's operations management class. You take the fixed quantity of reserve supply in fixed units, divide by the units per day of usage, and get a number of days remaining.
That calculation would work great for a closed system in which all demand was being met from Durham's own supplies. The wrinkle, though, is a good one: Durham is increasingly drawing water from outside its supplies. Today, as much as 4 MGD from OWASA and Cary; by summer, as much as 11 MGD.
Those flows don't go into Little River and Lake Michie; they go into the Durham water supply to meet daily demand. Since they're flows and not fixed supplies, the only reasonable way to make the math work is to subtract those inflows from Durham's daily demand.
The one asterisk that rides with these numbers is the question of whether Cary's system could continue to supply Durham if the drought worsens. As of today, however, the towns that draw from Jordan Lake are eligible to pull 49 MGD from the huge reservoir; last year's all-time peak was around 28 MGD. And Jordan Lake, as we learned at the recent Duke-Durham drought forum, has barely been touched by the current drought.
Now, I'm no waterologist -- but in the absence of more information that suggests reasons to be concerned, I'm not particularly worried about Jordan Lake yet.
Which brings us to the second issue: Could Durham officials communicated this more clearly?
Sadly, as is often the case, the answer seems to be yes. Not that it was a seeming attempt to hide or deceive; the actual daily water usage numbers on the graphs showed, plain as day, the 21 MGD of actual usage that Barry noted. It wouldn't have been hard for the City to put a quick disclaimer on their web site noting that the inflows from other systems were used in the calculus of water supply remaining.
And I don't begrudge Mayor Bell using the higher number (193 days) in the State of the City speech. After all, the City was called to act, and did act -- bringing Teer Quarry online as a stopgap, and rushing the expansion of water supply interconnections.
The obvious problem here is, as usual, perception. And that's a lesson the City never seems to get right. We're only two months out from the ill-fated lack of communication over the E. Chapel Hill St. parking deck -- the contemporaneity of which with Patrick Baker's move to the City Attorney slot sometimes seems too close for coincidental comfort.
The bigger problem, though, is the risk that a public thinking there's nothing to worry about with the water supply stops caring... stops conserving... stops demanding City leaders make long-term fixes to get us ready for the next drought.
And that's the one area where the new, new water math really doesn't add up.