Is it time to start thinking about the worst-case scenario on Lake Mead?
It seemed like Colorado River basin states were ahead of the curve in 2007 when we enacted a 20-year set of guidelines that spelled out what would happen if Lake Mead were to ever fall into a shortage. But a decade later, as water levels at the lake plummeted, it was clear that we hadnt planned nearly enough for shortage. A stress test that better accounted for more recent drought conditions revealed that if we didnt do more to prop up water levels, there was an unacceptably high chance of the lake tanking within a few years. That hydrology helped solidify support for even more stringent cuts in the Drought Contingency Plan that overlaid the 2007 guidelines. But now, just two years in, were facing roughly the same chances of falling back into danger territory again. And the prospect of meeting once again to hammer out even more painful cuts before the guidelines expire in 2026. That doesnt mean the extra work weve done  or the science that helped drive it  was a failure. Both have saved Lake Mead from a far worse fate than if we had stuck with what we knew in 2007. The Colorado is growing drier, but also more volatile  Thats a key question for states leading up to 2026, as we negotiate the next 20 years of guidelines for the river. And a challenge for Arizona as it creates models to help assess the potential impacts of ideas that arise in those negotiations. Some have said that we should be even more aggressive in modeling potential futures to match the range of possibilities we could face. It remains an open question whether we are at the beginning of a mega drought or some other dry pattern weve seen before, or if climate change is moving us into uncharted territory that would require even more wild assumptions than what past data might reveal. The last 12 months have been the driest on record for Arizona. Scientists are still scratching their heads about how the latest heat wave  which started earlier and lasted longer than usual  fits in. But even if we could settle that debate, it doesnt necessarily mean that every year will be more of the same. Research suggests that while the basin is getting hotter and drier overall, many parts within it  including Arizonas Verde and Salt watersheds  are growing more volatile. Runoff in any given year could be a case of feast or famine. Model the worst case, at least to inform the debate  Some say the answer lies in the worst-case scenario. Instead of just looking at whats most likely to happen, they argue that we should also model for at least one black swan scenario. Borrowing a term from the financial industry, black swan events arent likely to happen in any given year but could have disruptive or even catastrophic consequences if they do. It makes sense. If were already modeling a range of futures, we should incorporate at least one that may seem outlandish now. That doesnt necessarily mean we have to act on what it says. But its worthwhile to know how fallowed farmland, additional cuts in the lower basin, a cap on growth in the upper basin or any other ideas to solve the Colorados fundamental supply-and-demand problems might play out in a black swan setting, and compare that to the futures that we think are most probable today. Because while most water planners have bought into the notion that climate change is increasing the risk of catastrophe, Im not so sure that our elected leaders  much less the wider public  have. We dont have to be alarmist. But we do need to know and very publicly discuss what might happen should things go south in a hurry. Because in this hotter, drier, more volatile future, they certainly can. Such an analysis could help reveal weaknesses in the system. Not to mention that, especially with water, the last thing we want to hear is jeez, I didnt see that coming.  Reach Allhands at joanna.allhands@arizonarepublic.com. On Twitter: @joannaallhands.