Water managers were all smiles recently when the Colorado River Drought Contingency Plan (DCP) became official, providing an overlay on the Colorado River Basin’s 2007 Shortage Sharing Guidelines.
At about the same time, there was more to celebrate as the U.S. Bureau of Reclamation released its April 24-Month Study, which strongly suggests that at the end of 2019, Lake Mead will be above the Tier 1 shortage trigger of 1075’ elevation.
That’s all good news, right?
However, there’s one component to DCP that didn’t receive a lot of public attention – a new Tier Zero shortage trigger at 1090’ elevation. Since the lake currently sits between 1090’ and 1075’ (the Tier 1 trigger), it is most likely Arizona will be in a Tier Zero shortage in 2020.
Now it’s time to take a closer look at Tier Zero shortage and its implications under the newly enacted DCP legislation.
The small purple dots on this map show the Tier Zero (less than 1090’ elevation) realities. For Arizona, a Tier Zero shortage means our Colorado River supplies will be reduced by 192,000 acre-feet, falling almost entirely on CAP. In a Tier Zero shortage, supplies to Nevada and Mexico will also be reduced and the Bureau of Reclamation will begin making contributions to Lake Mead.
The 192,000 acre-feet reduction to CAP, about 12% of the normal CAP supply, is essentially equivalent to the amount we have been voluntarily leaving in the lake since 2015 as part of our Lake Mead Conservation program. The difference is that those contributions were voluntary; under DCP these contributions become mandatory.
Presently, CAP’s 2020 Water Plan and Base Rates use this Tier Zero shortage assumption. Tier Zero means there is no extra CAP water available for banking or replenishment. In addition, the CAP agricultural users will suffer about one-third reduction in supply. These reductions are painful and increase CAP water rates. However, even with these reductions, CAP and our partners will continue to conserve resources to prepare for a drier future.
All in all, the fact that we likely won’t enter a Tier 1 shortage is encouraging news. Although, as we know, one great winter does not erase nearly two decades of drought. Working under the new realities of DCP, we now have a road map for the next several years. We’ll be working under DCP until 2026, at the same time as we roll up our sleeves again to negotiate the new shortage-sharing guidelines that will be in place after that. After all, a water manager’s work is never truly done!