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Tuesday, August 15, 2017

Finalizing the U.S./Mexico Water Sharing Agreement

A summary of a tentative agreement on shortage sharing in the Colorado River basin was recently released by the International Boundary and Water Commission (IBWC) - the bilateral international commission that implements the 1944 Rivers Treaty between the U.S. and Mexico. This agreement will be Minute 323 to the 1944 Rivers Treaty, and represents an extension of several of the main provisions of Minute 319, the 2012 agreement that expired this year. Minute 323 will only be finalized if the states of the Colorado River basin can agree on a Drought Contingency Plan (DCP). The DCP negotiations are ongoing. This agreement represents the continued success of the IBWC and emphasizes the importance of hydrodiplomatic relations between the U.S. and Mexico. Lost in much of the (in my opinion, misguided) talk of building walls on the border or abandoning NAFTA is the importance of a close, collaborative relationship between the U.S. and Mexico in jointly managing our rivers to enhance drought resiliency and our ability to adapt to changing climate conditions.

Minute 323 will extend Mexico's agreement to take a reduction of the 1.5 million acre-feet per year (maf/y) it is owed under the Rivers Treaty in times of shortage, declared by the U.S. Department of the Interior (DOI). Such declarations are based on the elevation of the water in Lake Mead. The agreement will also extend Mexico's ability to store a portion of its allocation in Lake Mead, which provides Mexico with needed storage capacity while also helping to avoid shortage declaration by keeping the reservoir's levels above 1,075 feet (the level below which a light shortage would be declared). Thanks to a good snow pack this past winter, the lake level today is 1,080.31, which is comparatively comfortable after several years of drought conditions and record-low reservoir levels. Under the DOI's shortage sharing guidelines, Arizona and Nevada face reductions if a light shortage is declared, and then further reductions in the case of a heavy shortage (below 1,050) and an extreme shortage (1,025). Below 1,000 represents dead pool - there is no guidance on shortage sharing at that stage (it's the Thunderdome). California currently faces no reductions (although that issue is part of the DCP negotiations). Mexico has voluntarily agreed to reductions in Minute 319, and will renew that commitment in Minute 323. Mexico's willingness to share in shortage and store its allocation in Lake Mead are enormously helpful to the overall management of the river. The legal regime governing the Colorado River has a built-in structural deficit. The Colorado River Compact allocates 7.5 maf/y to the Upper Basin states and 7.5 maf/y to the Lower Basin. The 1944 Rivers Treaty allocated 1.5 maf/y to Mexico, and we lose about 1.5 maf/y to evapotranspiration. That's 18 maf/y we assume in the river, and represents the foundation upon which the entire water rights regime in the basin is built. Yet we know from tree ring analysis that the 1,000 year average in the river is closer to 13 maf. We have to build in more adaptive capacity to respond to this structural deficit, and Minute 323 extends that needed flexibility that we secured in Minute 319.

Minute 323 also will include a few new elements not included in Minute 319. One will be the development of the "Bi-National Water Scarcity Contingency Plan" to create a long-term strategy for larger reductions in allocations in cases of extreme shortage. The other is the formation of working groups, including one to explore the joint development of desalination on the Sea of Cortez. I've written on the legal issues raised by that kind of joint development of desalination. It's one of other recent joint international desalination developments, including most notably the Red-Dead Project between Israel and Jordan. These kinds of projects are enormously complex and generally expensive. I am optimistic about the future of desalination, and the technology has made huge leaps in recent years. But we are often too quick to jump to costly augmentation projects without fully evaluating alternatives. All of the jurisdictions of the lower Colorado basin deal with significant water losses, caused in part by infrastructure challenges like unlined ditches or leaking pipes. Water savings from repairing pipes and lining ditches may provide the same quantity of water as desalination but at a lower cost. Other potential augmentation methods should also be considered, including a cooperative approach to upland forest management. The costs and water savings that could be achieved from such measures, or perhaps something even more ambitious like floatovoltaics (solar panels on the surface of ditches and reservoirs to generate energy while reducing evaporation losses) should be compared to costs and water generated from augmentation projects like desalination.



Posted by Rhett Larson on August 15, 2017 at 07:52 PM | Permalink


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