Correction appended, I was off by 5kaf on the Nevada numbers
With the backdrop of Hoover Dam, an assembly of Colorado River dignitaries signed the Drought Contingency plan yesterday afternoon.
Done really is done. The Colorado River Drought Contingency Plan or DCP is now official. pic.twitter.com/35PhTojepU
— Jeffrey Kightlinger (@8thGenCA) May 21, 2019
Now that we have a DCP, what does this mean in practice?
According to the most recent Bureau of Reclamation 24-month study, Lake Mead is projected to end 2019 at elevation ~1,085 feet above sea level. Prior to the DCP, Lower Basin water users (Mexico, Arizona, Nevada, California) got a full allocation of water as long as Lake Mead’s elevation was above 1,075. Under the DCP, a new shortage tier has been added between elevations 1,090 and 1,075. The result is that, for the first time in the history of Colorado River management, there will now be mandatory water use reductions on the Colorado River.
What does this mean in practice? I ran down a quick summary this morning of the relevant data, comparing recent use with the cuts mandated under the DCP. It shows that, at this first tier of shortage, permitted use is less than the voluntary cuts water users have been making since 2015:
|in millions of acre feet||Arizona||Nevada||California||total|
|2015-2019 average, without DCP||2.578||0.242||4.234||7.054|
|2020 permitted, with DCP||2.608||0.292||4.4||7.3|
In other words, all of the states are already using less water than contemplated in this first tier of DCP reductions.
The details, by state:
Arizona’s full allocation is 2.8 million acre feet of water per year. In this new first year of shortage, Arizona will only be allowed to take 2.608 million acre feet of water, a 192,000 foot reduction.
This year, without any DCP, Arizona plans to voluntarily take larger reductions. The current forecast puts Arizona’s 2019 draw on the river at 2.515 million acre feet. Last year, Arizona took 2.639 million acre feet, according to the Bureau of Reclamation’s preliminary year-end accounting.
Here’s a summary of recent years:
Arizona Without DCP:
- 2015: 2.601 maf
- 2016: 2.613 maf
- 2017: 2.510 maf
- 2018: 2.640 maf
- 2019: 2.515 maf
Arizona with DCP:
- 2020: 2.608 maf
Nevada’s full allocation is 300,000 acre feet of water per year. In this new first tier of shortage, Nevada will only be allowed to take 287,000 acre feet of water.
This year, without any DCP, Nevada plans to voluntarily take larger reductions. The current forecast puts Nevada’s 2019 draw on the river at 263,000 acre feet, but because of the way the forecasting is done, that will almost certainly go down. Last year, Nevada took 244,000 acre feet of water.
Nevada without DCP:
- 2015: 220 kaf
- 2016: 238 kaf
- 2017: 243 kaf
- 2018: 244 kaf
- 2019: 263 kaf (but likely to drop)
Nevada with DCP:
- 2020: 292 kaf
California’s full allocation is 4.4 million acre feet of water per year. California takes no cuts in this first tier of shortage
This year, California plans to take significant voluntary reductions. The current forecast puts California’s 2019 draw on the river at 4.064 million acre feet. Last year, California took 4.253 million acre feet of water.
California without DCP:
- 2015: 4.494 maf
- 2016: 4.381 maf
- 2017: 4.026 maf
- 2018: 4.253 maf
- 2019: 4.064 maf
California with DCP:
- 2020: 4.4 maf