There have been ongoing negotiations for several years directed at developing the new Colorado River management guidelines that will go into place in 2026 when the 2007 interim guidelines expire.
The goal of negotiations among the seven U.S. Colorado River basin states has been to submit a single document proposing guidelines to the Bureau of Reclamation (BoR) within the U.S. Department of the Interior. However, the upper and lower basin state groups have been dealing with significant differences and were not able to come to a consensus agreement. As a result, the upper and lower basin delegations each submitted separate proposals to the BoR in early March.
Both proposals are under review by the BoR officials who have indicated that they will be working with the basin states in the next six months to develop a consensus draft proposal for post-2026 river management by the end of 2024.
To help review the differences between the two proposals, I have summarized the basic parameters in Tables 1 through 4 (Davis, 2024a and Hager, 2024a).
To help review the differences between the two proposals, I have summarized the basic parameters in Tables 1 through 4 (Davis, 2024a and Hager, 2024a).
Lower Basin Proposal Summary
Table 1. Outline of lower basin proposal for Colorado River water management based on reservoir levels of Lakes Powell and Mead.
|
Reservoir Levels (%) |
Lower Basin Reductions (MAF/Year)* |
Upper Basin Reductions (MAF/Year) |
|
70 |
0 |
0 |
|
59-69 |
0-1.5** |
0 |
|
39-58 |
1.5 |
0 |
|
≤ 38 |
X |
X |
Note:
*MAF = million acre-feet
**Up to 1.5 MAF/year reductions for the entire lower basin depending on the reservoir levels between 59-69%. Divisions of water reductions among the lower basin states is not specified.
X = 1.5-3.9 MAF/year total reductions for the total Colorado River system. The specific amounts of water reductions in each of the upper and lower basins with reservoir levels at 38% or less are not specified in the current lower basin proposal.
Table 2. Annual reductions in Colorado River water allocations for the lower basin states when the reservoir water levels are between 39-58% in both reservoirs, based on the lower basin proposal.
|
Lower Basin State |
Reduction (acre-feet) |
|
Arizona |
760,000 |
|
California |
440,000 |
|
Nevada |
50,000 |
|
Mexico* |
250,000 |
*Contingent upon Mexico’s agreement with the reductions.
Based on the lower basin proposal, reservoir levels at 38% of capacity and lower would result in reductions from 1.5 to 3.9 MAF/year, depending on the levels of water depletion in Lakes Powell and Mead. The exact splits in water reductions between the upper and lower basins in this range of reservoir depletion is not specified in the lower basin plan, at least based on the materials used for this review. Accordingly, the share of water reductions that Arizona and California would take are not specified either.
For reservoir levels of less than or equal to 38%, the cuts would gradually tighten until the reservoirs fall below 23% of capacity. At that point, all Colorado River basin states would have to take maximum collective reductions of 3.9 million acre-feet a year.
Upper Basin Proposal Summary
Table 3. Outline of reductions in water releases from Lake Mead based on the upper basin proposal.
|
% of Capacity |
Release Reductions (MAF/year)* |
|
90 |
0 |
|
70-90 |
0-1.5 |
|
20-70 |
1.5 |
|
≤ 20 |
1.5-3.9 |
*MAF = million acre-feet
Specifically for Lake Mead, the Upper basin states proposal includes points:
— If Mead is at least 90% full, the Lower Basin states would take no cuts in their supplies.
— If Mead is between 70% and 90% full, the Lower Basin states would lose up to 1.5 million acre-feet per year.
— If Mead is 20% to 70% full, Lower Basin states would lose 1.5 million acre feet a year.
— If Mead is 20% full or lower, Lower Basin states would have to take cuts of up to 2.4 million acre-feet on top of the 1.5 million they’re already taking.
For Lake Powell, the Upper Basin states proposed a series of shrinking water releases depending on the lake’s elevation:
— If Powell is 81% to 100% full, the lake will release anywhere from 8.1 to 9 million acre-feet of water annually to send to Lake Mead for use by Lower Basin states.
— If Powell stands anywhere from 20% of 81% full, the lake will release somewhere between 6 million and 8.1 million acre-feet a year to Mead.
— If Powell is less than 20% full, it will send to Mead 6 million acre-feet a year.
Table 4. Outline of water releases from Lake Powell based on the upper basin proposal.
|
% of Capacity |
Lake Powell Water Release (MAF/year)* |
|
81-100 |
8.1-9 |
|
20-80 |
6.0-8.1 |
|
< 20 |
6.0 |
*MAF = million acre-feet
It is important to note that the upper basin proposal puts the entire reduction of Colorado River water use on the lower basin states. Essentially, the upper basin states see the need for Colorado River water reductions as lower basin responsibility entirely.
To help keep the conversation interesting, the Gila River Indian Community (GRIC) Governor Stephen Roe Lewis announced on 13 March 2024 at the University of Arizona Water Resource Research Center Annual Conference in Tucson, Arizona (WRRC, 2024) that their community is opposed to the lower basin proposal and with a letter to the BoR, GRIC is seeking to reinforce their existing rights to water and gain a stronger place and voice in the negotiations regarding future access to Colorado River water via the Central Arizona Project (CAP). Sixteen other tribes in the Colorado River basin signed the 11 March letter from GRIC to the BoR. Eight of those tribes are from Arizona (Davis, 2024b and Hager, 2024b).
The GRIC and some other tribes are pushing for the BoR to find other supplies of water to replace any water that is cut from CAP deliveries or provide financial compensation, particularly to cover existing and/or potential tribal water rights for Colorado River water.
There are many interesting ramifications that are possible from these recent developments. The BoR has two proposals to review from the upper and lower basins and now the added dimension of the GRIC opposition. These recent requests from GRIC and some other tribes will need to be taken into consideration along with the proposal elements from both the upper and lower basins.
References
Davis, Tony. 2024a. States are far apart on new Colorado River water-saving plans sent to U.S. agency. Arizona Daily Star, 13 March 2024.
This study was conducted at the Yuma Valley Agricultural Center. The soil was a silty clay loam (7-56-37 sand-silt-clay, pH 7.2, O.M. 0.7%). Spinach ‘Meerkat’ was seeded, then sprinkler-irrigated to germinate seed Jan 13, 2025 on beds with 84 in. between bed centers and containing 30 lines of seed per bed. All irrigation water was supplied by sprinkler irrigation. Treatments were replicated four times in a randomized complete block design. Replicate plots consisted of 15 ft lengths of bed separated by 3 ft lengths of nontreated bed. Treatments were applied with a CO2 backpack sprayer that delivered 50 gal/acre at 40 psi to flat-fan nozzles.
Downy mildew (caused by Peronospora farinosa f. sp. spinaciae)was first observed in plots on Mar 5 and final reading was taken on March 6 and March 7, 2025. Spray date for each treatments are listed in excel file with the results.
Disease severity was recorded by determining the percentage of infected leaves present within three 1-ft2areas within each of the four replicate plots per treatment. The number of spinach leaves in a 1-ft2area of bed was approximately 144. The percentage were then changed to 1-10scale, with 1 being 10% infection and 10 being 100% infection.
The data (found in the accompanying Excel file) illustrate the degree of disease reduction obtained by applications of the various tested fungicides. Products that provided most effective control against the disease include Orondis ultra, Zampro, Stargus, Cevya, Eject .Please see table for other treatments with significant disease suppression/control. No phytotoxicity was observed in any of the treatments in this trial.
Interested in the latest developments in automated weeding machines? There are a couple of opportunities at the upcoming 2024 Southwest Ag Summit to stay up to date. One is the “Ag Tech: Innovations in Weed Control Technologies” breakout session where university experts and cutting-edge innovators will provide updates on the latest advances in AI, laser weeding, high precision smart spot sprayers, robotic/automated weeders and band steam (agenda below). The session will be held Thursday, February 22nd from 1:30-3:30 pm at Arizona Western College (AWC) in Yuma, AZ.
The other is the Southwest Ag Summit Field Demo on February 21st, where several of these technologies and other state-of-the-art automated weeders will be demonstrated operating in the field. The Field Demos will also be held at AWC. Breakfast will be served at 7:00 am and demonstrations begin at 8:00 am.
For more information about the Southwest Ag Summit, visit https://yumafreshveg.com/southwest-ag-summit/.
Fig. 1. Agenda for the “Ag Tech: Innovations in Weed Control Technologies”
educational session at the 2024 Southwest Ag Summit. The session will be held
Thursday, February 22nd at Arizona Western College, Yuma, AZ.
Fig. 2. 2024 Southwest Ag Summit Field Demo agenda. The event will be held at
Arizona Western College in Yuma, AZ.
Results of pheromone and sticky trap catches can be viewed here.
Corn earworm: CEW moth counts down in all traps over the last month; about average for December.
Beet armyworm: Moth trap counts decreased in all areas in the last 2 weeks but appear to remain active in some areas, and average for this time of the year.
Cabbage looper: Moths increased in the past 2 weeks, and average for this time of the season.
Diamondback moth: Adults increased in several locations last, particularly in the Yuma Valley most traps. Below average for December.
Whitefly: Adult movement remains low in all areas, consistent with previous years
Thrips: Thrips adult movement continues to decline, overall activity below average for December.
Aphids: Winged aphids still actively moving but declined movement in the last 2 weeks. About average for December.
Leafminers: Adult activity down in most locations, below average for this time of season.
