On Tuesday, 15 August 2023 officials from the U.S. Bureau of Reclamation (USBR) presented their 24-Month study reports with projections and operational plans for 2024 (USBR, 15 August 2023). We are still dealing with the drought but there is some improvement in the 2024 plans for Colorado River water allocations for Arizona.
The wet winter and spring experienced in the Southwest in 2023 has provided some relief on the dire situation we were facing on the Colorado River system and reservoir levels have improved. But unfortunately, one good precipitation season does not solve all the problems and they will still need to be dealt with.
The current plan for lower Colorado River water management is basically a return to the Drought Contingency Plan (DCP) Tier 1 schedule (Figure 1).
Fgure 1. Drought Contingency Plan Tier reductions for Arizona.
Tier 1 plans take us back to an 18% reduction or 512,000 acre-feet (KAF) of Arizona’s Colorado River allocation of 2.8 million acre-feet (MAF). Arizona was operating under Tier 1 guidelines in 2022.
The irrigation districts in central Arizona that have lost access to Central Arizona Project (CAP) water will not be receiving any additional water in 2024 based on this plan. The districts immediately adjacent to the mainstem of the Colorado River will continue to receive the same amount of water as they have been receiving the past two years. For Arizona and the other lower basin states, these are basically the same water allocation guidelines that were in place in 2022.
The urban areas and American Indian tribes will not experience any additional reductions based on the USBR plans. However, some cities and tribes have volunteered to reduce their Colorado River water allocations in exchange for payments from the federal government.
For example, in 2023 Arizona, California, and Nevada agreed to a plan that will conserve an additional 3 MAF of Colorado River water through 2026 in exchange for $1.2 billion from the federal government. If approved by the USBR, this plan would reduce Colorado River allocations to the Imperial Irrigation District in California, which has some of the most senior water rights on the river.
The Gila River Indian Community (GRIC), which has a Colorado River allocation of 653 KAF, committed in April 2023 to relinquish temporarily 125 KAF in exchange for $400 per AF from the federal government. The federal government is also funding GRIC infrastructure projects to increase wastewater reuse in irrigation.
Thus, some of the Colorado River water that is technically allocated to Arizona under Tier 1 guidelines will stay in Lake Mead due to previously agreed upon conservation measures.
Regarding other lower basin states and the current USBR plan, Nevada will have slightly more Colorado River water in 2024 than in 2023. Mexico will deal with a 5% reduction in Colorado River water from their base and once again California will not be suffering any required cuts in their Colorado River water allocation.
Overall, this is good news. We have some temporary relief on the Colorado River system and no additional reductions will be required in 2024. This puts the seven Colorado River basin states and Mexico in a better position to negotiate the guidelines and agreements required for 2026 since all the existing agreements expire in two years.
Reference
USBR, 15 August 2023. 24-Month Study reports.
August 2023 Lake Powell and Lake Mead: End of Month Elevation Charts
I am seeking samples of downy mildew on lettuce from around Yuma County to support the Michelmore Lab and their ongoing efforts to help characterize the downy mildew populations of the United States. The Michelmore Lab has led the charge on a survey of Bremia variants since 1980 and has been instrumental in demystifying the gene-for-gene nature of lettuce resistance to downy mildew.
Their group invites growers across the United States to submit downy mildew infected plant samples, which are then used to culture the Bremia on live host plants. The team then inoculates a panel of lettuce varieties carrying known resistance genes to determine the race of each isolate they receive. Identifying which races occur in which specific fields is essential to guiding the breeding of new resistant cultivars and maximizing the effectiveness of host-based genetic disease management. The data obtained from these tests are also used to designate new Bremia races through the International Bremia Evaluation Board.
Your contribution will help breed better lettuce for Yuma. This means less breakdown of resistance in the field, and better yields for Yuma growers. To facilitate these submissions the Yuma Plant Health Clinic will be setting up a separate drop-off point and submission sheet for downy mildew sample submissions in the same hallway we use for standard plant diagnostic submissions. The drop-off point will be clearly labelled and consist of a chest-style refrigerator and printed copies of the submission form. It is vital to keep these samples cool so they remain viable for future inoculations, so please place your samples inside of the refrigerator before you leave.
Shipping will be handled by the clinic. All we ask is that you fill out the submission form as completely as you can. An example of the questions that are asked in that form so you can prepare ahead of time can be found HERE .The Yuma Fresh Vegetable Association recently published a video about vegetable crop production in Yuma, AZ. The video is comprehensive, covering everything from Yuma’s ag beginnings, to details on current cultivation practices, to the uniqueness and importance of the region to our national food security. The story is a good one and very well told. Even if you’re well versed in Yuma agriculture, I think you’ll find the piece interesting and informative.
Check it out by clicking here or on the image below.
Fig. 1. Yuma Fresh Vegetable Association’s “Yuma – The Winter Salad Bowl” video. (Photo Credit: Yuma Fresh Vegetable Association)
Growers and PCAs asked about the potential injury that can be caused by a mix of RoNeet (Cycloate) with Dual Magnum (S-Metholachlor) to spinach. We did a small evaluation including the treatments suggested by our friends to collect data. A 1.33pt rate for Dual M and 4.0 pt of RoNeet was sprayed for this trial. The lower Dual M recommended rate by the SLN for AZ in 2017 of 0.33 - 0.67 pt per acre was not included in the trial1. Here’s the treatment list:
Plots consisted of two rows 30ft long replicated four times with 10 seed lines, and the test was established in a randomized complete block design with four replications. All treatments were applied preemergence. A CO2 backpack with a 4 flat fan nozzle boom spaced at 20” was used delivering 20 gallons/acre.
Planting was done on Nov 17, 2022, then the next day the treatments were applied and incorporated immediately with sprinkler irrigation. Crop injury was evaluated on December 13, 21 and 27. The combination of RoNeet plus S-Metolachlor at the rates above mentioned presented the highest phytotoxicity symptoms in the form of chlorosis, stunting, and reduced stand. Also, Dual Magnum alone at the rate of 1.33 pt/a presented injury in lower proportion compared to the combination with RoNeet. In this evaluation the 4pt/a rate of RoNeet did not present injury to the spinach as you can see comparing with the untreated plots below. Weed control data was not collected due to inconsistent and low populations. Only phytotoxicity was evaluated.
The most representative images of the plots are below:
Figure 1. Preemergence herbicide injury evaluation on spinach
