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January 26, 2022  |  Written by Daniel F. McCarl

In 500+ Plan, Lower Basin Undertakes New, Voluntary Conservation Effort to Protect Hydropower Production and Diminishing Storage Supplies in Lake Mead

In the Colorado River basin, water users can continue to expect more conservation projects in 2022, particularly in the Lower Basin states. In December, the Bureau of Reclamation and the Lower Basin states (California, Nevada and Arizona) entered into a Memorandum of Understanding (MOU) that aims to conserve an additional 1,000,000 acre-feet of water in Lake Mead, 500,000 acre-feet in each of 2022 and 2023. The MOU responds to troubling forecasts from Reclamation detailing the risk that water elevations in Lake Mead could fall below critical levels in the absence of new, additional actions.

As a voluntary effort primarily focused on reducing demand for water, the MOU’s water-savings plan – dubbed, the “500+ Plan” – stands out among other recent activities taken to address diminishing water supplies in the Colorado River Basin and protect hydropower generation at Hoover and Glen Canyon Dams. Earlier this month, for example, Reclamation announced that it would make operational adjustments to delay the release of 350,000 acre-feet from Glen Canyon Dam to help protect water elevations in Lake Powell.

Funding the 500+ Plan

The 500+ Plan relies upon financial contributions of “up to” $100 million from California, Nevada and Arizona to galvanize new water conservation efforts. The MOU contemplates that the federal government will match this amount, bringing total funds under the program to approximately $200 million.

“Additional” Water

The $200 million, half from the state-entities, half from the federal government, would be used to generate “additional water” savings in Lake Mead beyond what is required by the 2007 Interim Guidelines and the 2019 Lower Basin Drought Contingency Plan, the primary authorities that govern water operations in the Lower Basin States. See MOU, § 2.

That said, the negotiations that led to the 500+ Plan had their origins in a component of the Lower Basin Drought Contingency Plan which requires that:

If any 24-month Study for the minimum probable inflows projects that Lake Mead elevations will be at or below 1,030 feet anytime within the succeeding two Years, the Secretary and Lower Division States shall consult and determine what additional measures will be taken by the Secretary and Lower Division States to avoid and protect against the potential for Lake Mead to decline below 1,020 feet.

This provision was triggered by the Bureau’s August 2021 24-month study when the Bureau forecast that the water elevation of Lake Mead would fall below 1,030 feet in July of 2023 under its “minimum probable inflow” scenario. This scenario “reflects a dry hydrologic condition which statistically would be exceeded 90% of the time.”

While the expectation is that some of the additional water generated by the 500+ Plan will come from compensating farmers for fallowing their lands, the MOU as drafted provides maximum flexibility to meet its million acre-foot goal. See MOU, §§ 3, 7. Notably, the MOU does not identify any specific amount of water that each participating entity must provide, for example, in proportion to their financial contributions or their Lower Basin allocations.

Setting an Example

The MOU contemplates that, in addition to addressing the “acute short-term need” for supplemental storage supplies, information gained under the 500+ Plan may be used to inform “longer term operations.” Because the 500+ Plan focuses on reducing demand for Lake Mead storage water, it could also prove helpful to the Upper Basin as it explores the feasibility of demand management under its 2019 Drought Contingency Plan. Some demand management plans under consideration would compensate water users for forgoing delivery of their water rights, similar to the 500+ Plan.

As a voluntary action focused on reducing water demand, the 500+ Plan represents another important step toward finding collaborative solutions to protect critical water supplies in the Lower Basin. In addition to conserving 1,000,000 acre-feet of water in Lake Mead over the next two years, the 500+ Plan may provide new, valuable lessons for putting state and federal funds to their best use to combat the effects of prolonged drought in the Colorado River Basin.

For further information please contact Daniel McCarl at

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