What the New Colorado River Operating Rules Mean for Southern California

Joe Grindstaff

Oct 2

8 min read

Turquoise river winding through a red-rock canyon under a bright blue sky, with steep cliffs and distant mesas.

The Colorado River is entering a new period of uncertainty.

For decades, the river has supplied water to cities, farms, tribal communities, businesses, and ecosystems across the Southwest. Southern California depends on this water as part of a larger portfolio that also includes State Water Project supplies, groundwater, recycled water, conservation, and other local resources.

However, the amount of water flowing through the Colorado River system has not consistently matched the amount promised under historical agreements.

After years of drought, low runoff, and declining reservoir levels, the rules governing Lake Mead and Lake Powell were scheduled to expire at the end of 2026. The seven Colorado River Basin states spent years attempting to negotiate a replacement, but they did not reach a long-term consensus.

In August 2026, the federal government adopted a new decision framework and temporary operating guidelines for 2027 and 2028.

These new Colorado River operating rules allow the system to continue functioning, but they do not resolve the larger disagreement over how future shortages should be shared.

Why Does the Colorado River Matter to Southern California?

The Colorado River supplies water to seven states: Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming. It also provides water to Mexico under an international treaty.

In Southern California, Colorado River water is transported through the Colorado River Aqueduct and distributed throughout the region by the Metropolitan Water District of Southern California.

This imported water supports communities across Los Angeles, Orange, Riverside, San Bernardino, San Diego, and Ventura counties.

Not every community relies on the Colorado River to the same degree. Some agencies have more groundwater, recycled water, or access to State Water Project supplies than others. Nevertheless, a major reduction in the Colorado River water supply can affect the entire Southern California water system.

If one source becomes less reliable, agencies may need to purchase more water from another source, increase groundwater production, use stored supplies, or accelerate investments in conservation and local water projects.

That is why the future of the Colorado River matters even to customers who do not receive Colorado River water every day.

Why Were New Operating Guidelines Needed?

Several agreements and federal guidelines governing Colorado River operations were scheduled to expire at the end of 2026.

These included the 2007 Interim Guidelines for operating Lake Powell and Lake Mead and determining Lower Basin shortages, as well as the 2019 Drought Contingency Plans.

Those rules were designed to provide structure during drought and declining reservoir conditions. However, the Colorado River system continued to experience conditions more severe than many planners anticipated.

According to the U.S. Bureau of Reclamation, the Basin has experienced an unprecedented drought for 26 years. Following record-low snowpack during the winter of 2025–2026, the combined storage in Lake Mead and Lake Powell fell below levels seen since before Lake Powell began filling in 1963.

Both reservoirs reached record-low elevations in August 2026.

The federal government, Basin states, tribes, water agencies, agricultural organizations, and other interested parties began working toward new post-2026 Colorado River guidelines. Six alternatives were developed and evaluated through the federal environmental review process.

Despite years of negotiations, the seven states did not agree on a long-term operating plan.

What Did the Federal Government Decide?

On August 21, 2026, the Department of the Interior issued a Record of Decision establishing a Colorado River decision framework for 2027 through 2036.

The framework sets the principles, limits, thresholds, and process the federal government will use to develop operating rules through 2036.

However, the actual operating guidelines issued so far apply only to 2027 and 2028.

The federal government expects to issue new guidelines in two-year intervals unless the states and other parties reach an agreement that supports a longer operating period.

This distinction is important.

The federal decision provides a process for managing the river, but it is not the comprehensive long-term agreement many water managers hoped the states would negotiate. It is a way to keep the system operating while discussions continue.

The 2027–2028 Colorado River Operating Guidelines specifically state that they are not intended to represent a long-term operational strategy or establish a precedent for future operations.

How Will Lake Powell Be Managed?

Lake Powell plays a central role in storing Upper Basin water and controlling releases through Glen Canyon Dam to the Lower Basin.

The new guidelines place a strong emphasis on protecting the reservoir elevations needed to operate critical federal infrastructure.

The guidelines initially seek to maintain Lake Powell at or above an elevation of 3,510 feet, creating a buffer above 3,500 feet.

If Lake Powell falls too low, Glen Canyon Dam loses operational flexibility. Hydropower production can also be affected, and releasing water downstream becomes more difficult.

Under the new rules, federal water managers can adjust the amount released from Lake Powell based on reservoir projections. Releases may be reduced when necessary to protect critical elevations.

If Lake Powell is projected to fall below 3,500 feet, the federal government may consult with Basin states, tribes, and other affected parties about additional emergency actions.

These rules recognize a difficult reality: the system cannot continue releasing water according to old expectations if doing so puts the reservoir and dam infrastructure at serious risk.

What Do the New Rules Mean for Lake Mead?

Lake Mead stores water used by the Lower Basin states of Arizona, California, and Nevada, as well as water delivered to Mexico.

For 2027 and 2028, the new guidelines establish a shortage condition for the Lower Basin.

The Lower Basin’s total consumptive-use allocation would be reduced from 7.5 million acre-feet under normal conditions to 6.25 million acre-feet annually.

Under the operating guidelines, the annual reductions would include:

760,000 acre-feet for Arizona
440,000 acre-feet for California
50,000 acre-feet for Nevada

The guidelines also contain additional triggers for consultation if Lake Mead is projected to fall below specific elevations. I personally expect more reductions in the future, however weather is fickle and I remember a time in the early 1980s when Lake Powell had more water than it should have and emergency releases were required.

Protecting Lake Mead is about more than maintaining a visible reservoir level. If the lake falls too low, water deliveries and hydropower generation become increasingly difficult. At extremely low elevations, the infrastructure used to release water may no longer function as it was designed to operate.

The new rules attempt to reduce water use before the system reaches those critical conditions.

Why Could the States Not Reach an Agreement?

The disagreement is not about whether the Colorado River faces a problem. The Basin states generally recognize that current water use must be brought into better balance with the river’s available supply.

The conflict is about how responsibility should be divided.

Upper Basin states include Colorado, New Mexico, Utah, and Wyoming. Lower Basin states include Arizona, California, and Nevada.

Each group views the river through a different legal, geographic, and operational lens.

Upper Basin states argue that their water use is naturally limited by the amount of snow and runoff available each year. During dry years, they may already receive less water because they cannot take water that never reaches their diversion points.

Lower Basin states receive water from major federal reservoirs. Their deliveries have historically been more predictable, even during drought, because stored water can be released from Lake Powell and Lake Mead.

This creates disagreements over whether future reductions should be based on legal entitlements, actual water use, reservoir conditions, percentages, fixed volumes, or a combination of factors.

Agriculture further complicates the negotiations because it uses a large portion of Colorado River water while also supporting food production and local economies. Cities have invested heavily in conservation, but urban populations continue to grow. Tribal water rights and the needs of Mexico must also be included in the broader discussion.

Every proposed solution creates different impacts for different water users and even the current federal decision reducing water to California does not allocate the shortages amongst California water agencies.

What Could This Mean for Southern California?

California’s 440,000-acre-foot reduction does not mean every Southern California customer will immediately receive less water at the tap.

Regional water agencies have stored supplies, local resources, conservation programs, groundwater systems, and access to other imported water sources. The effect will also vary depending on the final agreements and how California manages the reduction among its Colorado River water users.

However, reduced Colorado River supplies can still create long-term consequences.

Potential effects include:

Greater reliance on stored water
Increased demand for State Water Project supplies
Additional pressure on groundwater basins
Higher costs for replacement water
Faster development of recycled water and local supply projects
Greater emphasis on conservation
More competition for limited water during drought
Increased need for regional water transfers and partnerships

California water agencies have already taken steps to conserve Colorado River water and leave additional supplies in Lake Mead. The California Department of Water Resources has documented commitments by California agencies to reduce use and help stabilize reservoir storage.

Those actions can provide short-term benefits, but the Basin still needs a durable agreement that determines how shortages will be shared over the long term.

Why Two-Year Guidelines Are Not a Long-Term Solution

Temporary rules provide necessary certainty for system operations. Water agencies, farmers, power producers, and communities need to know how Lake Mead and Lake Powell will be managed in 2027 and 2028.

But two-year guidelines do not provide enough certainty for investments that take decades to finance and construct.

Water agencies must decide whether to build treatment plants, groundwater storage facilities, recycled water systems, pipelines, and other major infrastructure. Farmers must make long-term decisions about crops, irrigation equipment, and land. Communities need to plan for housing, businesses, and population growth.

Those decisions become more difficult when the future Colorado River allocation may change every two years.

The federal decision framework creates a path for continued operations through 2036, but consensus among the states would provide greater stability.

Without an agreement, federal officials may need to continue making increasingly difficult decisions about shortages and reservoir protection.

Southern California Cannot Depend on One Source

The Colorado River remains an essential part of Southern California’s water supply, but it cannot be treated as unlimited.

The same is true of every major water source.

State Water Project deliveries can be affected by drought, snowpack, environmental regulations, and infrastructure constraints. Groundwater basins must be managed sustainably. Recycled water and desalination require significant investments. Conservation can reduce demand, but it cannot replace every supply needed by a growing region.

Southern California’s strongest approach is a diversified water portfolio that includes:

Colorado River water
State Water Project water
Local groundwater
Groundwater storage and recharge
Recycled water
Conservation and water-use efficiency
Regional water transfers
Desalination where appropriate
Emergency and drought reserves

Diversification allows agencies to respond when one source becomes less reliable. It also reduces the risk that a single drought, infrastructure failure, regulatory decision, or negotiation will disrupt the entire region.

What Should We Watch Next?

The 2027–2028 operating guidelines provide immediate direction, but several important questions remain:

Will the seven Basin states return to negotiations and reach a longer agreement?
How will California implement its share of the Lower Basin reduction?
Will additional conservation be voluntary, compensated, or mandatory?
How will tribal water rights be incorporated into future operations?
What happens if Lake Mead or Lake Powell falls below the elevations anticipated by the guidelines?
Can water agencies create new regional partnerships that reduce pressure on the river?
How will the cost of reduced supplies affect Southern California water rates?

The answers will depend on future hydrology, negotiations, federal decisions, and the investments water agencies make now.

Preparing for a More Limited Colorado River

The new Colorado River operating rules should be understood as a warning and an opportunity.

They are a warning because Lake Mead and Lake Powell have reached historically low levels, and the states have not agreed on a lasting solution.

They are also an opportunity to rethink how the Southwest manages a river that supports tens of millions of people, major agricultural regions, tribal communities, ecosystems, and international obligations.

Southern California has already made progress through conservation, water recycling, storage, groundwater management, and diversified supplies. Those efforts must continue.

The Colorado River will remain important, but future reliability will depend on using less water, sharing shortages fairly, protecting critical infrastructure, and investing in alternatives before an emergency forces the region to act.

The federal government has created rules for the next two years. The much harder task is creating a sustainable agreement for the decades ahead.