Banking Water for California's Future: California Needs Both New Reservoirs and Groundwater Storage

California's water future depends on maximizing every storage opportunity available - both above and below ground. While recent decades have focused on groundwater solutions alone, the reality is that California needs a comprehensive approach that includes both new reservoirs and expanded groundwater storage.

The Case for Both Solutions

Recent atmospheric rivers highlighted a critical reality: California lacks sufficient capacity to capture excess water in wet years. Despite record rainfall, millions of acre-feet of water flowed to the ocean because we lacked adequate storage infrastructure. This lost opportunity could have supplied farms and cities for years.

New Reservoir Projects

Several promising reservoir projects could significantly expand California's surface storage:

Sites Reservoir: This proposed off-stream reservoir west of the Sacramento Valley could store 1.5 million acre-feet of water - enough to supply 3 million households annually. By capturing excess flows during wet periods, Sites could provide vital flexibility during droughts without damming additional rivers.

Temperance Flat: Located above Millerton Lake, this project could add 1.3 million acre-feet of storage, helping to capture high-flow events from the San Joaquin River while providing critical flexibility for both farms and environmental needs.

Los Vaqueros Expansion: Expanding this existing reservoir would add 115,000 acre-feet of storage while improving water quality and reliability for Bay Area communities.

Groundwater Storage Innovation

Simultaneously, California should aggressively expand groundwater storage through:

Groundwater Recharge Basins: Large-scale recharge facilities like the Kern Water Bank have proven highly effective at capturing excess flows. Building more such facilities throughout the Valley could add millions of acre-feet of storage capacity.

Flood-Managed Aquifer Recharge (Flood-MAR): Using flood waters to recharge aquifers offers dual benefits of flood protection and water storage. Early projects show enormous potential for capturing high-flow events.

On-Farm Recharge: Converting farmland to double as recharge basins during wet periods provides a cost-effective way to expand storage while maintaining agricultural production.

Why We Need Both

Surface and groundwater storage complement each other:

Speed of Access: Reservoirs can quickly release water when needed, while groundwater provides longer-term drought insurance.

Flood Control: New reservoirs offer immediate flood protection benefits that groundwater storage alone cannot provide.

Environmental Flows: Surface storage provides more flexibility to manage water releases for environmental needs.

Groundwater Recovery: Having adequate surface storage helps ensure enough water is available to recharge overdrafted aquifers.

Economic Considerations

While new reservoirs have higher upfront costs, they offer unique benefits:

• Immediate flood control

• Hydroelectric power generation

• Recreation opportunities

• Precise flow management for environmental needs

Groundwater storage provides:

• Lower cost per acre-foot stored

• Minimal environmental impact

• Reduced evaporation losses

• Flexible, scalable implementation

Moving Forward

California needs a comprehensive strategy that includes:

1. Expedited permitting for both surface and groundwater storage projects

2. Public-private partnerships to fund new infrastructure

3. Coordinated operation of surface and groundwater facilities

4. Updated water rights framework to facilitate storage projects

The Time to Act

California faces increasing weather extremes - shifting between intense floods and severe droughts. Maximizing storage capacity both above and below ground is essential for:

• Capturing flood flows

• Protecting communities

• Ensuring agricultural sustainability

• Meeting environmental needs

• Providing urban water security

The next major drought will come. The only question is whether we'll have built enough storage capacity - both surface and groundwater - to sustain California's communities, farms, and environment through it. We can't afford to pick just one solution. California needs both new reservoirs and expanded groundwater storage to secure its water future.