Managed Aquifer Recharge in Practice: California Examples

Comparison table

Santa Clara Valley Water District

Santa Clara Valley, now widely known as Silicon Valley, experienced land sinking in the early 1900s after excessive groundwater removal caused aquifer sediments to compact. This kind of land subsidence can damage infrastructure and reduce long-term aquifer storage.

The Santa Clara Valley Water District was founded in the 1920s to recharge groundwater and prevent further subsidence. Later, imported state and federal water helped restore groundwater levels, and subsidence largely stopped.

Policy lesson: Recharge can protect infrastructure when it is paired with sustained groundwater management, long-term monitoring, and reliable water supplies.

Orange County Water District

Orange County provides an example of coastal aquifer protection, water recycling, and recharge. Saltwater intrusion threatened groundwater in the 1930s, creating a need to protect freshwater aquifers from salty ocean water moving inland.

The district uses injection wells near the coast to help maintain a freshwater barrier and inland spreading grounds to recharge aquifers. It has used Santa Ana River water and highly treated wastewater cleaned to drinking-quality standards.

Policy lesson: Coastal groundwater protection requires more than adding water underground. It depends on recharge, pumping management, water treatment, groundwater monitoring, and careful operations.

Water Replenishment District of Southern California

The Water Replenishment District of Southern California manages groundwater basins that serve millions of residents. Its work connects stormwater management, recycled water, local water supply, and coastal aquifer protection.

The district uses spreading grounds and coastal injection wells to recharge aquifers and help prevent saltwater intrusion. It has invested in water recycling and expanded stormwater capture to reduce reliance on imported water.

Policy lesson: MAR can link multiple policy goals at once: capturing stormwater, using recycled water, improving local supply reliability, and protecting coastal groundwater.

Kern Water Bank

The Kern Water Bank is an example of agricultural water reliability and wet-year/dry-year storage. The southern San Joaquin Valley has high agricultural water needs, but river water supplies can vary greatly from year to year.

The area is geologically suited for underground storage because it is underlain by thick, sandy aquifers. Water can be stored in wet years using spreading grounds and recovered later when needed.

Policy lesson: Aquifer storage can support agricultural reliability, but water rights, ownership, accounting, governance, and recovery rules are central to how the system works.

Cross-cutting lessons for policy staff

• MAR projects should begin with the problem they are trying to solve: drought supply, subsidence, saltwater intrusion, stormwater management, water quality, or a combination of goals.
• Suitable geology is essential, but geology alone is not enough. Projects also need water sources, infrastructure, governance, monitoring, and long-term management.
• Source water matters. River water, stormwater, recycled water, and imported water each have different reliability, quality, legal, and public-communication considerations.
• Recharge method matters. Spreading grounds, recharge basins, stream-channel recharge, and injection wells each fit different aquifers and land-use settings.
• Coastal projects often require coordinated recharge and pumping management to reduce saltwater-intrusion risk.
• Subsidence prevention depends on maintaining groundwater levels before damaging compaction becomes severe.
• Water accounting, monitoring, and public reporting are central to trust and long-term project performance.

Questions for evaluating a MAR proposal

• What problem is the project designed to solve?
• Is the goal water supply, drought resilience, subsidence prevention, saltwater-intrusion protection, stormwater management, water-quality improvement, or another purpose?
• What aquifer will receive the recharge water?
• Is the aquifer suitable for storing and later recovering water?
• What source water will be used?
• How reliable is that source water during wet years, dry years, and drought?
• Are there competing uses or downstream impacts associated with the source water?
• What recharge method will be used: spreading basin, stream-channel recharge, injection well, or a combination?
• What treatment or pretreatment will be required?
• How will water quality be monitored?
• How will groundwater levels be monitored?
• How will the project account for water stored underground and water recovered later?
• Who owns or controls the stored water?
• What rules govern pumping, recovery, and long-term operation?
• What infrastructure will be needed?
• What are the expected maintenance costs and responsibilities?
• How will the project evaluate success?
• How will information be shared with the public and decision-makers?

Concluding idea

The core policy question is not simply “Can we recharge the aquifer?” but “What problem are we trying to solve, what water will be used, where will it go, who will manage it, and how will success be measured?”

Source document

This companion page is based on AGI’s Critical Issues case study:

Managed Aquifer Recharge in California
AGI Critical Issues Program case study describing four managed aquifer recharge examples in California.

Read the full case study PDF