Water is critical to California’s economic development, supporting environmental preservation as well as extensive agricultural, industrial, and recreational activities. The high demand for water, particularly in the hot summer months when prolonged droughts and water shortages are common, is fueling growing conflict between different user groups and regions over water availability. 

El California Water Plan 2023 promotes this vision: “All Californians benefit from water resources that are sustainable, resilient to climate change, and managed to achieve shared values and connections to our communities and the environment.” To achieve the ambitious goals outlined in the California Water Plan, the state has started implementing innovative technologies to manage resources more efficiently in urban and agricultural settings. These water treatment solutions are discussed in more detail below.

Desalination

While California may have limited fresh water, its coastline stretches for 840 miles (1350 kilometers) along the Pacific Ocean, providing ready access to seawater. California also has extensive brackish groundwater, which offers a feasible alternative water supply to inland regions. So desalination has emerged as a way to address California’s water challenges. 

Desalination plants use advanced membrane filtration technologies like reverse osmosis to remove salt from seawater and brackish water, providing a reliable and sustainable source of water independent of rainfall and surface water availability. This helps mitigate water scarcity and build climate resilience, providing water security to urban areas and agriculture.

Water Reuse

Membrane bioreactor (MBR) systems are playing a significant role in California by revolutionizing wastewater treatment. MBR systems integrate biological treatment with membrane filtration, producing high-quality effluent that meets or exceeds stringent regulatory requirements for reuse. Reclaimed water from MBR systems can be used for crop irrigation, landscaping, industrial processes, and groundwater recharge. This reduces reliance on freshwater sources, particularly during droughts, and helps conserve precious resources. 

Once treated, the recycled water is distributed through systems often referred to as purple pipe systems because of the distinctive color of the pipes used. Purple pipe systems provide a consistent source of water for irrigation, helping to sustain agricultural productivity even during dry periods. This reduces the economic impact of water shortages on farmers and supports food production.

By promoting water reuse, MBR technologies supported by purple pipe systems help reduce the environmental footprint associated with freshwater extraction and wastewater disposal, while also supporting California’s efforts to achieve water resilience and mitigate the impacts of climate change. This is crucial in a state like California, where water demand often exceeds natural supply.

Investing in recycled water infrastructure and purple pipe systems offers long-term economic benefits. It reduces the need for costly new water supply projects and expands the effective use of existing wastewater treatment facilities, promoting the efficient use of resources while enhancing water resilience.

Groundwater Recharge

Groundwater typically accounts for around 40% of California’s total freshwater supply, and in dry years, this can increase to 60% or more, serving as a buffer when surface water is scarce. In California, groundwater recharge is a key strategy. Managed Aquifer Recharge (MAR) involves replenishing groundwater with sources such as treated wastewater, stormwater, or floodwater (Flood-MAR). There are various ways to achieve this: 

• Green infrastructure: Features such as permeable pavements, rain gardens, and bioswales can be incorporated into landscaping to capture and recharge aquifers with rainwater. 
• Infiltration basins: Water can be channeled to surface basins, where it is allowed to percolate through the soil to recharge aquifers.
• Injection wells: Surface water and treated wastewater can be injected directly into wells to replenish aquifers.
• Spreading grounds: Water can be spread over land to enhance natural infiltration. For example, agricultural landowners can divert floodwater to flood plains or detention and recharge areas. 
• Riverbank filtration: Natural riverbanks can filter and recharge aquifers.

Building Water Resilience

By replenishing aquifers with surface water or treated wastewater, MAR enhances water security and builds drought resilience by providing a dependable source of water that can be accessed during periods of low precipitation. The use of treated wastewater for groundwater recharge aligns with sustainable management practices and promotes a circular water economy, reducing the demand for freshwater supplies and supporting the efficient use of available resources. 

By implementing a range of innovative solutions, California is steadily enhancing its water security, building climate resilience, and ensuring a sustainable water future for farmers, industries, and residents across the state.