Members of the CwM team were fortunate to attend the 11th edition of the International Symposium on Managed Aquifer Recharge (ISMAR) this month. The event is organized by the International Association of Hydrogeologists, UNESCO, and the American Society of Civil Engineers and has previously been held in locations from Adelaide to Beijing, Madrid, and Abu Dhabi, among others. This year’s conference was held in Long Beach, California and had a heavy emphasis on water issues in the Western US and similar semi-arid regions.
ISMAR is a highly focused event intended to improve research, communication, and implementation of engineered Managed Aquifer Recharge (MAR) across the globe. This year’s event included attendants from six continents with presentations on Aquifer Storage and Recovery (ASR) case studies and technological advancements, application of surface infiltration methods, biogeochemical processes related to MAR, geophysical and remote sensing technologies, and societal and governmental frameworks for expanding MAR for various purposes. Ongoing research on and practical applications of MAR are not only for groundwater level recovery, but also for improvements of groundwater quality, preventing seawater intrusion in coastal areas, and enhancing climate resilience.
Among the highlights of ISMAR 11 was a field trip around the Orange County Water District (OCWD) to view their water source management, MAR, and water recycling systems. OCWD provides high-quality drinking water to more than 2.5 million people in the Los Angeles-Anaheim area and manages the Orange County Groundwater Basin. The largest natural source of water to the District is the Santa Ana River which flows from the San Bernardino Mountains to the northeast. In east Anaheim, OCWD has developed a system of levees and adjustable dams which divert excess flows from the river into recharge channels. These channels are maintained and managed to keep infiltration rates as high as possible. In some cases, up to 100 cfs (44,880 gpm) can be diverted and recharged through the Santa Ana River recharge channels. The diversions are placed such that the recharged water is able to flow through the Shallow Aquifer and into the deeper Principal Aquifer in the basin, which is the primary groundwater source for the area. The channels also provide wildlife habitat and opportunities for recreation.
A rubber dam diverts up to 100 cfs (about 35 cfs in this photo) from the Santa Ana River into a parallel recharge channel.
OCWD utilizes other sources of water, including precipitation, imported water from the California Aqueduct and Colorado River, and recycled wastewater. These sources of water are used for more dispersed recharge through about a dozen infiltration basins throughout the Anaheim area. These basins range from just a few feet to over 50 ft in depth and area each operated in a manner optimized to that basin. The highest performing basin is the La Palma Basin, which can infiltrate about 10 ft of water per day. At this level of infiltration, the basin can recharge about 85 cfs (38,150 gpm) continuously. The recycled water used to fill the basin is so clean that infiltration can continue at this rate for a year before maintenance is necessary.
The La Palma Recharge Basin in Anaheim recharges about 85 cfs of high-quality recycled water 24-7 and is one of many recharge basins distributed across the City.
Much of the water used for the groundwater recharge basins comes from OCWD’s Groundwater Replenishment System (GWRS). The GWRS is the largest wastewater reuse and recycling system in the world and allows OCWD to manage the arid, highly-populated Orange County Groundwater Basin sustainably. Up to 100 million gallons per day of secondary wastewater can be delivered to GWRS each day from the sanitation district. The water passes through three main phases (microfiltration, reverse osmosis, and UV treatment) before becoming high-quality drinking water, which is then used for recharge through the infiltration basins or for the OCWD seawater barrier injection wells.
Raw water microfiltration basins at the OCWD Groundwater Replenishment System. About a dozen basins, each with four Memcor filter tubes (right) receive raw water from the Orange County Sanitation District. Each filter tube can process about 2 million gallons per day, removing particulate larger than 0.2 microns.
Inside of the Groundwater Replenishment System’s Reverse Osmosis Building. Over 100 million gallons of water per day is purified through about 2,500 RO chambers, which remove almost all dissolved constituents larger than a water molecule. The group is being shown the RO membrane that is contained within each chamber.
The last stage of treatment is UV sterilization. The 100 million gallons per day passes through large-diameter pipelines filled with UV light tubes, which provide about 10 seconds of high-intensity UV contact time for the process is complete. In addition to killing any biological components in the water, the UV process breaks down chemical residues from the RO process.
The end product of microfiltration, reverse osmosis, and UV sanitation of recycled wastewater is high-quality drinking water. This water is used to recharge thousands of acre-feet of groundwater in the Los Angeles Basin each year to maintain aquifer sustainability, improve groundwater quality, and prevent saltwater intrusion.