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GEO-6 Regional Assessment for North America


impurities. This association allows the new plant to share the power station’s water lines, which reduces its cost and its impact on marine life (Little 2015). Built in collaboration with the San Diego County Water Authority and Poseidon, a private developer of water infrastructure, the plant is in the early stages of startup. Nearly a tenth of the San Diego County’s total water supply will come from this facility. A hundred million gallons of ocean water will be pumped through the plant daily; half will become drinking water, the other half will flow back into the ocean as brine, carrying the removed salt. Poseidon is planning to build another fifty- million-gallon-per-day


desalination plant in Huntington


Beach, which will supply the Los Angeles area. Fourteen other mid- and large-scale plants have been proposed along the state’s coast. A plant in Santa Barbara, California, which had been unused for more than two decades, is planned to be refurbished and opened. The reason it had not been used initially is that the drought that prompted its construction ended and the water shortage abated. The question remains whether the current drought will end and make the Carlsbad plant unnecessary, or if the current drought it associated with worsening climate change (Little 2015).


Most new plants, including Carlsbad, use reverse osmosis, which removes salt and requires enormous pressure to push the saltwater through the filter (National Research Council 2008).


There is some opposition to desalination, based in part on its huge energy demands. However, advances in reverse- osmosis technology have cut the amount of energy used in desalination by about half in the past two decades. In addition, almost all of the freshwater used by the twenty-two million people of Southern California is imported, much of it pumped long distances from Northern California, which also requires significant energy. Southern California also obtains freshwater from the Colorado River, the waterway that supplies six other US states and Mexico. Additional environ- mental concerns involve impingement and entrainment of marine organisms into the inflow, but since the Carlsbad plant is co-located with an existing power plant, additional


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impacts are minimized. At the other end, the salt extracted from seawater forms a heavy brine that is pumped back into the ocean, and can affect physiology, development, and behaviour of marine organisms, potentially destabilizing the ecology around the outflows (Jenkins et al. 2012). Although the brine is sprayed in an upward direction, since it is denser than water, most of it settles onto the bottom, affecting benthic organisms.


Water re-use


Through the natural water cycle, the earth continually reuses water. More recently people have used technology to speed up natural processes. Increasingly, communities are exploring ways to beneficially reuse water before it is put back into the natural water cycle. Reused water is most commonly used for nonpotable purposes, such as agriculture, landscape, and park irrigation. Other uses include cooling water for power plants, industrial process water, and to enhance natural or artificial lakes and wetlands. Some projects use recycled water indirectly for potable purposes such as recharging ground water aquifers and augmenting surface water reservoirs with recycled water (EPA 2016c). Such uses become more urgent during droughts. In addition to providing a dependable, locally controlled water supply, water reuse can provide other environmental benefits by decreasing the diversion of water from sensitive ecosystems, reducing wastewater discharges, and reducing pollution. However, in water systems that have over allocated water rights, water reuse can sometimes result in reduced in-stream flows (Sacbee 2016).


Groundwater governance


Groundwater governance in North America is decentralized and highly variable. In the US, state reliance on groundwater ranges from about 5 per cent of withdrawals (West Virginia, Virginia, Connecticut, Montana) to 95 per cent (Hawaii), with western states generally relying more heavily on groundwater (Megdal et al. 2015).


There are also great variations in


legal frameworks related to, for example, the recognition of connectivity between surface and groundwaters, and


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