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,=:> I-' co 0) Salinity Impacts In Southern California Salinity has always been a concern of water resource managers in Southern California. When salinity concentrations of imported water are reduced, the region benefits from improved use of ' local groundwater and recycled water and reduced costs to water consumers and utilities. Metropolitan estimates that $95 million of economic benefits would result annually if the Colorado River Aqueduct and State project waters were to simultaneously experience a 100 milligram per liter reduction in salt cOntent from their historic average. Conversely, about the same dollar amount of impacts would result if imported water salinity increased by 100 milligrams per liter. Recently, Metropolitan conducted a Salinity Management Study (Study) in close collaboration with its member agencies and numerous other concerned agencies including the U. S. Bureau of Reclamation. The Study identities the impacts of salinity on the coastal plain of Southern California and recommends a long term strategy and action plan. About half of the region's salt is contnouted by imported water, and the other half comes from local sources. Colorado River water constitutes Metropolitan's highest source of salinity, varying from 535 to 734 milligrams per liter since 1972. Hardness comprises about one-half of the Colorado River Aqueduct salt load and causes troublesome scaling problems to indoor plumbing appliances and equipment in homes, businesses and industries. The State project provides Metropolitan with lower salinity water, which can be used to blend down Colorado River Aqueduct concentrations. State project salinity levels can change rapidly in response to hydrologic conditions, and such changes are noticeable and disruptive as compared to the very gradual, almost imperceptible changes that occur in local streams, groundwater and wastewater collection systems. A CALFED Bay-Delta solution could lower State project salinity by 100 milligrams per liter and reduce its short-term variability. Local salinity sources include naturally occurring salts, salts added by urban water users, infiltration of brackish groundwater into sewers, irrigated agriculture, and confined animal waste management practices. Urban use salt contributions to wastewater range from 250 to 400 milligrams per liter or more in some locations. Metropolitan's Action Plan Metropolitan's Board of Directors adopted a salinity management policy and corresponding Action Plan in April 1999 . Metropolitan is committed to the following long-term policy to control salinity: . Protect Metropolitan's imported source supplies from additional salinity, and where feas:ible seek reductions. . Achieve, to the extent reasonable and practical, a total dissolved solids concentration objective of 500 milligrams per liter in Metropolitan's distribution system. 22