The San Diego County Water Authority announced Thursday it has extended through 2047 a historic agreement to secure independent water supplies from the Colorado River. The water authority’s board voted unanimously to extend the agreement with the Metropolitan Water District to transport 2 million acre-feet of Colorado River water between 2037 and 2047. Water transferred under the agreement represented 20 percent of San Diego’s needs in 2017. The complex agreement covers water originally intended for Imperial Valley farms and requires the Los Angeles-based Metropolitan Water District to transport that water to San Diego via the Colorado River Aqueduct.