The Environmental Protection Agency has begun an investigation into whether California’s top water agency has discriminated against Native tribes and people of color, carrying out a civil rights probe that could force changes in how the state manages water. The EPA’s civil rights office announced it has accepted a complaint filed by tribes and environmental justice groups, who accuse the State Water Resources Control Board of discriminatory practices and mismanagement contributing to the ecological deterioration of the Sacramento-San Joaquin River Delta. The tribes and environmental groups argue that out-of-date water quality standards in the Delta have led to collapsing fish populations and worsening toxic algae blooms, harming tribes whose traditions are tied to the rivers and leaving residents in South Stockton and other areas with stagnant waterways often choked with algae.