As water projects go, Sites Reservoir has always been the Sacramento Valley’s baby – a multibillion-dollar reservoir conceived by Valley farmers, carved out of a ghost town an hour north of the Capitol. Around the Valley, “Build Sites Reservoir” signs dot the roads along mile after mile of orchards and rice fields. But a funny thing has happened as the Sites project, designed as the largest reservoir built in California since the 1970s, pulls together its financing: It’s becoming much less of a Sacramento Valley venture. Over the past two years, scared off by the anticipated costs of storing water there, Valley agricultural irrigation districts have steadily reduced their ownership shares of Sites, giving way to water agencies from Southern California and the San Joaquin Valley.