By Evan Halper

The long-range weather forecast is the biggest wild card in the battle over every available bucket of water in drought-stricken California _ but a close second may be Dianne Feinstein.

In a dispute in which positions have hardened after years of fighting, the state's senior U.S. senator, who is expected to broker any deal that reallocates water supply, is one of the few remaining enigmas. The only thing consistent about Feinstein's role as water referee is that the fights have left bruises on the exacting and thick-skinned senator over the years. The past few weeks have been particularly rough.

A year that started with Central Valley figures branding her a radical environmentalist and Bay Area dilettante ended with accusations from once-friendly colleagues and liberal editorial boards that the 22-year veteran of the Senate was shilling for Big Agriculture.

For months, Feinstein had tried to put together a compromise drought-relief bill by negotiating a water deal privately doors with the state's major agricultural interests. Late in Congress' lame-duck session, those talks collapsed. No legislation was passed.

Yet Feinstein is eager to get back in the ring as soon as Congress returns in January.

"We can't wait for more rain, we need to be able to do more with what we have," she said in an email.

Even when Republicans take over the Senate next year, Feinstein will probably remain the chamber's arbiter of California water. Long-standing tradition in the Senate is not to mess with water policy in a state without the support of at least one of its senators.

One key factor will be Feinstein's ability _ and willingness _ to maintain a careful balance between agriculture and the state's numerous and vocal environmental activists.

Over the years, Feinstein has mastered an ability to stay on good terms with both groups. She has a nearly perfect legislative score from the League of Conservation Voters, balanced by radiant endorsements from the Western Growers Association.

The senator's deep connection with agricultural leaders, who traditionally lean Republican, has long had advantages. They dominate politics in key inland regions and have helped her coast to re-election over and again. In contrast, Western Growers has worked aggressively _ albeit unsuccessfully _ to unseat California's other senator, Democrat Barbara Boxer.

In addition to having relationships on both sides, Feinstein knows the details of water policy like no other elected official in Washington. She has presided over most significant California water negotiations in Congress for years, aggressively boring into the minutiae that other lawmakers eagerly shove off to staff.

A growing number of environmental groups and their allies in the House take the view that Congress should simply stay out of the state's water allocation issues. They worry that any increase in pumping leaves the fragile ecosystem of the Sacramento-San Joaquin River Delta vulnerable to collapse and say they have the support they need in the courts and the Legislature to enforce a solution that would not involve diverting additional water to large Central Valley farms.

That resistance to a federal solution led to Feinstein's cutting the environmental groups out of her negotiations. But the groups proved a more troublesome foil than anticipated, using social media and the 24-hour news cycle to attack the senator as she tried to bring her negotiations with growers to a close.

"Things played out very differently this year than they had in the past," said Doug Obegi, an attorney at the Natural Resources Defense Council.

The last time Feinstein insisted on diverting more water to growers over the objections of environmentalists, "she locked everyone in the room, which she is famous for, and we were successful at convincing her we could reach a compromise," he said. "We never got that call this year."

(c)2014 Los Angeles Times