A ruling by a federal judge that cut by two-thirds the amount of water flowing from the Sacramento-San Joaquin delta to Southern California - combined with a lingering drought - has set off a chain reaction that could result in higher water rates in parts of San Bernardino County.

The Metropolitan Water District of Southern California, a regional water supplier based in Los Angeles, adopted a plan Tuesday that would penalize client water agencies exceeding their allocation, a cost that could be passed on to ratepayers.

One of the MWD's 26 clients is the Inland Empire Utilities Agency, which relies on Metropolitan for roughly one-third of its water supply.

The Inland Empire agency serves 800,000 customers in seven cities - Chino, Chino Hills, Fontana, Montclair, Ontario, Rancho Cucamonga and Upland.

"The first thing to understand is they're going to apply very significant rate increases and penalties if we use water above what we're allocated," said Wyatt Troxel, inland water board president.

Troxel estimated water rates could increase from 3percent to 5percent in the short term and predicted that cities experiencing rapid population growth could be hit hardest. Programs to provide recycled water to municipalities should decrease the demand for imported water in the long term, he said.

Montclair, Upland and Rancho Cucamonga have the greatest risk because Montclair and Upland are still in the process of implementing a recycled

water program and Rancho Cucamonga is continuing to develop, he said.

Fontana Water Co., which will begin processing inland agency water this summer, doesn't expect its rates to be affected by the recently adopted plan, said Assistant General Manager Robert Young.

Fontana Water Co. is a unit of San Gabriel Valley Water Co.

Penalties could be imposed as early as July, although it is unlikely that allocations will be exceeded so quickly following this winter's rains, said Jeff Kightlinger, MWD general manager.

In addition, the MWD will consider adopting a general rate increase in March, Kightlinger said.