California officials are slowing the release of water from a lake behind the nation's tallest dam so crews can remove debris from the bottom of the structure's damaged spillway.

State Department of Water Resources officials said Thursday that removing debris protects Oroville Dam's power plant and will allow for it eventually to be restarted.

Officials had been releasing 100,000 cubic feet of water, or enough to fill an Olympic-size swimming pool, each second from the lake since Sunday, when the sheriff ordered an immediate evacuation. They didn't say how much water is now being released.

Department acting Director Bill Croyle said Wednesday that water managers would start dialing back the flow now that the lake has been reduced and can absorb runoff from storms expected over the next several days.

California officials say the water level at Lake Oroville is 32 feet below its dam's damaged emergency spillway. For a third day, DWR officials said dump trucks and helicopters are dropping thousands of tons of rocks and sandbags to shore up the spillway at the nation's tallest. Barges and cranes are also being mobilized to remove debris and sediment from a diversion pool.

Officials also say they're confident the damaged spillway and eroded hillside can withstand approaching storms. Weather forecasts call for 2 to 4 inches of rain and snow in the foothills and mountains near the dam. But the storm is expected to drop less rain and create less runoff than storms from last week.

Croyle said Thursday that officials identified three areas where erosion caused the most concern about potential flooding.

He says one area has been 100 percent repaired, while the others were 25 percent and 69 percent fixed.

Croyle says officials are reducing the amount of water released from the lake, but he still expects the level to continue falling through the duration of storms forecast in the coming days.

With less water flowing down the dam's spillway, officials hope to clear debris that threatens a hydroelectric power plant at the base of the dam.