Councilman Hal Bernson asked the City Council on Wednesday to consider redesigning the Chatsworth Reservoir, which has been drained for more than 20 years as seismically unsafe, so it will fill with runoff from future rainstorms as a drought-fighting measure.

Environmentalists reacted with concern, expressing fears for the wildlife refuge that now occupies the site.

Bernson's request, which bypasses the usual committee process and is scheduled to be voted on by the council next week, would instruct the city Department of Water and Power to study the feasibility of repairing Chatsworth Reservoir and "declare a priority for filling the reservoir with storm water."

Although recent rains and flooding "may have appeared to bring the city up to normal rainfall amounts, the city is still in a state of emergency in regard to insufficient water supplies due to drought conditions," Bernson said in his motion.

"Unfortunately, the city has no means to capture and use most of the rainwater which falls over Los Angeles."

The 580-acre reservoir was drained in 1969 for repairs. After the 1971 Sylmar earthquake, it was determined that the dams on either end were seismically unsafe, that repair would be costly and that the reservoir itself was outmoded, said DWP spokesman Ed Freudenberg.

"We have no idea how long it would take to repair. . . . We also want to see what the cost factor is," said Bernson aide Ali Sar.

The reservoir and surrounding area has since become a 1,320-acre wildlife refuge, populated by a variety of birds and animals and maintained by the department with the help of volunteers from environmental groups. The area is a major West Coast resting place for Canada geese on their annual migration and home to thousands of the geese that winter in the Valley each year.

The area has also been frequently used as a movie location.

Repair of the dams was given a low priority after the department decided instead to construct several storage tanks in the western San Fernando Valley in the 1970s, Freudenberg said.

"There were storage tanks placed in the west end, which alleviated the need for emergency storage in that area," he said. "We found out that our system could operate without" the reservoir.

The department has not studied the matter in recent years, Freudenberg said, but he suspects that repairing the dams and redesigning the reservoir to hold storm runoff would be very difficult.