The nation's oldest operating nuclear plant has reduced its power after unusually low tides and high winds impacted the water levels in its intake canal.

Oyster Creek declared an unusual event around 5:25 a.m. Saturday. That's the lowest of four emergency classification levels used by the Nuclear Regulatory Commission.

Although water levels later returned to normal, plant officials say the unusual event declaration will remain in place until operators confirm the environmental anomaly won't recur with the next tidal change.

A plant spokeswoman says minimum water levels were established "as one of many conservative measures" to ensure that operators have access to multiple and redundant sources of cooling water should the plant need to be shut down quickly.

Oyster Creek is located in Lacey Township, about 60 miles (96 km) east of Philadelphia.