The Nebraska Public Power District is draining canals from the Keystone Dam to Lake Maloney as part of regular maintenance on the western Nebraska waterway.
Officials say the utility has started draining the canals so workers can make detailed inspections and maintenance as required every five years.
Utility water resources adviser Edward Dekleva says crews will inspect the bottom and sides of the canals.
They also will check structures that normally are underwater.
Water levels at Lake Maloney also are expected to drop.