It involves reprofiling an embankment but care will be taken not to disturb otters in the area.
The Canal and River Trust has applied to Pendle Council for planning permission for the works at Barrowford Reservoir after a 2017 safety inspection.
They involve the re-profiling and stabilisation of the embankment to allow the water level to be reduced.
A Design and Access Statement with the application say: "The reservoir is believed to have been constructed circa 1885.
"This document seeks planning permission for the re-profiling and stabilisation of the downstream reservoir embankment to allow a reduced water level at Barrowford Reservoir, Colne Road.