The Cumbria River is a river located in the county of Cumbria, England. It is the longest river in the county and is approximately 70 miles long. The river's source is located in the Lake District and it flows through the EDEN Valley before emptying into the Irish Sea. The river's name is derived from the Celtic word for 'deep valley'. The answer to the crossword puzzle is EDEN, which is the name of the valley that the river flows through.