Construction of the "Dry Canal" as the Cong Canal has come to be known, commenced in 1848. Work continued for 6 years when the decision to abandon the work, except for that necessary to allow the channel to serve for drainage purposes, was taken.
According to Delany (A Celebration of 250 Years of Ireland's Inland Waterways - Appletree press 1992), the reasons for its abandonment were:
The canal today contains water depending on the time of year and weather factors. The photographs on this site show the canal, both in water and in its dry state.
North of Cong at Creggaree, the canal is diverted into an adjacent stream and the bed remains dry from this point to Lough Corrib. The section south of Cong was sold to Lord Ardilaun, becoming part of the Ashford Castle estate and one of the locks converted to a boathouse.
In Cong itself, it is possible to walk into the dry lock and harbour.
The best source of information on the canal that I have come across is a chapter in the book "By The Corribside" by Maurice Semple. The second edition of this work was published in 1984 by the author.