Originally, the Warwick and Birmingham Canal, which in 1927 was combined with several other canals and updated with wider locks to provide quicker access to London from Birmingham.
The main line of the Grand Union is considered to terminate at Bordesley Junction. From here, there are two routes, both part of the Grand Union Canal. The original line of the Warwick and Birmingham Canal leads to the Digbeth Branch Canal of the Birmingham Canal Navigations at the Warwick Bar. While the later line of the Birmingham and Warwick Junction Canal leads to the Birmingham and Fazeley Canal (and Tame Valley Canal) at Salford Junction, which in turn has connections to the Coventry Canal and the Trent and Mersey Canal. (info from Wikipedia)