The River Gwash was (and would be) the source of water for the Stamford Canal. Originally a river getting its water from land near Oakham it was dammed and the Rutland Water reservoir was created. The present River Gwash is just the run-off from the reservoir so is under permanent control. An ideal source of water for a canal!
The thing that made the Stamford Canal work was a sequence of sluices and weirs where the canal wanted to cross the route of the river at Newstead. The remains of those devices are still in situ and would need the minimum of work to excavate, clean and reinstate to their original function.