The River Blackwater is a small tributory of the River Shannon. The catchment area covers 15,500 acres in County Clare with the village of Clonlara at the centre. Most of the area is steeply sloped; therefore the river responds extremely quickly to rainstorms.
In the late 18th and early 19th centuries works were carried out to improve navigation on the lower Shannon. This included the construction of the Plassy/Errina Canal and the diversion of the Blackwater River for part of its course. The works also included the construction of embankments along the canal and along the River Blackwater.
The jurisdiction of the Commissioners of Public Works extends to the diversion point of the Blackwater River below Mount Catherine Bridge. The condition of the embanked sections and the canal bank which drains within the Commissioners jurisdiction is subject to continuous periodic examination and remedial maintenance work is carried out as necessary.