Do We Really Need Water Cannon

The ACPO request for water cannon strikes me as more a bureaucrat led demand for money in the manner of the suggested national ID card scheme.  Three possible uses in a decade sounds pretty flimsy usage for such big and I presume expensive equipment.  I also multiple vehicles would have to be deployed in different parts of the country so that they could be called up for supposed need.  It also seems that technology has outpaced this solution.  The student protests in 2011 came together and dispersed far too quickly for water cannon to have been effectively brought to bear.