Petition Policing Riots

I believe that the Police should have use of Water Cannons to deal with Civil Disturbances. Such as the recent Student Fees protests, G8 protests and this weekends riots and looting.
The water cannons should be filled with an indelible dye. Those people causing / attending the disturbance can be sprayed with the dye thus allowing the police to pick them up after the event. Combined with the use of video evidence people can be either eliminated from the investigation or prosecuted.
I believe that this will reduce the number of people willing to partake in these disturbances and reduce the number of injuries to police officers. And will contribute to a safer place to live