Garda chiefs will operate a “low-profile” presence involving uniformed members, but will have at least one public order unit on standby in case any fringe group threatens to spoil the event.
Security bosses are most concerned that militant republicans — numbering up to 70 or so people — may try to orchestrate confrontations with gardaí.
“We know that republican groups are coming out to play,” said one security source.
Right2Water organisers said they were “mystified” at the rumoured security concerns and said the last two major protests, which they say attracted more than 300,000 people in total, occurred without incident.
One garda source said the incident last month in which Tánaiste Joan Burton was trapped in her car for two hours by protesters had highlighted the risks posed by “light policing”.
He said between 250 to 300 gardaí would be on duty tomorrow, including at least one public order unit, comprising 25 members. This unit will be kept on standby, away from the crowd.
Separately, British comedian Russell Brand called on Irish people to “bunk work Wednesday” to join the protest.
In an interview with Right2Water founder Brendan Ogle of the Unite union, Brand urged people not to go to work and to “take the day off, because, you know, big corporations, they’re doing you over at every opportunity not paying their taxes”. He urged English and Scottish people to “take a little ferry trip or a plane ride” to support the protest.
Brand added: “The Irish people fought to kick the British out of your country. Now your own government are ripping you off over water.”