'This year we need to put our best foot forward,' Gavan added. 'The City expects us to spell out our strategic development.'
Tulchan saw off Brunswick and The Maitland Consultancy to secure the account.
Last month Severn Trent announced the appointment of Novar finance director Mike McKeon as FD.
McKeon's arrival adds the finishing touch to Severn Trent's new management team, led by CEO and former Eircom Networks director Colin Matthews, who took over when Robert Walker retired in February last year.
Matthews has yet to decide whether to spin off Severn Trent's waste business Biffa and its underperforming environmental testing laboratories arm.
Although Severn Trent last month reported an 18 per cent rise in pre-tax profit to £164m, the firm has been on the back foot since water regulator Ofwat referred it to the Serious Fraud Office last November.
Ofwat is concerned about irregularities in the reporting of water leaks at Severn Trent Water, which supplies three million homes with water and sewage services.
Severn Trent has insisted the leaks have no effect upon the integrity of its accounts and believes it has not overcharged customers.