Retired Court of Appeal Judge Lyn Stevens QC has been appointed to head the independent inquiry into the Havelock North water contamination crisis.

Attorney-General Chris Finlayson has announced the appointment, also naming former director-general of health Karen Poutasi and engineering expert Anthony Wilson as panel members.

The contamination led to more than 4000 people being infected with a gastro bug, school closures and the need to boil drinking water.

The terms of reference for the inquiry are:

* How the Havelock North water supply system became contaminated
* How this was subsequently addressed
* How local and central government agencies responded to the public health outbreak that occurred as a result of the contamination
* How to reduce the risk of outbreaks of this nature recurring.

The inquiry panel will begin its work this week and report to Mr Finlayson by March 31 next year.