Executive Leadership Team

Chief Executive

Michael Brewster

Michael Brewster is a senior infrastructure leader with extensive experience across Tasmania’s energy and water sectors and New Zealand’s water reform programme. He served as the inaugural Chief Executive Officer of TasWater, guiding the organisation through major transformation and strengthening its focus on safety, customer service, and environmental outcomes.

In 2023, Michael joined New Zealand’s Department of Internal Affairs as Chief Executive of the proposed South Island water services organisation ‘Entity D.’ Working with Ngāi Tahu, councils, and DIA teams, he helped shape the design and establishment plans for the new entity, gaining valuable insights into the opportunities and complexities of water sector reform in New Zealand.

Michael has held a range of senior executive roles in the electricity and engineering consulting sectors, including leading Tasmania’s Electricity Reform Business Transition Group. He has also contributed to public sector governance as a State Planning Commissioner and lectured in project management. He is a past Fellow of the Institution of Engineers, a Chartered Engineer (Electrical), and former President of Engineers Australia, Tasmania Division.

Chief Corporate Services Officer 

Ian Georgeson

Ian is responsible for providing effective corporate services across Tiaki Wai. His team covers health and safety, people and capability, digital products and services, commercial and procurement, business planning and transformation.

Ian has over 35 years' experience as a finance professional. Prior to joining Tiaki Wai in April 2026, Ian was CFO at Kapiti Coast District Council for around five years, and prior to that spent 20 years in central government - mainly Police and the Ministry of Social Development. 

Chief Customer Officer

Liza Gunn

Liza leads our customer-focused functions, including customer care, faults and resolutions teams, communications and stakeholder engagement, the billing team, channels, strategic customer relationships and customer research. 

Liza has over 15 years’ experience leading large-scale customer, digital and service transformation while also leading large customer operations teams.  

Before joining Tiaki Wai in July 2026, Liza was General Manager Customer Service and Continuous Improvement and acting General Manager Digital at New Zealand Post. 

Chief Financial Officer 

Dave Humm

Dave leads our financial team, which is responsible for financial strategy, financial controls, funding and treasury arrangements, pricing and revenue frameworks, and financial reporting.

Dave is a senior finance leader, with a career spanning over thirty years and across a range of sectors. He led the finance and funding workstream for the establishment of Tiaki Wai and was previously GM Corporate Services/Chief Financial Officer at Greater Wellington Regional Council. 

Chief Operating Officer

Charles Barker

Charles is responsible for the operational delivery of a reliable and efficient three waters network that meets the needs of our client councils and stakeholders. This includes maintenance and development of water infrastructure, ensuring high-quality service delivery, asset resilience, and delivery of short to medium term goals that align with long-term strategic goals.

Charles has over 25 years' experience in regulation and operations. 

Qualifications

• Bachelor of Arts (Hons), Political Science (Canterbury)

• Masters in Strategy (Victoria University)

Chief Risk and Compliance Officer (Acting)

Erin Ganley

Erin is responsible for providing assurance that Wellington Water's operation and maintenance of the three waters networks is compliant with legislation and regulatory standards. Her team covers legal, risk, assurance, compliance and further supports the company by providing support in emergency management and business continuity. Erin’s group is unique in the fact that it works across the company to provide assurance to the Chief Executive and Board of Directors.

Erin has over 20 years' experience in the water industry across risk, assurance, compliance, asset management and operations. Prior to joining Wellington Water in September 2014, Erin worked in roles within the local government and the consultancy sector.

Qualifications

• Bachelor of Engineering (Hons) (Canterbury)
• Certificate in Civil Engineering (Wintec Waikato)

Chief Strategy & Planning Officer (Acting)

Kat Viskovic

Kat is an experienced leader with a passion for delivering well-planned, sustainable water services that meet community needs. Before joining the water sector in 2025, she was a senior lawyer in private practice, advising infrastructure providers, developers, and local authorities on strategic growth planning, major projects, and regulatory compliance.

Chief Strategy and Planning Officer

Stephen McArthur

Stephen is responsible for the development and implementation of the regional three waters strategy, policy and plans to ensure the sustainable management and growth of water infrastructure. The Strategy and Planning group focus on understanding future demand and the level of investment required to achieve the regional priorities. He also oversees consenting under the Resource Management Act, engineering and modelling advisory services.

Stephen is a senior executive with over 40 years experience within the public sector as a senior executive.  He has worked in local government, central government, NGOs and board governance.  He is currently a Board member for Te Nukuao Wellington Zoo.