Integrated water source management modelling: A risk based approach

Watercare is responsible for supplying high quality drinking water to more than 1.2 million people. Over the past ten years Watercare has used an Integrated Source Management Model (ISMM) to assist operational and management decisions. This model, developed by Tonkin & Taylor Ltd, is crucial to the management of Auckland’s water sources, and doing so from an integrated risk management, cost minimisation approach.

At the heart of the ISMM is an innovative but now proven optimisation strategy that balances risk-weighted damages from potential supply shortfalls against marginal operational cost. In essence the conflicting objectives of cost-of-operation minimisation and system yield maximisation are resolved based on cost objective functions determined from structured hydrological risk analysis.

The model has become established as an essential tool for Watercare managers, to assist the sustainable management of Auckland’s water supply.

During the summer of 2008, when other cities around New Zealand were under water use restrictions, there were no such restrictions in Auckland. Watercare achieved this by effective management of its aquifer, dam and river sources, with the ISMM as a critical tool to inform the Watercare Board on the risk of water shortage and assist management operational decisions.