Economic modelling functionality of SCA's water supply system model (wathnet) for asset planning

The Sydney Catchment Authority (SCA) uses Wathnet, a generic water balance model for strategic and operational planning of the Greater Sydney water supply system. The model is run for a series of synthetic replicates containing stochastic climate and streamflow data similar to historic data. The SCA's water supply system yield is the maximum annual average demand that can be supplied by the system whilst conforming to the design criteria. Sydney's raw water supply system is designed to meet service standards to ensure supply continuity and to minimise the frequency and duration of water restrictions. The supply system's performance is assessed against a series of criteria such as reliability, robustness and security. The WATHNET model was used to develop Greater Sydney's Metropolitan Water Plan in 2004, 2006 and 2010 and recently for the Warragamba Dam environmental flow assessment. After the Metropolitan Water Plan scenario modelling, all of the scenarios were costed for further assessment. This was done outside the Wathnet system model. The SCA saw benefits in being able to perform the economic assessment of the system's performance for each of the synthetic inflow replicates through the system model and has progressed work in this area The new version of Wathnet modeling software incorporated an economic functionality along with the water supply system simulation capabilities. A new model was built to represent SCA's water supply system and validated against the previous model. The purpose of this paper is to demonstrate the new Wathnet model's economic modelling functionality and its application in asset and system planning