photo of Lake Macquarie, NSW, Australia at sunset, shades of orange and blue on the water, wooded shoreline in background

Using modelling technology to undertake Risk Analysis for Hunter Water’s Distribution Network

Background

Hunter Water Corporation (HWC) is the second largest water and sewerage utility corporation in New South Wales. It serves a population of almost 600,000 people spread across 6,671 square kilometres in the areas of Cessnock, Lake Macquarie, Maitland, Newcastle, Port Stephens, Dungog and small parts of Singleton.

HWC’s water distribution network delivers an average of 188 megalitres of water per day and is split into six reticulation models that contain the region’s 123 water zones. HWC undertakes an annual risk review to assess the compliance of the network against system performance standards and planning regulatory requirements.

map of Hunter Water service area

  • Hunter Water Corporation (HWC) undertakes an annual risk assessment to determine its exposure to risk over a 12-month period.
  • These risks are categorised by factors including water continuity and water pressure standards.
  • HWC has determined the parameters that make a risk low, medium and high.
  • These parameters are applied to the different zones that make up the reticulation models.
  • InfoWorks WS Pro is used to run the models and measure the level of risk.
  • The output is used to inform OPEX and CAPEX planning and is fed back to the board and the regulator.

The Challenge

The annual network risk review is a crucial decision support tool for HWC. The tool helps determine the planning for both capital and operational expenditure priorities. It also determines the regulatory compliance based on the risk ratings of individual assets. The risk review is based on the corporation’s Enterprise Risk Management (ERM) framework, and the framework determines the level of risk by plotting the consequence of an asset failing with the likelihood of failure.

The ERM framework utilises a risk matrix that involves many parameters based on system performance and capacity. For example, the consequence criteria include water pressure and service continuity standards, while the likelihood criteria include reservoir capacity and performance. A hydraulic model using InfoWorks WS Pro enables HWC to calculate these many parameters at different demand scenarios for all zones and assets in the entire network.

quote

Understanding risks of our current assets is critical for the continuity of service to our community.

Andrew Tjiptadi Service Planning Engineer, Hunter Water Corporation

The Project

The risk review process is a top-down approach which takes input from HWC’s water network zones hierarchy, individual water network zones information and the growth areas. Simulation results from the hydraulic model are generated to assess system performance and to analyse reservoir capacity.

The risk analysis then involves analysing the consequence and likelihood criteria which helps determine the risk scales on each individual water zones. RAG (Red Amber Green) status is flagged for each individual zone based on supply continuity and asset criticality, which returns results for evaluating uncontrolled risks, controlled risks and corresponding proposed actions.

This is then used to deliver a Risk Mitigation Strategy which has a focus on OPEX – operational contingency strategy development and review, and CAPEX – service strategy review and development. Out of this comes the Operating License and Servicing Standard review, a regulatory report required by the regulator and developers.

The Hydraulic Model

The hydraulic model is an explicit all-mains digital representation of the entire water distribution network. It simulates the performance of key water assets like reservoirs, pump stations, valves, meters, hydrants, etc. It also represents multiple scenarios including the current and future zone demands as well as the current and future number of properties. Model runs are used to show how many customers experience low pressures during Peak Day Demand (PDD) and how many experience high pressures during Average Day Demand (ADD).

The model is also used to perform asset criticality. Critical Link Analysis (CLA) is a run type in InfoWorks WS Pro which allows the automated testing and reporting of the effects of failure of a selection of links based on the time of outage and method of failure. CLA runs are performed for every shut off block or pipe sections to evaluate network resilience, pump stations criticality and hydrant locations for firefighting requirements.

The hydraulic model also gives the team a clear understanding of how the reservoirs will perform during Average Day Demand, Peak Day Demand and Extreme Week Demand.

The Result

Sample result - asset criticality

bar graph showing pump station criticality

The value of the hydraulic model is demonstrated by the analysis it is used to perform. InfoWorks WS Pro gives Hunter Water the information it needs to understand the system’s performance as well as capacity. Under normal circumstances InfoWorks WS Pro is used to understand the operation of the network now, and how it will operate in the future. Hunter Water Corporation has taken its modelling capability a step forward to measure and assess risk, and the impact on its customers.

Sample result - firefighting

bar graph of hydrant count vs flow capacity of fire hydrants

The hydraulic model using InfoWorks WS Pro is a hugely useful tool to identify and quantify the consequence of asset failure to our customers. This knowledge will give us time to plan ahead and allocate the correct resources that would mitigate the identified risks. - Hunter Water Corporation

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