Securing a resilient water future for Greater Bunbury

Water planning rarely fails suddenly. More often, it drifts. Demand edges beyond forecasts, dry years arrive more often and groundwater systems recover more slowly than expected. On paper, supply still balances. In practice, resilience erodes quietly until systems approach their limits and choices narrow.

This quiet misalignment was the signal facing Greater Bunbury, a region that continues to grow while experiencing increasing climate variability.

In this environment, water demand is shaped by more than population alone. Extended dry conditions reduce groundwater recharge and increase reliance on scheme water as private bores fail. Warmer conditions influence how day-to-day water is used. These factors can compound quickly, pushing systems closer to their limits earlier than forecast.

For Aqwest Bunbury Water, the primary drinking water provider for around 18,000 properties, this reality became clear in the 2023-24 financial year when annual demand exceeded the long‑held licensed groundwater allocation of 7.6 gigalitres per year well before previous projections suggested it would. The exceedance reflected the combined effect of growth, climate conditions and changing patterns of use rather than a single driver. What first appeared to be a short‑term issue quickly raised a more fundamental question. Was the existing planning framework still fit for the conditions emerging on the ground? Our work updating the Greater Bunbury Urban Water Strategy shows how adaptive planning can respond to real world signals while still giving clear direction for investment and decision making. It also reflects a broader shift across the water sector as utilities respond to growth, climate variability and rising community expectations. 

When Aqwest sought approval for an increased groundwater allocation, the regulator required a Source Development Plan to support the request. This requirement shifted the conversation.

The task moved beyond identifying additional supply. It created space to step back and examine what was driving demand, how those drivers might change, and how future decisions could remain credible under a range of conditions.

This distinction matters. Planning that focuses solely on adding supply risks responding to symptoms rather than underlying causes. An adaptive approach asks different questions. How does demand change when dry periods last longer than expected? What happens when climate and population pressures converge? When do existing sources reach their practical limits, and how much lead time is needed to bring alternatives online? 

A defining feature of the updated strategy is the move away from reliance on a single demand forecast.

Instead, the strategy is built around scenario‑based planning. Through a collaborative process with Aqwest, we identified the factors most likely to influence future demand and water availability. These included population growth, investment capacity, regulatory obligations, workforce capability, community expectations around water use and the impacts of climate variability.

From this, three planning scenarios were developed.

The current scenario reflects a business‑as‑usual pathway based on existing resourcing, investment levels and service areas under a mid‑range climate outlook.

The optimistic scenario considers stronger investment support, increased awareness of the value of water and expanded use of fit‑for‑purpose supply under more favourable climate conditions.

The challenging scenario explores higher demand driven by climate impacts, reduced workforce capacity, increased competition for water resources and constrained groundwater availability.

Together, these scenarios create a shared language for uncertainty. Rather than predicting a single future, they allow decisions to be tested across a range of plausible conditions and highlight where risks begin to emerge.

A critical shift in the strategy was integrating climate variability directly into demand forecasting.

Population growth remains important, but on its own it does not capture how climate conditions influence both system performance and customer behaviour. In Greater Bunbury, extended dry periods were already showing how declining rainfall slows aquifer recovery while increasing reliance on scheme water.

To address this, 15‑year population growth forecasts were combined with climate modelling to develop demand pathways that reflect both demographic change and environmental variability. This approach moves forecasting beyond averages and shows how quickly pressures can escalate under more challenging conditions.

For decision‑makers, this clarity matters. It highlights when existing sources are likely to reach their limits and when investigations, approvals and investment decisions need to begin. With major water source projects often taking close to a decade from initial investigation to delivery, timing is critical.

With future demand pathways defined, we assessed more than 15 potential water sources using a multi‑criteria framework that considered economic, social, regulatory and technical factors. This recognised that viable solutions must work across multiple dimensions.

Groundwater remained the most accessible and cost‑effective option in the short to medium term. However, the analysis showed it could not meet long‑term demand, even with additional allocations. This shifted the focus from extending existing sources to building a diversified supply portfolio over time.

We explored a range of options including seawater desalination, expansion of fit‑for‑purpose water reuse and targeted efficiency measures.

Efficiency plays an important role. Actions that reduce demand or losses can be implemented earlier than new sources, helping to defer future infrastructure while managing affordability and keeping options open as conditions evolve. 

While grounded in technical analysis, the purpose of the strategy is fundamentally about people.

Reliable water supply underpins housing, health services, education, local business activity and community confidence. When systems come under stress, the impacts are often felt first by households least able to absorb higher costs or restrictions.

By identifying future constraints early, the strategy supports proactive investment rather than reactive responses. This allows upgrades to be staged sensibly, engagement with regulators to occur earlier and communication with customers to be clearer and more transparent.

Supporting the community to understand how water systems are changing and why decisions are being made plays a critical role in building trust. In this sense, resilience extends beyond infrastructure. It includes fairness, predictability and shared understanding.

A key outcome of the updated Greater Bunbury Urban Water Strategy is its focus on action.

The strategy sets out a clear 10‑year roadmap with key investigations, decision points and internal milestones such as treatment facility upgrades and source development studies. It also provides a longer‑term outlook to guide planning.

By identifying when climate‑independent sources are likely to be required, the strategy brings visibility of long lead times and supports better alignment between technical planning, regulatory processes and investment planning. This reduces the risk of last‑minute decisions made under pressure and supports more stable long‑term outcomes for the community.

While Greater Bunbury has its own local context, several lessons apply more broadly.

Climate variability needs to be treated as a core demand driver. Scenario‑based planning supports better decision‑making by testing strategies against uncertainty rather than relying on a single path. Diversified supply portfolios reduce exposure to single‑source risk. Efficiency remains a strategic tool that supports affordability and resilience. Early collaboration between utilities, regulators, planners and technical specialists supports smoother pathways when approvals, funding and delivery decisions are required.

These principles are increasingly relevant as water utilities across Australia respond to rising demand, changing climate conditions and growing expectations around reliability, affordability and transparency.

Across the water sector, planning approaches are evolving. Adaptive, scenario‑based strategies balance structure with flexibility, providing clear direction while allowing decisions to respond to real‑world signals rather than fixed assumptions.

For Greater Bunbury, this approach has clarified the pathway toward long‑term water security. More broadly it demonstrates how thoughtful planning can support resilient communities by anticipating change, engaging openly with uncertainty and placing community benefit at the centre of decision‑making.

Resilience is built early. It is built through better forecasting, clearer choices and planning approaches that recognise water as both a critical service and a shared community resource.