Yesterday, did your water system troubles seem so far away?

The Beatles nod aside, climate change is often described as a water quantity problem in terms of droughts, floods, shrinking supplies. But for built water systems, it increasingly behaves like a water quality volatility problem. Warmer source waters change ecological and chemical dynamics. Warmer distribution systems accelerate disinfectant decay and microbial behaviour. Extreme rainfall and catchment shocks also play a role, delivering pulses of turbidity and organic matter that can push treatment beyond historical design envelopes. Evidence synthesising warming distribution systems shows concurrent microbial and chemical impacts such as chlorine/chloramine decay, altered microbial communities and mobilisation of components from asset materials. All these facts underscore the importance of system. Siloed thinking when it comes to designing robust built water systems will not suffice.

Research has also shown that atmospheric warming means surface waters (and many groundwater systems) warm too. This alters mixing, oxygen regimes and algal ecology, all of which flow through to water quality impacts such as treatability and downstream stability. The practical message is simple: if you plan and operate as though the past is a reliable guide to the future, climate change will eventually prove you wrong.

 

Stability is no longer a sensible operating assumption

Most water infrastructure was planned around stable historical envelopes. This involves “typical” temperatures, “typical” source quality, and “rare events” staying, well, safely rare.

Climate change impacts vary the baseline and increase volatility: more heat, more extremes, and more compound scenarios that can destabilise water quality. This coupled with boards failing to proactively seek the non‑financial information they need to make evidence‑based decisions, particularly on issues like water, can result in water and climate risks potentially undermining not only organisational stability but the resilience of communities and entire economies.[i], [ii]

From a risk management perspective, the key issue is not that we can’t predict anything. Rather, it’s that we can’t rely on historical distributions to play nice and stay put. That means that risk controls which are designed for yesterday’s envelope can drift out of adequacy without anyone “doing anything wrong” – it’s just that the operating context has moved. And not only that, many jurisdictions have long been formally requiring organisations to take climate change into account in their planning and operations[iii].

 

The Boiling Frog

Just as it is a creeper for the poor old frog, temperature can be thought of as a “master variable” for water quality because it influences many aspects of uncertainty. These include microbial growth, reaction kinetics, disinfectant decay, corrosion dynamics, and by‑product formation. Evidence from a review of warming drinking water distribution systems identifies consistent themes such as: warming can speed chlorine and chloramine decay, alter microbial communities, and increase the likelihood of metals accumulation/release depending on pipe materials, while at the same time, affecting disinfection byproduct dynamics.[iv]

At the source end, the warming story is not limited to a few extra degrees on a graph. Switzerland’s EAWAG highlights that atmospheric warming changes lakes and rivers in ways that matter for consideration in the production of manufactured water[v]. These include altered circulation and mixing, oxygen deficits at depth, and ecological shifts including the spread of some toxic algae.[vi] These changes can affect organic matter character, taste/odour risks, and treatability. Put plainly, warming raises the baseline workload for your designed controls. This makes it easier for system compliance to slip out of control, particularly where residence times are long, which they often are in water distribution systems (including both in the network and in-premise plumbing systems).[vii]

 

Pesky pulses

While pulses tend to be beneficial for your digestive system, pulses or shocks from climate change impacts are a whole other story. Climate change impacts can show up not only as trends but as fluctuations. These include intense rainfall, flooding, and rapid runoff which deliver short‑duration high‑impact water quality events. These events can produce spikes in turbidity, pathogens, nutrients and dissolved organic matter, often on time scales that we find can challenge monitoring frequency, operator response and ongoing compliance.[viii], [ix]

From a treatment standpoint, pulses are particularly painful because process stability matters. Sudden shifts in turbidity and natural organic matter and dissolved organic carbon increase coagulant and oxidant demand, can elevate disinfection byproduct precursor loads and can reduce the margin for error across filtration and disinfection. Climate‑driven fluctuation, not just gradual change, is repeatedly highlighted as a key mechanism linking climate change to water product safety.[x] And while these source and network operator issues might seem less relevant if you are a building designer or facility manager, imagine having to deal with accepting the water quality liability once that water has entered your own system, or even, knowing if it had? Ensuring you have appropriate governance frameworks in place and treatment flexibility to deal with such scenarios, is essential.[xi]

Slippery scenarios

Compound sequences deserve special attention because they create water quality “surprises” that aren’t actually that surprising once you map the chain.

For example:

  • Drought can concentrate dissolved constituents and change catchment responses to runoff.
  • Bushfires can alter catchment cover and generate ash and altered organic matter, with subsequent rains mobilising large loads into reservoirs and rivers.
  • Bushfires that significantly impact on urbanised areas can create conditions where the ash is more likely to increase the toxicity of disinfection byproducts[xii].
  • Urban planning that fails to account for rising temperatures can intensify urban heat island effects. This can then warm water supply pipes[xiii] and push water to temperatures that encourage risky microbial proliferation (think Legionella, Naegleria fowleri, Mycobacterium avium and Pseudomonas aeruginosa, as well as nuisance organisms that can cause taste and odour impacts).

 

Water Uncertainty Flows Through Everything

As discussed in my last Sourceable articleviii, if water quality uncertainty thinking isn’t baked into planning and design, the bill eventually becomes due with interest, to operations and customers. And nobody likes a bill, especially one you weren’t expecting.

To this end, I’ve put together some principles for consideration in climate-ready, water-quality-led planning and operations (Table 1).

 

 

Conclusion: Climate Adaptation Must Include Water Quality, and Whole of System Thinking

Climate change is reshaping built water systems through water quality dynamics: warming source waters, warming distribution networks, more volatile event‑driven loading, and more compound hazards and scenarios. The correct response is not a single technology or a single project, it is a whole‑of‑system approach that links planning, design, monitoring, operations and governance into a coherent risk framework.

If we do this well, we can produce safe, reliable and fit‑for‑purpose water, and reduce the number of times we have to say: “Well… that was unexpected.” Because in 2026 and beyond, “unexpected” is rarely true. It’s usually just not understood or not planned for. And unlike The Beatles, if we want reliable water in a warming world, we can no longer just let it be.

 

Key Takeaways

  • Climate change is as much a water quality as a water quantity problem: warming waters, volatile raw water quality, distribution system warming and compound events converge on the barriers that protect public health and water product integrity.
  • Planning‑to‑operations thinking is no longer optional: historical design envelopes are unreliable; systems must be designed for variability, monitored for drift, and operated adaptively. If uncertainty management isn’t baked in at design, it will bake itself in later (usually at a higher cost).
  • Governance and monitoring must evolve faster than climate change: compliance alone won’t guarantee fitness for purpose, and “bluewashing” is a genuine leadership risk. Whole‑of‑system, risk‑based controls with strong assurance and learning loops should now simply be just core business.

 

Acknowledgements

I’d like to acknowledge the help of Professor Copilot in helping corral my myriad thoughts, in first contemplating this paper, and in helping to correct my mangled grammar. Any puns, pop culture references, alliterations or strange humour, are all my own work. I’d also like to thank my wonderful colleagues, Sarah Loder from The Risk Edge Group and Alex Sommer from Aquacell, for careful review and suggestions.

 

References

[i] See Davison, A. and Loder, S. (2025). Are you being “bluewashed”? What you should know about water risk to protect your bottom line. The Risk Edge Group White Paper. https://www.riskedge.com.au/are-you-being-bluewashed-uncovering-the-hidden-water-risks-to-protect-your-business/

[ii] Australian Securities and Investments Commission (2019) Corporate Governance Taskforce ‑ Director and officer oversight of non-financial risk report. https://asic.gov.au/regulatory-resources/find-a-document/reports/corporate-governance-taskforce-director-and-officer-oversight-of-non-financial-risk-report/foreword/

[iii] As an example, the UK’s Ofwat has just released its final climate change principles. https://www.ofwat.gov.uk/wp-content/uploads/2026/02/Ofwats-Final-Climate-Change-Principles.pdf

[iv] Limaheluw, J.,  van der Aa, M. (2025) Warming drinking water distribution systems in the context of climate change: a scoping review on health-related microbial and chemical water quality effects. J Water Health 1 August 2025; 23 (8): 952–967. doi: https://doi.org/10.2166/wh.2025.059

[v] Contemporary thinking for water security and resilience must include a diverse suite of water products, depending on the end use, end point and end user. This suite includes products such as recycled water (e.g. from sewage effluent, stormwater, food processing), drinking water, stormwater, recreational water (natural waterways as well as swimming pools) and industrial process water.

[vi] https://www.eawag.ch/en/info/portal/news/news-detail/how-much-swiss-watercourses-will-warm-up/

[vii] Davison, A. (2025) Water Risk Management (Now With Added Climate!). Invited presentation to Environment Institute of Australia and New Zealand. August 2025.

[viii] https://www.theguardian.com/australia-news/2019/dec/15/sydneys-drinking-water-could-be-polluted-by-bushfire-ash-in-warragamba-dam-catchment-expert-says

[ix] Cox, P., Fisher, I., Kastl, G., Jegatheesan, V., Warnecke, M., Angles, M., Bustamante, H., Chiffings, T., and Hawkins, P.R. (2003) Sydney 1998: lessons from a drinking water crisis. Journal American Water Works Association, 95 (5). pp. 147-161.

[x] Scaling Up H2O! Podcast 453 Water Risk, Governance, and Community Engagement with Dr. Annette Davison. https://scalinguph2o.com/2025/12/05/453-water-risk-governance-community-engagement/

[xi] Davison, A. (2025) Water Risk Starts at Design: Why Planning to Operations Thinking is Critical for Safe Systems. Sourceable 2025-12-15 https://sourceable.net/water-risk-starts-at-design-why-planning-to-operations-thinking-is-critical-for-safe-systems/

[xii] Justen, P.T., Jaynes, E.K., Beavers, C.A., Alshehri, T., Alam, M., Baalousha, M., and Richardson, S.D. (2025). Impact of Wildland-Urban Interface Wildfires on Drinking Water: Urban Structural Ash Is a Source of Precursors for Toxic Disinfection Byproducts. Environ Sci Technol. 59(27):14030-14040. doi: 10.1021/acs.est.5c04317. Epub 2025 Jul 3. PMID: 40608835.

[xiii] Agudelo-Vera, C. M., Blokker, M., de Kater, H., and Lafort, R. (2017) Identifying (subsurface) anthropogenic heat sources that influence temperature in the drinking water distribution system, Drink. Water Eng. Sci., 10, 83–91, https://doi.org/10.5194/dwes-10-83-2017.

[xiv] Calero Preciado, C., Boxall, J., Soria-Carrasco, V., Martínez, S. and Douterelo, I. (2021) Implications of Climate Change: How Does Increased Water Temperature Influence Biofilm and Water Quality of Chlorinated Drinking Water Distribution Systems?. Front. Microbiol. 12:658927. doi: 10.3389/fmicb.2021.658927

[xv] https://www.eawag.ch/fileadmin/Domain1/News/2024/08/13/umw_whitepaper_binz_etal_2024.pdf

[xvi] There are several experienced providers in this space such as Aquacell (https://aquacell.com.au) which operates globally.

[xvii] Davison, A. (2018) Water governance: a repeating failure. CERM® Risk Insights. #195 10 February 2018 https://insights.cermacademy.com/195-water-governance-repeating-failure-annette-davison/

[xviii] Davison, A., Loder, S. and McLennan, P. (2025) Backflow risk management: a five-part framework for safer water systems. The Risk Edge Group Blog Article. https://www.riskedge.com.au/backflow-risk-management-a-five-part-framework-for-safer-water-systems/

[xix] Davison, A., Loder, S. and McLennan, P. (2025) Is your backflow management system working? A practical monitoring framework for water safety assurance. The Risk Edge Group Blog Article. https://www.riskedge.com.au/is-your-backflow-management-system-working-a-practical-monitoring-framework-for-water-safety-assurance/

[xx] The Risk Edge Group has been collating water-relevant incidents for a number of years as a learning resource for the industry: https://www.riskedge.com.au/incidents-online-tool/

[xxi] Davison, A. and Dyson, M. (2025) Fit for Purpose? Aligning Water Quality with End Use and End User Needs, in a Changing Risk Landscape. The Risk Edge Group White Paper. https://www.riskedge.com.au/is-your-water-really-fit-for-purpose-the-hidden-risks-you-need-to-know/

[xxii] Davison, A. and Loder, S. (2025) Are you being “bluewashed”? What you should know about water risk to protect your bottom line. The Risk Edge Group White Paper. https://www.riskedge.com.au/are-you-being-bluewashed-uncovering-the-hidden-water-risks-to-protect-your-business/.