Researchers Take Deep Dive Into Climate Change Effects on Stormwater and Wastewater

Researchers Take Deep Dive Into Climate Change Effects on Stormwater and Wastewater

Climate change is the great global challenge of our time. But who gives thought to its effects on our stormwater and wastewater infrastructure?

These subterranean systems are notable for the fact that they are invisible, are taken for granted and we give little or no thought to their vulnerability to climate change. Yet our stormwater and wastewater assets are valued at well over $20 billion and include 24,000km of public wastewater networks, some 3000 treatment plants and more than 17,000km of stormwater networks.

Much of that infrastructure however, is poorly designed for the extra pressures that climate change will bring - from sea level rise, to increases in the frequency and intensity of storms. The wastewater and stormwater networks of this country’s most heavily populated coastal areas, including Christchurch, Bay of Plenty and Wellington, are most at risk.

Early in 2017, the Deep South National Science Challenge Impacts and Implications Programme brought together a team of experts to discuss the challenges and concerns for the stormwater and wastewater sector in Aotearoa New Zealand. The team included academics and scientists, industry groups, Government policy analysts, water service providers and consultants.

The discussion resulted in a paper designed to outline our current knowledge of water infrastructure vulnerability and to prioritise research needed to prepare our stormwater and wastewater systems for the changes they face.

One of the people involved was T+T Climate and Resilience expert, James Hughes.

James is a contributor to the paper, Climate Change & Stormwater and Wastewater Systems.

“Stormwater and wastewater systems have the potential to be adversely affected by severe storm events, sea level rise or drought”, says James, who co-authored the report alongside researchers from Victoria University of Wellington, Waikato Regional Council, University of Waikato, Waikato Regional Council, Infometrics, NIWA, Opus, Motu Research, Ngāti Mākino Iwi Authority, and University of Canterbury.

The paper highlighted the devastating effects of the recent Edgecumbe floods as an example of the vulnerability of stormwater and wastewater networks to climate change. April’s torrential rains caused raw sewage to float through the town’s streets, making the clean-up near impossible. Today, 500 homes are still unliveable, their inhabitants still displaced, and flood-proofing the town remains a distant goal.

A lot of the future impacts of climate change are still uncertain. Scientists have yet to fully understand how it will unfold across different regions, specific locations and the timescales involved.

So what do we know for certain?

  • Sea level rise will affect all coastal infrastructure and, as many of our networks use gravity to discharge water, the most costly areas of the network are often located in low-lying areas or on the coast. Increasing sewage overflows, salt water corrosion of pipes and exposure to liquefaction are all likely.
  • An increase in the severity and frequency of coastal storms will also affect coastal infrastructure, in particular, causing increasing flooding, physical damage, and electrical failure at treatment plants.
  • More extreme rainfall events will add stress to the system by overwhelming networks, restricting maintenance opportunities and increasing the occurrence of wastewater infiltrating stormwater. The researchers say the flow-on effects for health, ecology, cultural and recreational spaces, and drinking water supplies are concerning.
  • Drought will also affect networks, disrupting the gravity-fed systems by slowing flow, which will lead to blocked pipes. Particularly lengthy droughts can also affect wastewater treatment processes, creating functional and safety concerns.

The research team have since submitted two proposals based on their work to the Deep South National Science Challenge, James says. You can read the full report here.