El Niño conditions forecast for summer 2026 are prompting researchers to explore unconventional cooling solutions for urban heat. Dr. Laura Fernandez and her team at Macquarie University are investigating whether recycled water irrigation can reduce temperatures in Western Sydney, a region vulnerable to extreme heat during El Niño events.
The research focuses on using treated wastewater to irrigate trees, which cool their surroundings through evapotranspiration, the process where plants absorb water and release it as vapor. This dual approach addresses two problems simultaneously: water scarcity and urban heat.
Western Sydney already experiences some of Australia's highest temperatures, with the urban heat island effect intensifying conditions in sprawling suburbs. El Niño typically brings warmer, drier conditions to eastern Australia, raising the stakes for water management and temperature control.
Recycled water offers practical advantages. Australia's cities have existing infrastructure for treating and distributing wastewater, and using it for irrigation reduces pressure on freshwater supplies. Trees irrigated with this recycled water can maintain leaf cover and cooling capacity even during drought conditions that would otherwise force water restrictions.
The Macquarie University study measures temperature changes in areas where recycled water irrigation supports tree growth, comparing them to control areas. Results could influence urban planning strategies across Australia's hottest regions.
However, limitations exist. Recycled water quality varies by treatment level, and establishing sufficient tree coverage to meaningfully cool large urban areas requires sustained investment and maintenance. The approach works best as part of broader urban cooling strategies that include green roofs, permeable pavements, and reduced heat-absorbing surfaces.
Fernandez's research arrives at a critical time. Climate projections show El Niño events may become more frequent, and Australian cities must adapt to sustained heat. If recycled water irrigation proves effective at local scales, it could become standard practice in drought-