Globally, the effects of climate change are felt with rising temperatures, droughts, heatwaves, and more frequent and severe storm events impacting water quantity and quality. In response, water managers need to ensure that communities are resilient to water scarcity pressures and water excesses and that the natural system and its associated ecosystem services are protected and enhanced.
In addition to investments in resilient physical and technological infrastructure, it will be critical to enhance institutional structures, incentivise sustainable user behaviours, and improve ecosystem management as part of a holistic approach to water management.
For cities, the primary strategies available to enhance the resilience to climatic extremes include applying demand management, developing alternative water sources, and implementing blue-green infrastructure (BGI).
Demand management
With regards to water scarcity, water utilities have traditionally relied on large-scale, supply-side infrastructural projects such as dams and reservoirs to meet the increased demand for water (supply-side management). However, these projects are costly, both economically and environmentally. In contrast, demand management involves the better use of existing water supplies before plans are made to increase supply further. Specifically, demand management promotes water conservation during normal and abnormal conditions, through changes in practices, culture, and people's attitudes towards water resources.
Sydney's New Flexible Water Prices
The Independent Pricing and Regulatory Tribunal New South Wales have set new prices for Sydney's water to enhance resilience to climatic extremes. Since 1 July 2020, Sydney Water customers' price for water is based on dam levels. When dam levels are above 60 percent, customers pay $2.35 per kilolitre of water. When dam levels fall below 60 percent, the price of water increases to $3.18 per kilolitre. While the Tribunal has set a higher water usage charge, it has reduced fixed charges for water and wastewater, resulting in customers being rewarded for always saving water, even outside of drought. Also, a higher price during periods of drought rewards customers who reduce their water consumption when it is most scarce. Simultaneously, the new prices provide Sydney Water with $4.6 billion for capital projects, ensuring the utility can maintain or improve its level of service and environmental performance.
Alternative water sources
Even with successful demand measures, there are regions where water scarcity requires looking for alternative water sources. This creates a need for new sources of freshwater beyond surface and groundwater utilisation. Alternative water sources range in size from onsite non-potable reuse systems in housing developments to city-wide water recycling facilities for industrial use.
Singapore's NEWater
Singapore's Public Utilities Board recycles treated used water into ultra-clean, high-grade reclaimed water: NEWater. In total, five NEWater plants supply up to 40% of the city-state's current water needs. By 2060, it is projected that NEWater will meet up to 55% of Singapore's future water demand. NEWater is created from a three-step process involving microfiltration, where microscopic particles including bacteria are filtered out, reverse osmosis, in which contaminants are removed to create high-grade water, and ultraviolet disinfection, where water passes through ultraviolet light ensuring any remaining organisms are eradicated. Because of its ultra-clean state, NEWater is used for industrial and air-con cooling purposes at wafer fabrication plants, industrial estates, and commercial buildings.
Blue-Green Infrastructure
Many cities are turning to BGI solutions to enhance climate resilience and restore the health of ecosystems, where BGI is a strategically planned network of natural and semi-natural areas that are designed and managed to reduce localised flooding risks, improve water quality, and enhance liveability.
Hamburg's multifunctional sports stadium
Hamburg Wasser is building an underground storage and infiltration system under the Hein Klink Stadium in Billstedt to prevent localised flooding as part of Project RISA. In the event of heavy rain, the excess water will flow in the future through a newly laid channel over a settling shaft into the trenches under the Hein Klink Stadium. In the first step of construction, trenches were built under the sports field to absorb excess water and gradually release it to the ground. In the next construction step, excess water will be led from the street to the sports field via a lockable culvert which has a diameter of 50 centimetres and is 75 metres long. On its way, the water will pass through a settling shaft. There, sand, tyre debris and other solids will be deposited on the floor, and the roughly cleaned rainwater will then flow onto the sports field. Once the system is completed, the new surfaces on the sports field will be applied. In total, the system will absorb more than 500,000 litres of water during a heavy rainfall event.
