Nature-based Solutions for Water Security
There has been a turn toward more long-term economically and environmentally sustainable nature-based solutions (NBS) to achieve water security.
The United Nations has defined water security as the “capacity of a population to safeguard sustainable access to adequate quantities of and acceptable quality water for sustaining livelihoods, human well-being, and socio-economic development, for ensuring protection against water-borne pollution and water-related disasters, and for preserving ecosystems in a climate of peace and political stability”. Multiple climatic and non-climatic trends impact the ability to achieve water security, including the following:
- Climate change is increasing the frequency of flooding and droughts.
- Water-related disasters account for nearly all the most severe disasters over the past several decades.
- Urbanisation is leading to the deterioration of water quality and increased localised flooding risks.
- Agricultural production is diminishing water quality.
- Economic growth is increasing land degradation and biodiversity loss.
- Wastewater is largely untreated globally, impacting human and aquatic health.
The most common means of mitigating the risks from climatic extremes has been increasing investment in conventional — or “grey” — infrastructure, such as dams and levees. However, engineers and decision-makers have come to realise the economic and environmental costs of these solutions. For example, economically, grey infrastructure is often capital-intensive in building, operating, maintaining, and replacing. Furthermore, as it is mainly built to address a specific water management problem, it can amplify risks downstream. Environmentally, grey infrastructure often degrades the quality and quantity of water supply, resulting in ecosystem degradation.
Nature-based solutions for water security
There has been a turn toward more long-term economically and environmentally sustainable NBS that provide equivalent or similar benefits to grey infrastructure. NBS are natural or semi-natural systems that utilise nature’s ecosystem services to manage water resources and associated risks. NBS comes in a variety of shapes and sizes and is implemented in a wide variety of contexts. For example, at the urban level, NBS includes green roofs that mitigate urban flooding while providing multiple co-benefits (including improving air quality, reducing the urban heat island effect, and providing a space for social activities). NBS also includes constructed wetlands for naturally treating wastewater at the landscape level while lowering carbon emissions and providing a habitat for wildlife. Overall, NBS solutions:
- Increase the water infiltration and storage capacity of wetlands and soils to reduce the impacts of floods.
- Help purify polluted water — the equivalent grey infrastructure solution is wastewater treatment plants.
- Mitigate droughts by releasing water from natural storage features such as lakes and aquifers for both human and natural use.
- Appreciate over time with the regeneration of nature and its associated ecosystem services.
Case: Bangkok’s Chulalongkorn Centenary Park Storing Excess Floodwater
Bangkok’s 11-acre Chulalongkorn Centenary Park is designed to mitigate climatic extremes. The Park has been designed as a container, holding up to one million gallons of water during extreme precipitation events. The raised green roof — which is over 5,000 square metres — directs runoff through sloped rain gardens into a constructed wetland where it is naturally filtered before it settles in the retention pond. The Park also provides numerous social co-benefits, include space for meditating and reading. Furthermore, large tanks are sited below the roof to hold up to 250,000 litres of runoff from the green roof. This stored water can provide the Park with enough irrigation water for 20 days during the dry season.
Case: Singapore Integrating NBS with Grey Infrastructure
Singapore’s Public Utilities Board’s Active, Beautiful, Clean (ABC) Waters programme is implementing a range of NBS projects across the city-state to help slow down runoff and prevent localised flooding. The programme also aims to open water bodies for community and recreational use while providing more engaging and experiential ways for the public to learn about water and encouraging the public to become guardians of Singapore’s water resources. PUB has undertaken improvement work on the 3.2 km-long Bukit Timah First Diversion Canal. This work included a $3.9 million ABC Waters project along an 800-metre-long stretch of the canal with NBS features including three rain gardens, designed to improve the quality of the water flowing into the canal, as well as new shelters, benches, fitness equipment, a wetland, and paths for jogging and cycling. Rock walls and creeper plants will also line the canal banks.
Case: Yorkshire Water’s New Constructed Wetland for Wastewater Treatment
Yorkshire Water in the United Kingdom is creating a new integrated constructed wetland at its Clifton wastewater treatment plant. The project will create approximately 4,000 square metres of interconnected ponds planted with over 20,000 wetland plants. The ponds will have a natural slope, using the local impermeable clay geology with wetland plant species to remove phosphorous from treated water before it is returned to the environment. Twenty-five different plant species will comprise the total number of wetland plants used. Each species is carefully selected to promote diverse habitats, with plant species that support bees and other pollinators to increase biodiversity favoured. The constructed wetland will reduce energy usage in the treatment processes, facilitating the water company’s transition towards reaching carbon net-zero by 2030.
The take-out
With water security at risk from multiple climatic and non-climatic challenges, locations worldwide are implementing a variety of NBS to manage both water quality and quantity while generating multiple co-benefits.
Join the conversation on the following LinkedIn groups: Urban Water Security, Our Future Water, Circular Water Economy, Blue-Green Infrastructure, Nature-Based Solutions, and Urban and Regional Futures
