Dams supplying Cape Town are now three-quarters full after the first season of adequate rainfall following three years of record lows
Reservoirs supplying Cape Town A severe drought in 2017 and 2018 depleted Cape Town's water supplies © TNC

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Clearing non-native trees could unlock two months of extra water per year for Cape Town

TNC report suggests nature-based solutions are a tenth of the cost of ‘engineered’ infrastructure options

Greater Cape Town could cost-effectively tap two months of new water supplies a year just by clearing non-native trees from water catchments, according to new research from The Nature Conservancy published today.

‘Engineered’ options to tackle the effects of drought like desalination plants or reusing wastewater were on average ten times more expensive than removing pine, acacia and eucalyptus trees, commonly called ‘invasive alien plants’, or ‘invasives’, the study calculated.

Its findings formed part of the Business Case for a new public-private mechanism to finance water security, the Greater Cape Town Water Fund, launched in Cape Town today.

Pioneered by The Nature Conservancy, a global conservation organisation, Water Funds identify large-scale water users who need secure and clean supplies ‘downstream’ who pay for nature-based programmes to improve water quality and quantity ‘upstream’.

The concept links public and private sectors around the common goal of using ecological, ‘green’ interventions instead of massive new construction or renovations to existing ‘grey’ infrastructure, such as dams.

Coca-Cola, PepsiCo, Caterpillar Foundation, and Levi Strauss & Co. are among South Africa’s first major corporates to support the Greater Cape Town Water Fund, drawn by evidence that investing in ecological infrastructure is a fast, affordable route to greater water security for businesses and homes.

In total, corporate partners, foundations and philanthropists have already committed close to R53 million (US$4 million) to the new Water Fund. It also has the backing of South Africa’s provincial and national authorities.

Alderman Ian Neilson, Executive Deputy Mayor of the City of Cape Town, said:

“In order to secure our long term water supplies, we need to pursue a range of cost effective strategies. One of those is to clear vegetation in our catchments that reduce the runoff into our dams, such as that proposed by The Nature Conservancy in this report.”

The study’s release comes as dams supplying Cape Town are three-quarters full after the first season of adequate rainfall following three years of record lows. The city faced blanket water rationing in 2017 as households were limited to 50 litres per person per day, and agriculture and industry imposed severe restrictions.

The Nature Conservancy’s research, conducted by Anchor Environmental Services, modelled various investments to increase water supplies to the city and its surroundings.

The leading engineered options to tackle Greater Cape Town’s water shortages - desalination, recycling waste-water, and tapping groundwater supplies - cost on average 10 times more to supply each litre of water than clearing invasive trees. Desalination, the most expensive alternative, was more than 12 times pricier.

By contrast, The Nature Conservancy study found that R372 million (US$25.5 million) could fund a 30-year programme to clear invasive trees and prevent them from returning in the seven priority sub-catchments that supply three-quarters of Cape Town’s water.

As well as being cheaper, this ‘green’ option would deliver more new water than each of the other ‘grey’ options. In its first six years, a programme of clearing invasive plants could yield 56 billion litres of new supplies. That is close to the 58 billion litre capacity of the Wemmershoek dam, one of the four largest supplying Cape Town.

Within 30 years, more than 100 billion litres of additional annual water gains would be achieved compared to the ‘business as usual’ with no intervention. That’s equivalent to one-third of Cape Town’s current annual supply of 324 billion litres.

Andrea Erickson, Global Managing Director of Water Funds at The Nature Conservancy, said:

“The scale of the challenges we face and the speed at which they are growing requires both innovation and evolution. Investing in nature-based solutions to water scarcity can be cost-effective and efficient, and often produces additional benefits compared to conventional built, ‘grey’ infrastructure. The businesses and public funders that are supporting the Greater Cape Town Water Fund share our vision of a water secure future, enabled by natural infrastructure, where people, businesses and nature all have reliable, equitable access to clean water.”

The Business Case study was designed to identify the most cost-effective solution and attract others to join the Greater Cape Town Water Fund, and add to the R53 million (US$4 million) already pledged. Funding is expected to be a complementary mix of public, private and philanthropic finance.

The Fund’s Steering Committee will now work with stakeholders to turn the findings of the Business Case into a strategy for ecological restoration of the Western Cape water supply system. The work will focus on clearing invasive plants from seven priority sub-catchments that together provide 73% of the system’s water. It is anticipated that at least 350 new jobs will be created in the first six years, mostly to make up teams to clear the invasive plants.

Andre Geldenhuys, Divisional Executive at Nedbank Corporate and Investment Bank in the Western Cape, which sits on the Steering Committee, said:

“Everyone in the Western Cape, be they a city resident, the municipal authorities, or a leading business, has a part to play in making sure we can deal with the climatic changes coming our way. The nature-based solutions at the core of the Greater Cape Town Water Fund are the most cost effective way to secure and grow our water resources, and the long-term sustainability of the solutions, coupled with the creation of many jobs in the Western Cape region, make all of us at Nedbank very proud to be a partner to this exciting venture.”

Non-native trees such as pines that ‘escaped’ commercial plantations and seeded hillsides above dams are far thirstier than indigenous vegetation, especially the Western Cape’s fynbos.

They draw more groundwater through their roots, they send more moisture back into the air through evapotranspiration, and they interrupt rainfall that would otherwise run-off into soil and rivers and feed dams.

Restoring habitats is also significantly less environmentally costly than constructing the plants, pipes, pumping stations and treatment pools that desalination, groundwater recharge, and reusing wastewater requires.

Preliminary analysis has shown that an estimated 1.8 billion litres of water is lost annually due to alien plant invasions on the Atlantis Aquifer north of Cape Town.

A year-long research project is already underway there with a pilot team clearing invasive plants to determine their impacts on groundwater. An estimated 70% of the Aquifer’s surface area has some level of invasion, with 9% of the area densely invaded.

The Nature Conservancy is a global conservation organization dedicated to conserving the lands and waters on which all life depends. Guided by science, we create innovative, on-the-ground solutions to our world's toughest challenges so that nature and people can thrive together. We are tackling climate change, conserving lands, waters and oceans at an unprecedented scale, providing food and water sustainably and helping make cities more sustainable. Working in 72 countries, we use a collaborative approach that engages local communities, governments, the private sector, and other partners. To learn more, visit www.nature.org or follow @nature_press on Twitter.