Water treatment plant. Picture: SUPPLIED
A water treatment plant. Picture: SUPPLIED

CAPE Town plans to launch a fund by the end of 2017 to improve its water supply by restoring native shrub in its watersheds and aquifers.

With rain patterns uncertain due to global warning, protecting indigenous vegetation should yield more water for consumption, said Colin Apse, director for freshwater conservation in Africa at The Nature Conservancy, a US-based non-profit group working with Cape Town.

"Depending on the green infrastructure investments chosen, a Cape Town water fund could lead to a range of climate change adaptation benefits," Apse said.

In recent years, scientists have researched the impact of alien plant invasions in SA’s watersheds and river-bank areas.

In 2014, experts with the Council for Scientific and Industrial Research found that restoration of Cape Town’s native shrubland, called fynbos, and removal of invasive thirsty plants cut water consumption by vegetation and increased rainwater recharge.

In 1995, SA started a working-for-water programme that helped control invasive plants and alleviate poverty with jobs for clearing unwanted vegetation.

Yet, despite government investing more than R3bn in clearing 2-million hectares in the first 15 years, SA’s watersheds are still heavily invaded by alien plant species, said Louise Stafford, Cape Town’s green jobs programme manager.

About 19-million hectares were estimated to be affected across the country.

Money raised through the fund would be used to step up existing efforts, she said.

Councillor Johan van der Merwe said the fund would pay for conservation in Cape Town’s west coast area.

The fund’s value has yet to be fixed. Money sources will include public allocations, foundations, international donors such as the Global Environment Facility, and water and power utilities, said Van der Merwe.

A city in need

Cape Town’s metropolitan area is 2,445 square kilometres, and its population of about 3.8-million people is rising at almost 3% a year.

Ensuring an adequate supply of water during recurring droughts is critical if the city is to develop sustainably and safeguard economic growth, experts say.

Van der Merwe said Cape Town’s 14 reservoirs and two aquifers – the largest being Atlantis Aquifer – had to be managed better. The Atlantis Aquifer protection zone would probably be the fund’s first focus.

Stafford said recharge of the Atlantis Aquifer was reduced by dense alien plant infestation.

"Invasive plants use more water than indigenous plants, due to their deep root systems which can travel further and absorb more water, (and) their larger leaf surface area also increases evapotranspiration," she said.

The fund’s investments, while improving water security and ecosystem functions, may also boost the impoverished surrounding towns of Atlantis, Mamre and Pella, through jobs in controlling invasive plants and restoring fynbos, Van der Merwe said.

More could come indirectly from tourism as people will be attracted to view flowers further up the west coast, he added.

A study on urban water in sub-Saharan Africa, released by the Nature Conservancy in July, said 28 cities could improve water supplies for more than 80-million residents by investing in conservation, including forest protection and good farming practices on land that drains into rivers, lakes and aquifers.

In Cape Town, better water quality could offset the costs of conservation due to lower spending on water treatment and desalination, providing "dramatic return on investment", the report said.

University of Cape Town biologist Mike Lucas said SA is a water-stressed country with average rainfall of less than 400mm a year. That has to service high demand from domestic use, agriculture and industry.

In the Western Cape, climate models predict the average amount of rainfall will decrease, with less occurring in winter and slightly more in the summer – but with an overall net loss.

"Our precious water reserves will need to be conserved and recycled, particularly in the face of a growing population that rightly demands proper services, including potable water," Lucas said.

Changing rainfall will also affect plants and biodiversity, with fynbos – which prefers hot, dry summers – pressured by the invasion of alien grasses competing for a declining amount of water.

Clearing invasive vegetation could help cut water use, particularly where replaced by indigenous plants – but not if crop cultivation is seen as a viable alternative on that land.

"This may result in more water being used than is saved," Lucas warned.

Reuters and Thomson Reuters Foundation