The world’s freshwater supplies are at risk. This is a threat to all life on the planet. It’s therefore no surprise that water purification has turned into a multibillion dollar global business.
The World Bank estimates that at least $150 billion a year will be required to give the entire global population access to clean drinking water by 2030. There’s no silver bullet when it comes to the technology available to tackle severe water shortages. Several options therefore need to be explored.
One purification option can be found in nature – wetlands. Research shows that wetlands are able to act as filters of water in numerous ways. This includes the uptake of pollutants by plants, soils and even microbes present in the wetlands.
They’re are also able to mitigate the effects of floods and store carbon dioxide, while aiding in providing livelihoods and holding cultural importance.
We conducted an analysis of the Rietvlei freshwater wetland on the outskirts of the coastal city of Cape Town, in South Africa’s Western Cape province, to understand the soil, surface and groundwater, because of the intricate interplay between water bodies in the area as well as the reliance of the entire ecosystem on water flow between them.
We found that the wetland had been impacted due to water being drained from it as well as from contamination. This, in turn, is affecting the well-being of people, animals and plants that depend on the wetland. Our research underscores the fact that wetlands are important for the functioning of ecosystems and need better care.
This will help protect the environment and the earth’s already strained water resources.
What we found
A number of factors have affected the Rietvlei body in the past.
One is that it’s near residential areas, a wastewater treatment plant and a petroleum refinery. This has implications for water in the wetland, due to the discharge from industry and households as well as consumption upstream.
In addition, the natural water flow in Rietvlei’s immediate vicinity has been altered. This is due to the canalisation, which is the lining of the river bed and banks with concrete to form a channel, of the Diep River as well as the use of water by farmers in the area. The amount of water in the river has been drastically reduced and its quality has been affected, which has an impact on plants and animals as well as human health.
Then there’s the issue of contamination: we found that flooding water from the river and on the surface in the rainy season filled the cracks in the soil formed during the dry season. The flood waters flushed salts into the groundwater through cracks. Water quality and plant survival are threatened by the salinity.
Other factors have also increased the amount of salt in the groundwater. One of them is over-pumping during a recent drought. Cape Town drew large volumes of groundwater daily and sea water may have moved into the wells to replace it.
Another possibility is that the local geological formation contains a salt deposit which is being dissolved in the groundwater.
These findings shed light on the water quality in the wetland and show what’s needed to better understand the functioning of wetlands in order to improve their management.
Protecting a precious resource
A report which examined the state and trends of wetlands around the world, the Global Wetland Outlook, recently examined the status of wetlands in line with the Ramsar Convention – the only international treaty focused on wetlands. It found that wetland quality and quantity are declining and this has immediate and long-term effects on biodiversity and human livelihoods. These include declining food and water security.
As a result, many countries are now employing policy and legislation to strengthen the application of the Ramsar Convention and the United Nations’ Sustainable Development Goals.
Wetlands are sensitive systems which are affected by human activity. They need to be protected because they play a critical role in the ecosystem. Streets and rivers must be kept clean to stop pollutants from migrating into rivers and ultimately into wetlands. Industry should be more responsible when emitting discharge into rivers. This means stricter rules regarding the quality of water that is pumped from industrial processes into the environment.