That's why the South African government has invested in installing more than 23,000 rainwater tanks to collect and store rain for use in the households of rural villages.
But a new study suggests pathogens regularly inhabit these harvested rainwater tanks, and that they could be a public health hazard.
The study was led by Wesaal Khan and his fellow researchers at the University of Stellenbosch. To get an idea of the risk of using recycled rainwater, Khan and a team of scientists regularly collected water samples from tanks at the Kleinmond Housing Scheme -- a sustainable housing project built and managed by the South African Council for Scientific and Industrial Research and the Department of Science and Technology.
The samples turned up a range of different bacteria, several of them danagerous. The illness-causing Legionella was found in 73 percent of samples, and nearly half of all samples contained Klebsiella, a rod-shaped bacterium that can cause pneumonia, urinary tract infections, soft tissue infections and other health problems. A quarter of the water samples contained Giardia, a harmful parasite.
Although most of the problematic contaminants are found naturally occurring in fresh water, a small percentage of the samples contained Salmonella and Yersinia, an indication of fecal matter from humans and animals.
The collected rainwater is meant to be used only for washing clothes and housecleaning. But in polling villagers that use the water tanks, researchers found about a quarter of people also drink the water. Many of these villagers are without formal education and remain unaware of the risks of drinking the harvested rainwater.
The researchers, who published the study in Applied and Environmental Microbiology, say the risk of drinking contaminated rainwater remains the biggest obstacle to expanding sustainable solutions, like rainwater harvesting, in drought-prone countries like South Africa.