Remains a complex problem, but time is running out Some 150 years after John Snow discovered that a contaminated water pump was responsible for a localised cholera outbreak, two million people world wide still die every year from water related diarrhoeal illnesses.1 2 In 1854 John Snow did not know that an organism was responsible, but meticulous epidemiological studies and common sense led him to close the Broad Street pump, saving hundreds of lives. At the beginning of the 21st century, despite our extensive knowledge of the causes and prevention of water associated illnesses, 1.1 billion people around the world have no access to clean water and 2.4 billion have inadequate sanitation.1 Ideally, everyone would have the same high quality, abundant quantity water supply that people in the developed world take for granted: we flush drinking water down our toilets and wash ourselves, our clothes, and our cars in it. But usually it is a trade off between quality and quantity. ![][1] Credit: TRYGVE BOLSTAD/PANOS The quantity of surface water (rivers, lakes, ponds, etc) is variable, depending on rainfall, and is poor quality, whereas groundwater (found in permeable rocks more than 100 metres underground) is usually high … [1]: /embed/graphic-1.gif