Greener is cleaner - when it comes to improving the quality of drinking water at its source

Over the past decade, Massey University scientists have tested raw water samples from various areas.

They found unsafe levels of E.coli and campylobacter in areas with cows and sheep, while areas with dense native forest had no presence of pathogenic microbes.

Study co-author Professor David Hayman says we can improve water quality before it reaches the processing plant.

He says planting more native forest will reduce the amount of animal faeces going into the water.