Surface water supplies are taken from rivers, lakes or ponds. Surface water can provide a consistent and manageable source of water. However, it is subject to greater risk of contamination than groundwater and therefore usually requires treatment. Contamination is most likely to be with microbiological pathogens from human and animal excreta. There is also the possibility of accidental or deliberate pollution by industries or the agricultural community.
What are the likely sources of contamination in the river in the figure above?
Excreta from the cattle will be washed into the river water. Their hooves have disturbed the ground so soil is also likely to be washed in. The road passing over the bridge in the background could be a source of pollution from cars and lorries.