One of the most important reasons for using reliable water sources is to reduce

Is to reduce faecal-oral diseases of which diarrhea, estimated to kill over three million people a year. 

An adequate quantity of water, is more important in controlling non-epidemic disease and allows better hygiene and thus can prevent disease. Sanitation alone has its greatest impact on infections. And better results come from observing practical outcomes such as the use and maintenance status of facilities, or improvements in hygiene practice. 

Maybe haha