Water has zero calories. Additionally, water contains no fats, proteins, cholesterol, vitamins or carbohydrates. Typically, water contains traces of sodium, potassium and calcium, although the mineral content of water varies considerably by source.
Depending on the rock layers around groundwater wells, minerals such as iron or calcium carbonate can leech into water supplies, though this leeching has no effect on the calorie count. Other forms of runoff, such as fertilizer or mining slurry, can contaminate water supplies in a region and make the drinking water unsafe for human consumption. As the human body is comprised of 55 to 78 percent water, significant frequent water intake is required for survival.