In sum, the article says:
(1) The question “how much water should we drink everyday?”- has varying answers and depends on many factors.
(2) Lack of water can lead to dehydration, a condition that occurs when you don't have enough water in your body to carry out normal functions. Even mild dehydration can drain your energy and make you tired.
(3) The Institute of Medicine has determined that for healthy adults living in temperate countries - an adequate intake (AI) for men is roughly 3 liters (about 13 cups) of total beverages a day. The AI for women is 2.2 liters (about 9 cups) of total beverages a day.
(4) The rule that says “Drink eight 8-ounce glasses of water a day” is not supported by hard evidence and should be rephrased by “Drink at least eight 8-ounce glasses of fluid a day”.
(5) Total water intake should be modified depending on how active you are, the climate you live in, your health status, and if you're pregnant or breast-feeding.
(6) To ward off dehydration and make sure your body has the fluids it needs, make water your beverage of choice. It's also a good idea to: (a) Drink a glass of water or other calorie-free or low-calorie beverage with each meal and between each meal and (b) Drink water before, during and after exercise.
While running and mountain biking, it is therefore advisable to carry water with you. In bikes, there are available “water bottle cages” and for runners various types of “hydration belts” are for sale to ensure that you are hydrated while conquering that road or terrain.