Here is a snippet from an article found on WebMD’s web site

How Much Water Do You Need?

How can you know if you’re getting enough water to keep your metabolism cranking at peak efficiency and your digestive system functioning? The formula used to be “one size fits all” — eight 8-ounce glasses of water a day. But that’s changed, experts say.
“It depends on your size and weight, and also on your activity level and where you live,” Nessler says. “In general, you should try to drink between half an ounce and an ounce of water for each pound you weigh, every day.” For example, if you weigh 150 pounds, that would be 75 to 150 ounces of water a day. If you’re living in a hot climate and exercising a lot, you’d be on the higher end of that range; if you’re in a cooler climate and mostly sedentary, you’d need less.
I am going to start measuring how much water I drink each day.  Today I weigh about 190 pounds. My plan is to drink about 95 to 190 ounces or about 3 to 5 liters per day.  I will be using my Nathan trail running pack to carry my water around with me at work and when I am doing chores at home.