Lowe's daily goal is 100 ounces, more on the five days she attends exercise classes.

"I still have coffee in the morning and juice or iced tea in the afternoon," she said. "But I quit drinking soda."

Thanks to lemon slices and a carbonator she shares with co-workers, her office drinking water is jazzed with "bubbles and taste, which is better than the sugar and calories you get in soda."

Dry skin is her reminder that she is not drinking enough water, Lowe said. "Also, if I don't drink enough, I think I'm hungry after I've already eaten, but I'm just thirsty," she said. "If I drink some water, I'm not tempted to snack when I shouldn't."

Senior citizens have an added problem, Burke said.

"As you get older, you lose your ability to know when you're thirsty," she said. "So seniors should remind themselves to drink water and other healthy drinks."

It helps to keep a diet diary, Burke said.

"If you write down what you drink for a week at work and at home, because it will be different, you may be surprised how little water you actually drink," she said.

As for Nisi, she is determined to increase her water intake.

"I quit coffee," she said. "That helped a lot. I know I have more energy when I drink more water. So, it's a goal."

The study analyzed the drinking habits of 3,397 adults who participated in the National Cancer Institute's Food Attitudes and Behaviors Survey. It was published in the April 11 issue of the CDC's journal, Preventing Chronic Disease.