It is really important that you keep hydrated during the MC. If your urine is yellow then that is a pretty clear indicator that you are not consuming enough water. A good rule of thumb is that you should consume half as many ounces as your weight in pounds (eg. if you weigh 200 pounds you should consume at least 100 ounces a day). The color of your urine is the best way to tell though. If you are dehydrated, your body will try to pull water out of the salt water flush and the resulting overload of salt in your system can have nasty side effects. There is a good post related to this from a week or so ago.