While it's necessary to keep the body hydrated, it's not necessary to drink 80 oz of water/day. Both my urologist and primary care physicians say that the old stand by of 64 oz/day isn't necessary as long as the body is not allowed to dehydrate.
Too much water can also be toxic.
Drink water. You need at least 80 fl oz of water daily. And thats with no exercise. So someone active should be drinkong double. It seems like alot yes but is necissary
A lot of things might cause that, but one that comes readily to mind is that your blood sugar is dropping too low.