Water intake from all sources is the issue, balancing that lost through respiration, perspiration, urine, and the colon. Urine color is the easiest, least expensive, lease invasive, most accurate way to judge for yourself how you're doing. The principle issue for us long term is our lack of reserve nephron mass if we get into a situation hazardous to our nephrons. Whether infection, hypertension, cancer, trauma, crystals due to dehydration or diet, or another of the amazing number of ways we've learned that kidneys can suffer, we have half the mass we might otherwise at our age, all in one place. Getting enough water so that no crystals fall out of solution in our blood and slice up our nephrons is a simple, daily thoughtfulness we give ourselves. Best wishes.