Despite a major river cutting through the Canyon, natural water sources are sparse and mostly seasonal. Thankfully, there are numerous non-natural water sources along the RRR route—some are year-round while others are turned on seasonally. Note that occasionally the pipe system fails, in which case these non-natural water sources will not be reliable—there will probably be bulletins posted in key locations if this occurs. For the sake of space, I have created a separate PDF document that provides water charts for each of the 6 route options.
There are two parts to determining optimal hydration—that is, carrying exactly enough to stay hydrated, but no more. One part is knowing the locations of water sources and the distances between them (see paragraph above). The other part is knowing your rate of water use, which is a function of your physical output and the environmental conditions (namely, ambient temperature and sunlight exposure). If you make the effort to determine your rate of water use during training efforts, it is very valuable information. Personally, when I am hiking, I find that I need a maximum of 1 liter per hour—like when I’m on a good climb through a shade-less desert landscape with 90-degree temperatures. As my effort and/or the temperatures mellow out, I need less water—my average consumption in typical 3-season conditions is about 1 liter for every 2-3 hours.
If you know what works for you during this type of endeavor, go for it. I carried drink mixes and gels—they go down easy, require minimal digestive effort, and are tolerable for a day. I found that 400 calories every 2 hours was sufficient, after starting with a moderate 800-calorie breakfast of energy bars. When I reached the top, I had a 1-lb slab of protein-rich honey ham waiting for me in the car, which I think helped tremendously with my quick recovery. (I was slightly achy and stiff the next day, but felt good enough for a 30-minute run.)