Water is so abundant on this planet that many of us take it for granted. Water is almost everywhere - even in the air we breath in most places. In fact 60% of an adult humans body weight is water - we are sort of like animated water balloons you might say. However the playa is dry, and not dry like you might normally think of dry. It is dry to the point of desiccation and that is very dangerous to us walking water balloons. During the week of Burning Man expect the humidity to be zero, or very close to zero.
How Much To Bring
The general rule of thumb is to bring a minimum of 1 1/2 gallons (6.7 liters for you metric folks) per person per day. This would include a gallon for drinking and half a gallon for washing, cooking, etc... If you plan a more elaborate camp with a shower or other things that use water you will need even more.
The heat and dryness on the playa will suck you dry rapidly - you must stay hydrated. Start pounding back water the day before you arrive and don't stop until you are on your way home. Don't leave camp without a supply of water. I know this seems extreme but if you don't you will end up at the med tent with an IV drip in your arm (or worse).
Electrolytes are also needed to maintain health on the playa. My personal preference is to add Vitalyte powder to my water. They are also available in tablets or ready made drinks.
Don't Leave Home Without It
When traveling around Black Rock City you should always have a supply of water with you (yes even at night). My personal preference is a Camelback Mule - basically a cyclists backpack with a 100 ounce hydration bladder built in. It has a decent capacity of water as well as room to transport other necessities. You will see all sorts of personal water carriers, but camelbacks, Nalgene bottles, and canteens are the most popular. Generally 2 liters should be the minimum amount you carry
Water when mixed with caffeine (coffee, tea, some soda), or alcohol doesn't count towards your necessary daily intake. In fact it makes you need unadulterated water even more.
Caffeine is a diuretic - basically it will cause you excrete water from your body at an increased rate. It's a good idea to limit or eliminate caffeine from your diet at the burn.
Alcohol dehydrates the body's cells, even at night and when its cold. A popular rule of thumb is to drink at least twice as much water for each alcoholic drink - i.e. 4 ounce drink, minimum of 8 ounces of water - more is even better.
Dehydration can sneak up on you - especially if you like to party. One of the best defenses against it is to know the symptoms and always look out for those you are with. The following is quoted from the survival guide:
Dehydration can cause headaches, stomach cramps, abdominal pains, constipation, or flu-like symptoms. It exacerbates both heat-related and cold-related conditions (i.e. heat exhaustion and hypothermia), and makes it difficult for the body to mend itself. If someone you know complains of these symptoms, or shows signs of either severe overheating or (worse) a case of chills under the mid-day sun, get them to shade immediately and seek prompt medical help.
Although not a foolproof symptom - crankyness often is an early warning sign of impending dehydration.
Gray water is basically the generic term for water that has been used in cooking, washing, showering, brushing your teeth, and so on. It can't be dumped on the playa without first sterilizing it and spreading it out. There are two basic strategies for dealing with it. The easiest way is to just pack it back out with you. It can also be evaporated off but that gets much more involved.
Black water is the term used for water used in toilets and cannot be dumped on the playa at all. Generally this will only be a factor if you bring your own toilet - such as those in an RV or camper. There are trucks you can flag down to get your RV pumped out. In 2011 this cost 50.00 for small RVs, 60.00 for larger ones and they would empty both RV holding tanks (black and gray).
Water Is Heavy
Many people don't realize how heavy water is, but you need to factor that into your transport plans as well as the amount you are carrying around the Playa. One gallon of water weighs 8.34 pounds or for those who normally use the metric system, one liter weighs a kilo. So the minimum week supply of water for one person will weigh roughly 100 pounds (45.4 kilos).
Likewise with the water you carry around when out and about on the playa. Figure to start with it weighing roughly 4 1/2 pounds or 2 kilos, although as you drink it will weigh less over time. Because of this it's a pretty good idea to have a comfortable way to transport your water.