Water saving stratege
A water ration of as little as a pint per day has allowed life raft survivors to live for weeks, but a more realistic figure is 1 gallon per person per day for survival. 4 gallons per person/day will allow personal hygiene, washing of dishes, counter tops, etc. 5 to 12 gallons per day would be needed for a conventional toilet, or 1/2 to two gallons for a pour flush latrine. For short-term emergencies, it will probably be more practical to store paper plates and utensils, and minimize food preparation, than to attempt to store more water.
In addition to stored water, there is quite a bit of water trapped in the piping of the average home. If the municipal water system was not contaminated before you shut the water off to your house, this water is still fit for consumption without treatment. To collect this water, open the lowest faucet in the system, and allow air into the system from a second faucet. Depending on the diameter of the piping, you may want to open every other faucet, to make sure all of the water is drained. This procedure will usually only drain the cold water side, the hot-water side will have to be drained from the water heater. Again, open all of the faucets to let air into the system, and be prepared to collect any water that comes out when the first faucet is opened. Toilet tanks (not the bowls) represent another source of water if a toilet bowl cleaner is not used in the tank.
Patton Turner. Water Treatment FAQ. Available from URL:http://athagan.members.atlantic.net/PFSFAQ/Water_TreatmentFAQ-v2.2.html
Without water, a human continue to sweat unabatedly until the water deficit excedds 10% of the body weight, when collapse occurs. With a water deficit of 12% a human is unable to swallow water, and a death occurs when the water deficit reaches about 15% to 20%. Few people can survive more than a day or two in a desert without water.
The longest reported voyage withoura supply of fresh water lasted 15 days.
p147 water-conservatoin stratege
Survivors should consume no water in the first 24 hours because the body's reserve should be able to cope in the early stages. Much of the water drunk in this period will be excreted wastefully as urine. Thereafter, survivors should restrict intake to aboud 500 milliliters (just over a pint) a day. Protein should be avoided. Protein metabolism requires water to excrete the urea.
----Hickman CP, Roberts LS, Larson A. Homeostasis: Osmotic Regulation, Excretion, and Temperature Regulation. In: Biology of Animals, 7ed. McGraw-Hill, Boston 1998;170
-- Essentials of sea survival
Food saving stratege
If water is in short supply it is important not to eat anything because it increases your water needs to digest the food.
Most people today can go 3 weeks without eating.
Apply the following rules as soon as you realize that you are isolated. Human have been known to live for more than a month withour food. Thus, take time.
1, Inventory your rations and water. Estimate the length of time you will be on your own.
2, Divede your food; 2/3 for the first half of yuor isolation and 1/3 for the second half.
3, Avoid dry, starchy, and highly favored foods and meats if you have less than one quart of water for each day. Eating make you thirsty. Eat food high in carbohydrate; hard candy or fruit bars.
4. Keep sternuous work to minimum. The less work, the less food and water you require.
5, Eat regulary. Plan one good meal each day. Cooking makes food safer, more digestable, and palatable.
6, Look out for wild food; plants, insects, fish, or reptiles.
-------------Department of the Army. FM21-76 Field Manual;Survival. 1970