The approximate quantities of water needed per man per day are as follows: For drinking only (minimum) 3 pints; For a day's march and bivouac or one night camps (for drinking and cooking only) i gallon; Camp where no clothing is washed 3 gallons; Camp where clothing is washed 5 gallons; Fixed camp where water is piped 25-30 gallons. In fixed camps with piped water supply, the number of gallons required is computed as follows: Drinking i, Cooking 2, Ablutions 2, Laundry 8, Shower 5, Water closet 6. The quantity of water required per horse or mule per day is from 6 to 10 gallons on the march or in camp, but in hot or dry weather this is sometimes increased to 15 gallons. Mules need less water as a rule than horses, and 6 gallons usually will suffice. To estimate the quantity of water yielded by a stream, the following formula is used: B X D X V X 10,800 = gallons in 24 hours. In this formula, B is the breadth of the stream; D is the average depth; V is the average velocity. This average velocity is four-fifths of the surface velocity, which is determined by noting the time that it takes for a floating stick or chip to traverse a measured length of the stream. The available output of a stream is increased by constructing dams. A gallon of water weighs 8 lbs. 3 ozs., and contains 231 cubic inches. A cubic foot of water weighs 62½ lbs. and contains 7½ gallons. The capacity of a cylindrical vessel in gallons is the product reached by squaring the diameter in inches, and multiplying this product by the length in inches, and by the fraction 0.0034. The quantity yielded by a well is estimated by rapidly lowering its surface by a measured depth, and noting the time it takes for it to refill. The volume of water in this space in cubic feet is the product of this depth by three-fourths of the square of the diameter, all in feet.
<Callout type="important" title="Critical Water Needs">Understanding the daily water requirements per person and animal is crucial for survival planning.</Callout> The purest water is rainwater. It always carries some slight constituents and impurities of the atmosphere, especially coal, sand, coal dust, and a minute quantity of organic matter including a few bacteria. Rainwater is highly aerated, wholesome, and palatable. It is very soft, an excellent solvent of soap, well suited for washing and cooking purposes.
<Callout type="gear" title="Rain Collection">In the field in the tropics, rainwater can be collected using troughs made from split bamboo.</Callout> The output of a spring may be increased by digging it out and lining it with wattle-work, an empty box or barrel from which both top and bottom have been removed, or by brick and stone. Surface drainage is kept off by a trench or a rim of clay.
<Callout type="risk" title="Pollution Risk">Streams draining inhabited areas should always be considered unsafe for drinking purposes until purified.</Callout> The most active biological elements in water purification are the nitrifying bacteria, which break up organic matter into simpler bodies. Their action is increased by falls and rapids which favor oxidation.
Wells were formerly classified as shallow or deep, but this standard is now discarded. The most important elements in determining the purity of well water are: 1) Whether it traverses an impermeable stratum; 2) Whether in chalk or limestone formation a fissure conducts into it deleterious material from some neighboring or distant point.
<Callout type="tip" title="Fluorescin Test">The fluorescin method can be used to detect drainage from sources of contamination into wells.</Callout> The diseases caused by polluted water are mentioned in the chapter on transmissible diseases. Protection of water is essential, and examination of water should be conducted rigorously.
Water may be purified by boiling, filtration, chemicals, and ultra-violet light.
Key Takeaways
- Understanding daily water requirements is crucial for planning in various environments.
- Rainwater collection can provide a pure source of drinking and cooking water.
- Streams draining inhabited areas are often contaminated and require purification before use.
Practical Tips
- Use the fluorescin method to detect contamination from nearby sources into wells.
- Construct dams or increase spring output by digging and lining with appropriate materials.
Warnings & Risks
- Streams in inhabited areas should be considered unsafe for drinking without proper purification.
- Water from chalk or limestone formations may contain contaminants due to fissures leading to distant pollution points.
Modern Application
While the historical context of this chapter is set during World War I, its principles remain highly relevant today. Understanding water requirements and sources, as well as methods for testing and purifying water, are crucial skills in modern survival scenarios. The techniques described here provide a foundational understanding that can be adapted with contemporary technologies.
Frequently Asked Questions
Q: What is the formula to estimate the quantity of water yielded by a stream?
The formula used is B X D X V X 10,800 = gallons in 24 hours. Here, B represents the breadth of the stream, D is the average depth, and V is the average velocity.
Q: How can one increase the output of a spring?
The output of a spring may be increased by digging it out and lining it with wattle-work, an empty box or barrel from which both top and bottom have been removed, or by brick and stone.
Q: What is the purpose of using the fluorescin method in water testing?
The fluorescin method can be used to detect drainage from sources of contamination into wells. It helps determine whether a well has been polluted from surface contaminants.