2. Determining Water Needs
Minimum water needs vary with each situation but increase markedly with higher air temperatures and increased physical activity. In general, the following quantities of water will meet minimum needs.
Simplified table of basic survival water needs
Survival needs:water intake(drinking and food)
Depends on the climate and individual physiology
6 liters per day
Depends on social and cultural norms
Basic cooking needs
6 liters per day
Depends on food type and social, as well as
Total individual water needs
15 liters per day
Feeding Centers 30 L/inpatient/day
Health Centers 40-60 L/inpatient/day
Table III-1 contains figures on the water needs of large groups of DPs. Additional water may be needed for livestock, sanitation facilities, other community services, and irrigation. Cattle need 20-40 L of water daily; donkeys, mules, and horses need 10-40 L; camels need 15-50 L; and small stock require 5 L. Water will also be a factor in deciding on a sanitation system and will influence the design of latrines, clothes, washing and bathing areas, and drainage ditches. Water may also be needed for the irrigation of food crops by the displaced people. During the initial stages of an emergency, wastewater may be the only type of water available for irrigation, but it can often suffice for small vegetable patches if appropriate health-related precautions are considered. Large-scale irrigation is a matter for expert advice and therefore not addressed here. If possible, however, water sources for large-scale irrigation should be identified at an early stage.
Care should be taken to avoid pollution or depletion of scarce water sources by livestock; the more accessible the supply, the greater the consumption by animals.
Table III-1. Water Needs for Displaced People (in mL)
Formula: 15 L per person per day x no. of people x days = L
An insufficient quantity of water can have many health consequences. Proper supplementary and therapeutic feeding programs are impossible unless sufficient water is available for preparation of food and basic hygiene. When supplies diminish, clothes cannot be washed, personal hygiene suffers, cooking utensils cannot be properly cleaned, food cannot be adequately prepared, and in most extreme cases, the direct intake of water becomes insufficient to replace fluids lost from the body. Severe water reduction is also associated with an increased incidence of diarrheal diseases and the sometimes fatal dehydration associated with them; parasitic, fungal, and other skin diseases; and eye infections. Even individuals who have traditionally lived on less than the normally recommended amount of water, such as nomads, will require more in a DP community because of crowding and other environmental factors.
Water must be safe to drink. Although water may look safe, it may be polluted and contain microbiological organisms, or pathogens, that cause diseases.
Diseases transmitted by the fecal-oral route may be either "waterborne" or "water-washed." Waterborne fecal-oral diseases are transmitted by drinking water contaminated by feces. Because a disease is capable of being transmitted by a waterborne route, this term does not necessarily describe its usual or only means or transmission. Water-washed fecal-oral diseases are transmitted by ingesting feces through various pathways, including food, person-to-person contact, and water contaminated with hands soiled by fecal material. Water-washed fecal-oral diseases are diseases that can be impacted by an increase in available safe water for washing and personal hygiene. Hand washing is particularly important in the prevention of water-washed fecal-oral diseases. Other water-washed diseases of significance are trachoma and various skin diseases. These diseases are not transmitted by fecal-oral routes. They are best prevented by ensuring an adequate quantity of safe water for personal hygiene.
Water used for drinking needs to be of high quality. Water used for washing or personal hygiene can be of lower quality but should be available in greater quantities. Overall, a large quantity of reasonably safe water is preferable to a smaller amount of very pure water. The most serious threat to the safety of a water supply is contamination by human or animal feces. Protecting a water source from pollution is better than providing treatment for pathogen removal. Once contaminated, it may be difficult to adequately purify water under emergency conditions.
Where drinking water is scarce, brackish water, or even salt water, may be used for domestic hygiene.
New water supplies should be tested for microbiological contamination before use to determine the safety of the water. Existing supplies should be tested periodically, and immediately after an outbreak of any waterborne disease. In most situations, drinking water should be disinfected before distribution. Sanitary inspections of water sources are extremely important. The source of the water, protection of the water point, location of the source in relation to defecation areas, and protection of the water during transport and storage must be considered. A thorough sanitary inspection will often make it possible to determine that the water is polluted or likely to be polluted, and may make more complex bacteriological analyses unnecessary.
The most widely used microbiological tests detect fecal coliform bacteria, which are key indicators of fecal contamination. Tests for fecal coliforms can be performed in the laboratory or with portable field kits. The presence of fecal coliform bacteria indicates that the water has been contaminated by feces of humans or other warm-blooded animals. Some fecal coliform tests merely indicate the presence or absence of fecal coliform organisms. Other tests provide an indication of the concentration of fecal coliforms, expressed as the number of fecal coliforms per 100 mL of water.
Often, "Escherichia coli (E. coli)" is used interchangeably with "fecal coliforms." E. coli organisms represent approximately 90 percent of all fecal organisms. Testing for fecal streptococci is less frequently used as an indicator of fecal contamination.
Use table III-2 as a rough guide to the safety of potential water supplies. Sphere Guidelines, which provide minimum standards in disaster response, recommend that raw water supplies contain 10 or fewer fecal coliforms per 100 mL. As discussed below, there should not be any fecal coliforms present in properly disinfected water supplies. In certain situations, a water source (e.g., a properly protected well) can be used with a reasonable degree of safety without disinfection. Careful consideration, however, must be given before deciding to use water sources that have not been disinfected.
Table III-2. Fecal Coliform as an Indicator of Water Quality and Safety
Fecal Coliforms per 100 mL
More than 1,000
In cases where water is disinfected by chlorination, bacteriological testing is neither necessary nor appropriate. Chlorinated sources should be tested for the presence of residual chlorine. The presence of residual chlorine at a minimum of approximately 0.2 mg/L at the distribution point where people take water indicates that essentially all bacteria and viruses have been killed, and that the water is no longer contaminated with fecal or other organic matter. The chlorine residual should not be greater than 0.6 mg/L or the taste of the chorine will not be acceptable. See also the section below, "Chemical Disinfection," on the treatment of water with chemical disinfectants.
Water stored in tanks and tanker trucks should also be tested periodically. Appropriate sanitation and hygiene measures should be taken to protect the water between collection and use.
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