Core calculation
The evacuation center houses
600 families, and each family averages
5 members. Multiplying these gives
3,000 persons. The Sphere key indicator sets a minimum of
15 liters per person per day for drinking, cooking, and personal hygiene. Therefore, the daily water request is
3,000 × 15 = 45,000 liters per day.
The correct answer is 45,000 L/day, which represents the minimum quantity needed to meet basic survival and hygiene needs in a mass displacement setting.
Why this matters in disaster nursing
In a post-earthquake evacuation center, the public health nurse must estimate resource needs before shortages develop. Water is prioritized because inadequate supply rapidly leads to dehydration, poor hand hygiene, and outbreaks of diarrheal disease. The Sphere standard is a widely used humanitarian benchmark, and the
15 L/person/day figure is the minimum acceptable level for short-term survival; it does not include water for laundry, full bathing, or facility cleaning.
Watch out! Do not confuse the per-person daily minimum with a per-family or per-week figure. The problem gives families and members per family, so the first step is always to convert to total persons before multiplying by the daily per-person allocation.
Step-by-step reasoning for exam settings
| Step | Action | Result |
|---|
| 1 | Identify total evacuees: 600 families × 5 members | 3,000 persons |
| 2 | Apply Sphere minimum: 15 L/person/day | 15 L |
| 3 | Multiply total persons by daily allocation | 45,000 L/day |
Key point! The answer is a daily volume, not a total for the entire disaster period. If the question later asks for a 7-day supply, multiply
45,000 L by
7 to get
315,000 L.
Clinical and public health context
Water quantity is only one part of the Sphere water supply standard. The same standard also addresses water quality, access distance, and queueing time. In an evacuation center, the nurse should verify that water points are within
500 meters of shelters and that each tap serves no more than
250 people. However, the question asks only for the quantity calculation, so the numeric answer remains
45,000 L/day.
The provided reference materials do not address disaster water supply calculations, so no additional evidence from those abstracts is used here. The calculation follows the Sphere key indicator stated in the question stem.