Water in natural disasters and supply failures

The drinking-water supply is a chain: water is abstracted, treated, pumped into reservoirs and distributed through pipes. In disasters several links often fail at once. Without power, pumps and pressure-boosting systems stop, and on higher floors in particular no water arrives any more. Broken pipes can draw dirt and sewage into the network, and floods can wash sewage into wells and facilities.

Water utilities and authorities respond with two kinds of notice. A boil-water notice is issued when contamination with pathogens cannot be ruled out – boiling then protects you. A do-not-use notice is issued when chemical contamination is involved. Then boiling does not help, and you need water from another source.

Your own stock bridges the time until the authorities provide water at distribution points or the supply is safe again. In large-scale disasters, help cannot reach everyone everywhere at the same moment – which is why authorities such as Germany’s BBK recommend keeping a stock.

Base the amount on your own authority’s recommendation, as it differs between countries. Germany’s BBK gives around two litres per person per day for drinking and cooking in emergency preparedness and recommends a stock for several days. Plan an extra reserve: for children, sick people, pets, hot weather and a minimum of hygiene.

The simplest option is bought, sealed bottled water, because it keeps for a long time and you only need to watch the best-before date. Tap water you bottle yourself needs clean, food-grade containers and has to be renewed regularly. Store the stock somewhere cool and dark, away from chemicals, paints or fuels.

When an event is forecast – a storm or flood, for example – you can additionally fill clean containers with tap water while it is still considered safe. A filled bathtub or buckets provide utility water for flushing the toilet and rough cleaning. This water is not drinking water.

Flood water usually contains sewage, fuels and chemicals. Do not drink it, do not use it for brushing teeth or cooking, and avoid contact as far as possible. Boiling does not make flood water safe either, because it does not help against chemicals.

A boil-water notice does not only apply to your drinking glass. It also covers brushing teeth, ice cubes, washing fruit and vegetables that are eaten raw, and preparing baby food. Always follow your water utility’s exact instructions – including on flushing pipes after a notice has been lifted.

Stoves, grills and generators produce carbon monoxide. This gas is invisible and odourless and can kill in enclosed spaces. So run them only outdoors – never in living spaces, garages, basements or tents. If you get a headache, dizziness or nausea near such devices, go into fresh air immediately and call the local emergency number (112 in the EU).

Long power cut: pumps and water heaters can fail, and without power you may no longer be able to boil water. Then the stock and a safe way of cooking outdoors become more important. A battery or crank radio helps you receive official notices when the internet and mobile network are disrupted.

Earthquake or pipe damage: when pipes are broken, dirt can enter the network even if water still comes out of the tap. Until it is cleared, use tap water only as the authorities instruct.

Flood: here several dangers come together – contaminated tap water, flooded wells and the flood water itself. Only use your own wells that were flooded once they have been tested or the authorities allow it. If no safe water is available and chemicals are not a concern, you can clarify cloudy water and then boil it or disinfect it chemically according to instructions.

Build the stock in quiet times, not once the crisis has begun – by then shops are often sold out. Write the date on the containers and set a fixed date each year to check and renew the stock. Expired bottled water can be used up for cooking or watering plants and replaced.

Divide the stock by purpose in your mind: safe water first for drinking and preparing food, utility water for the toilet and rough cleaning. Talk with everyone in the household about where the stock is kept and what a boil-water notice and a do-not-use notice mean. That way everyone can act calmly and correctly in an emergency.