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< prev - next > Disaster response mitigation and rebuilding Emergency relief KnO 100648_Water Supply during emergencies (Printable PDF)
Water Access in Emergencies
Practical Action
Groundwater is water that fills natural openings in rock and sediment underground, with gravity
forcing its percolation through soil until it reaches the water table. The sections of rock that store
and transmit water are known as aquifers, whereas impermeable layers such as clay or bedrock
are known as aquicludes. Groundwater can be accessed by the following:
The water is often of much higher quality than surface water, due to the natural filtration
processes that rock and soil formations provide. Conversely, it is usually more expensive and time
consuming to access; understanding the geological nature of the terrain in an emergency situation
will assist in the construction of wells and boreholes, and/or the locating of springs. It is also
important to assess how much water is stored in an aquifer and what the ‘recharge’ (water
replenishment) rate is, in order to calculate a sustainable abstraction rate. Consult Engineering in
Emergencies and WEDC’s guide on Emergency Water Sources for more information.
Springs are an ideal source in an emergency, providing water that is likely to be of very high
quality that does not need pumping. Springs can occur at diffuse seepage areas, commonly found
at lower ground levels where gravity has taken water through various layers, or at point sources,
which are often found at faults between layers of aquifers and aquicludes. Aquifers can be
unconfined (atmospheric pressure) or confined (pressure great than atmospheric), and various
geological structures can force water to the surface. An example of this is shown below:
As described in the ‘Immediate Actions’ section, the protection of sources is essential to ensure a
sustainable supply; the following steps are commonly taken in order to protect a spring source:
1) Dig a drainage ditch above the
spring to divert possible rainwater
away from source.
2) Clear spring area, removing all
vegetation and providing good
drainage, but be careful not to
disturb surrounding ground
3) Fence area about 10m above and
around spring to control access.
Additionally, the construction of filter
systems can help to remove sediments
in the water. There are various methods
of construction, and the chosen
solution will be dependent primarily on
time and cost. A relatively simple
method is shown below:
Figure 9: Spring from a confined aquifer
Source: Davis, J. and Lambert, R. (2002)
Figure 10: Protection and filter
system for a point source spring
Source: Davis, J. and Lambert, R.