What are the reasons for a water shortage during a flood?

Question

Specifically, how does usable water become contaminated during a flood?

Answer 1

Floods usually stir up sediments and make water-flows more rapid so the turbidity of water increases.

(Turbidity= Suspended particles in the water)

Often these sediments can run-off from urban environments (just think of all the filth that can build up in streets) and then end up in our waterways. Also, agricultural residues can also be washed into waterways such as pesticides and faeces.

When water catchments have agriculture and urban areas within them, this can become a severe problem. A good catchment will be free of human land use and the riparian fringe of riverbanks free from land degradation (as this can often cause riverbanks to erode and add sediment into waterway)

Answer 2

Surface water sources become polluted with runoff from the flood heavy rains and runoff.

Answer 3

From a drinking point of view, the contamination is from:

overflowing sewage systems (gross)

dead animals and humans (grosser)

This increases E Coli and other harmful bacteria levels and can spread diseases such as typhoid.

Answer 4

Potable water is either stored in reservoirs, pulled from the water table (underground) or treated river water.

Runoff from a flood contains all sorts of contaminants (soil, chemicals, insecticides, fertilizers, etc.) that mix with the listed sources of water, making them unusable.