The generally-high microbiological and chemical quality of groundwater, abstracted from springheads and waterwells, has been vital for human survival, health and well-being for time immemorial. This is attributable to the self-purification capacity of subsoil profiles and the long subsurface residence times of groundwater systems.
However, potential groundwater quality problems can arise in a number of ways:
- Natural contamination by trace elements dissolved locally from subsurface strata
- In karstic aquifer systems, rapid flow and connection to polluted surface water
- Poorly-constructed waterwells allowing ingress of animal contamination and pump fuel oils
- Intensive agricultural land-use with the leaching of plant nutrients and some pesticides
- Inappropriate in-situ sanitation arrangements and wastewater disposal in urban areas
- Leakages of industrial chemicals and hydrocarbon fuels from pipelines and storage tanks
The diversity of this suite of potential quality problems means that all groundwater sources used for potable water-supply require quality surveillance, coupled with systematic survey and assessment of potential pollution vulnerability and actual pollution hazard for those sources of larger volume. The actions that can be taken by water-service utilities, rural water-supply agencies and others to mitigate the risks are equally diverse, and the principal measures are listed below.