Two main categories of water supply sources are generally noted, namely:
Surface water (water on the land surface that could include streams, rivers, lakes, dams) - Surface water is more vulnerable to human contamination than groundwater because of its direct exposure. Basic surface water quality problems are defined as those associated with particulate content, colour, taste, odour and microbiological content. They cause water quality problems such as high salt content, acid water, contamination by bacteria and pollution by toxic substances. A more effective way of increasing the quality of water may be to reduce the need for treatment in the first place. Preventing pollution from occurring in the water source by providing environmental sanitation, controlling erosion and restricting public access to the catchment of the water source can reduce the amount of contaminants that have to be removed from the water.
Groundwater (water contained within the geological formations accessed by springs, wells or boreholes) - Small communities in the developing world rely heavily on ground water sources and must manage them with limited resources. The survival of pathogens in groundwater systems is an important factor in determining quality of drinking water supplies. In undertaking assessment of risks to groundwater sources, identification of the most important factors in controlling contamination is essential. Such an assessment should incorporate sanitary inspection and water quality data and statistical models to assess the most important factors influencing contamination.
In addition to the above two general types, seawater and reclaimed wastewater have become sources of water in arid areas facing water shortages. In smaller communities, rain water harvesting is also often used.
Everyday organizations and individuals impact on source water quality. Major water quality problems in South Africa are as a result of wastewater from industry and mining, agricultural fertilizers, erosion, domestic waste and a lack of sanitation. Experience has shown that the better the raw water quality, the better and safer the final treated water. Therefore, in trying to obtain the best raw water quality available, source water protection should be a priority. The protection of drinking water source, selection of appropriate treatment methods, well protected distribution networks and appropriate quality monitoring are necessary in the maintenance of drinking water quality.
Further general information related to source water protection is contained within the following sections: