In selecting a water source, attention must be given to possible future developments that may influence the continued suitability of the source.
Other considerations include
Quantity (source capacity): The quantity of water should be sufficient to meet continuing demands taking into account daily and seasonal variations and projected growth in the size of the community being served.
Quality: The quality of raw water should meet the drinking water standards after appropriate treatment.
Protection: The watershed must be protected from pollution with human excreta, industrial discharge and agricultural run-off.
Feasibility: The source should be available at reasonable cost.
Treatability: The raw water should be treated adequately under locally prevailing conditions.
Potential new sources should be examined in the field by qualified and experienced sanitary surveyors and physical, bacteriological and chemical analysis should be carried out prior to final selection of the source. Such information is essential in order to define appropriate water treatment requirements and necessary pollution control measures to protect raw water resources. It is preferable to choose the source that requires the least treatment, is protected from contaminants originating from septic tanks, sewers, cesspools, sullage water and from contamination by users. Maintaining adequate residual chlorine levels in the distribution system is the most reliable indicator of protection against contamination resulting from cross-connection back siphonage, leaks etc.