The quality of raw water is a key element when selecting a source for any drinking water supply system.
Water use, land use and polluting human activity in the catchment area all have significant impacts on
surface and groundwater quality, and thus the level and complexity of treatment plant necessary to
ensure that the water leaving the works is safe and acceptable to consumers.
Understanding catchment characteristics and/or activities potentially impacting on raw water quality and
availability is thus of paramount importance to ensuring drinking water safety. Protection of raw water
sources should be seen as the first, and often the most important, barrier to prevent microbial, chemical
and radiological contamination of drinking water.
The development of a catchment WSP based on risk assessment and management procedures, is very
dependent on the quality and quantity of relevant information available. Particular effort is required to
collect information on catchment characteristics (e.g. geology, hydrology, meteorology, land use,
competing water uses), surface water bodies (e.g. flow rate, water quality and seasonality) and
groundwater (e.g. aquifer flow rate, flow direction and aquifer vulnerability to pollution).
This chapter sets some of the factors underpinning catchment management, provides advice on
developing a catchment WSP in conjunction with external stakeholders, describes methodologies for
assessing and managing both surface and groundwater catchments and briefly summarises common
catchment risks and how they might be mitigated.