A source water assessment provides you with details on the hazards observed in your watershed, a risk ranking of the hazards, and a strategy covering how to improve or protect water quality before it enters the water system.
The assessment is the first part of a source protection plan (the second part is the response plan described in STEP 3), and is usually completed by a qualified professional under the guidance of the water supplier and TAC. The British Columbia Comprehensive Drinking Water Source-to-Tap Assessment Guideline outlines the process to follow for a source water assessment and the roles and responsibilities of participants and regulatory agencies in completing the assessment.
The Source-to-Tap Guideline includes eight modules. Modules 1, 2, 7 and 8 apply to source water assessments, and are described below.
Module 1: Delineate and characterize drinking water sources.
A description and assessment of natural features of the water source and source area of a water supply is completed. For surface water sources, the boundary of the source assessment area is ideally that of the catchment that drains to the intake, or it may be a more focused zone such as the immediate vicinity of the intake, within a time-of-travel to the intake or an arbitrary radius from the intake. Consider mapping areas of high vulnerability (TOOL 7). For groundwater sources, capture zones may be delineated using one or more of the following methods: 1) arbitrary fixed radius, 2) modified arbitrary fixed radius, 3) calculated fixed radius, 4) analytical equations, 5) hydrogeologic mapping, or 6) numerical modeling. The methods are described in Appendix 1G of the Source-to-Tap Guideline.
Module 2: Conduct contaminant source inventory.
A contaminant source inventory identifies and describes land uses, human activities, and other potential contaminant sources that could affect source water quality. Contaminants in water include substances that are physical (e.g., sediment), chemical (e.g., fuels, pesticides), or biological (e.g., pathogens). When these substances are not normally found in drinking water or exist in excess of natural concentrations and have the potential to impact the viability of a water supply system, they become an agent of harm and a hazard to drinking water. It is important to periodically re-evaluate and redefine potential contaminant sources given continued changes in the landscape from land-use, natural events, and climate.
Module 7: Characterize the risks from source to tap.
A risk level is assigned to each of the hazards identified in Modules 1-6 based on a matrix of likelihood to impact a system and magnitude of consequence. The primary strengths, weaknesses, major threats and key opportunities for significantly improving drinking water protection are assessed for the water system.
Module 8: Recommend and prioritize management actions.
The assessment team collectively identifies actions for each risk identified in Module 7. The recommendations include hazard(s) addressed, protective barriers enhanced, accountability and timelines for implementation. Priorities for source water protection are informed by the risk level of the hazards. Ideally, management actions should address hazards of very high and high risk first; however, implementation may be prioritized based on resource availability or ease of application.
A source water assessment template is provided. The issues identified and actions recommended in the assessment will be the foundation of the response plan you create in Step 3.
