Source Assessment

Understanding, Assessing and Protecting Your Water Source

Every water supply system is unique, with different characteristics and needs. The first step in providing safe drinking water is to understand the water system including the water source. Source water is the raw untreated water that supplies the intake of your well or surface water source. Surface water sources include  a spring, creek, river or lake. Collecting information and data about your water source will allow you to identify potential concerns or hazards, assess their significance and put corrective measures in place.

The sustainability of your water source may be affected by natural events and human activities in watersheds. A community watershed is the drainage area (all or part) that is upslope of the lowest point from where water is diverted for human consumption. 

Changes in your watershed may impact the quality and quantity of your source water. If your water source is inadequate, finding a new and more dependable source can be expensive and time consuming. However, continuing to use an inadequate source can also present problems. If your existing source has poor water quality, you will be faced with the expense of installing additional and more complex treatment. The cost to maintain and service a water source that produces inadequate quantity should also be considered. Inadequate source water quantity can lead to customer complaints due to interruptions in supply. Customer complaints may also occur if you have poor source water quality due to changes to the aesthetic quality (i.e. odour, colour, taste, etc.) or microbial quality (i.e. health concerns). Poor source water quality carries an increased risk of waterborne illness, which can also result in customer complaints and civil lawsuits.

There are several ways the source water quality and quantity can be impacted. During periods of drought, the levels of surface and groundwater supplies can fall, reducing the quantity available to the water supplier. In times of water shortage, water conservation should be a priority. According to the Water Sustainability Act, all water supply wells in BC, including wells in First Nations communities, must be registered and licensed. This gives water suppliers first priority to draw water.

During spring freshet (when a river floods due to melting snow), water quality may decrease due to higher concentrations of pathogenic microbes carried by streams in the watershed, and increased turbidity (suspended matter in the water which causes it to be cloudy). While groundwater sources may sometimes be impacted, surface water quality is particularly impacted during spring freshet. 

Conducting a Source Assessment

The first step in your source assessment is determining (also referred to as ‘delineating’) your water source assessment area. How you define your assessment area will vary depending on your water source.

  • For a surface water intake, the assessment area would be the geographical catchment area (i.e. the contributing watershed) that drains into streams, which then flow to your source. However, this surface water assessment area may consist of a smaller subset of the contributing watershed if it is too large to reasonably assess and the risks do not seem to be high. Within this surface water intake assessment area, there should be an “intake protection zone” of at least 100 metres radius around the intake.

  • For a well, the assessment area would be the well capture zone plus a well protection zone of at least 100 metres radius around the well. The capture zone is the land area corresponding to the portion of the aquifer that contributes water (the well recharge area) to the well. A well’s delineated assessment area may include additional areas; such as for groundwater at risk of pathogens (GARP) or GARP-viruses only. Where appropriate, the well assessment area could also include areas for distant aquifer recharge areas.

  • For a spring, you would use a similar approach to the well assessment area with an intake protection zone of 100 metres radius around the spring. 

An understanding of the hydrogeologic setting is required to estimate the location and size of a well capture zone or a spring capture zone.This should be conducted before delineating the source area and assessment area. A hydrogeologist can help with this part of your source assessment.