Lower Mainland Region EPD

Water Quality Trend Monitoring in the Lower Mainland

Water quality trend monitoring is used to detect subtle changes over time that may result from an ongoing activity or land-use within the catchment area of the watercourse. Historically, water quality monitoring consisted of discrete (or ‘grab’) sampling, that is, a single sample is collected at a specific time and location and sent to a laboratory for analysis. As significant water quality changes can occur over very short time periods in developed drainages (largely in response to precipitation events), discrete sampling can miss transient events that may result in significant changes in water quality (Figure 1). As Figure 1 demonstrates, water quality data must be collected frequently to accurately detect changes in water quality, accordingly, discrete sampling is limited for trend detecting.

Figure 1. Comparison of turbidity measurements taken at 15 minute
and 7 day intervals between October 1, 2003 (1000 hrs PST) and
October 29, 2003 (1000 PST) at Millionaire Creek in Maple Ridge BC.

Advances in water quality monitoring technologies have resulted in the development of automated, stand-alone water quality monitors that are capable of measuring water quality parameters with a high degree of accuracy at user-defined sampling intervals as short as 1 second. Automated monitors, such as a Hydrolab® DataSonde 4a (Figures 2 & 3), can measure key water quality parameters (e.g. temperature, pH, specific conductivity, dissolved oxygen, turbidity and depth) that provide valuable information used in the assessment of water quality trends. The RISC Continuous Water Quality Sampling Programs: Operating Procedures are used to run the automated water quality monitors.

In 2001, the Lower Mainland Region Environmental Quality Section (LMREQS) commenced a surface water quality trend monitoring program (Trend Monitoring Program). Trend monitoring generally involves taking water quality measurements at regular time intervals (every 15 minutes for the LMREQS automated monitors) over a long-term period and analyzing the resultant data set to identify trends in water quality. Trend detection typically requires years of monitoring with the length of time dependant on factors such as the type of water body being monitored, the frequency of data collection, and changes in adjacent land uses. The objective of the regional Trend Monitoring Program is to assess impacts of non-point source pollution (a non-point source pollutant enters the receiving environment from a diffuse source that is not easily identifiable, e.g. storm water runoff, atmospheric deposition) on aquatic environments, and to identify trends in water quality (i.e. improving, unchanged, declining) at selected sites within the region. Trend monitoring sites were selected to collect water quality data at sites representative of a particular NPS source (e.g. urban development, agriculture). The Trend Monitoring Program also provides a measure of the efficacy of management strategies implemented to address NPS pollution and to facilitate better decision making regarding land use practices and the protection of surface water quality.

To date, trend monitoring sites have been established in Millionaire Creek (Maple Ridge, B.C.) (Figure 4) and Saar Creek (Abbotsford, B.C.) (Figure 5), River of Golden Dreams (Whistler, B.C.) (Figure 6) and Crabapple Creek (Whistler, BC) (Figure 7). Each regional trend monitoring site will operate for a minimum of 5 years before assessing the data and re-evaluating the need to continue monitoring.as well as providing technical support to the cities of Coquitlam and Port Coquitlam which are commencing automated water quality monitoring on the Coquitlam River and Hyde Creek.

• A summary of automated water quality data collected from Millionaire Creek from October 2001 to December 2003 is available here (PDF/969 KB/33 pages) - June 2004.
• A summary of historical water quality data from Sumas River, including Saar Creek, is available here - February 2005.
• A summary of water quality data collected from the Whistler Valley, including the River of Golden Dreams (ROGD) and Crabapple Creek, is available here - November 2005.
• Magnitude-Duration Based Water Quality Objectives for Temperature and Turbidity in Millionaire Creek Summary Report is available here (PDF/1.02 MB/30 pages) - November 2005.
• Water Quality Objective Recommendations for Millionaire Creek, Maple Ridge, B.C. report is available here - November 2005.

Figure 6. Hydrolab® station (attached to piling) at the River of Golden Dreams, Whistler, B.C. The Highway 99 crossing is in the background (downstream of station).

Figure 7. Hydrolab® station at
Crabapple Creek, Whistler, B.C.

UPDATED: november 30, 2005