Detective Freshwater Sources in Vancouver
Our Recreational Water Monitoring Reports from 2022 will be released soon. We wanted to take this opportunity to expand on some content in our Vancouver report.
“Our results indicate that there is an external water source entering False Creek, causing water quality results to waiver from the expected values for this environment”
Let’s take a deeper dive into what exactly that means.
What do these measurements mean for water quality?
If the water is very clean, the speed of the electrical current will be determined entirely from the salts in the water, therefore salinity and specific conductivity will be the same. If there is pollution in the water, there will be organic compounds as well as salts, making conductivity higher than salinity. This may indicate that there is some pollution in the waters around Vancouver, since the salinity is slightly higher than specific conductivity.
Why are all of the measurements so varied from month to month?
Variation in salinity, total dissolved solids, and specific conductivity changes is indicative of another type of water entering the system. This may be rainwater, river outflows (the Fraser River outflow sometimes can come all the way into False Creek), or it may be pollution from sewage or agriculture runoff.
Variations in all of the water quality parameters discussed in this section can be caused by rain, the Fraser River outflow, or pollution. So which is it?
We do not have E.coli data for this year, so unfortunately we cannot determine exactly when pollutants are entering the system. So we had a look at other freshwater sources to try to determine the freshwater sources.
Possible Source #1: The Fraser River Outflow
The image above shows the Fraser River outflow during a storm event. The image on the right shows the Fraser River outflow during a regular season. Have a look at False Creek! It is possible to identify that the fresh water from the Fraser River is only entering during extreme weather events.
Possible Source #2: Rain
Rain is certainly factoring into all of the water quality measurements. Let's look at this one water quality measurement at a time.
Dissolved oxygen: as the rain decreases, so does the available oxygen for fish
pH: as rain decreases, pH increases. This is expected as pH of saltwater is higher than freshwater
Specific conductivity and salinity: this is where it gets interesting. Because as freshwater enters the system, it is expected that salinity would decrease, but instead it tends to rise and fall with the rain.
Possible Source #3: Pollution
Combined Sewer Overflow events are mainly due to heavy periods of rain. It is possible to see that the rainwater is heavily affecting water quality measurements. We just have to ask ourselves if we think that False Creek would be so heavily affected by rainwater if it was just from rain going directly into the ocean without the influence of storm drains and sewage outflows? What is causing the variability with specific conductance and salinity measurements?
