The BC River Forecast Center has issued a Low Streamflow Advisory for Vancouver Island.
Snow pack conditions on Vancouver Island were at historic lows this past winter. Vancouver Island experienced an early onset of warm, spring-like conditions in March and warm temperatures and dry conditions have continued from late April through to the present.
The combination of extreme low snow packs, below normal precipitation and warmer than average temperatures has led to seasonally-low to extreme-low conditions in streams of Vancouver Island. Current flows are more typical of late-August conditions, with many rivers approaching, or already below, average annual low flow level. Most rivers across Vancouver Island are flowing at the 2nd to 5th percentile flows for this time of year (e.g., approximately 20-year to 50-year return period low flow).
Environment Canada forecasts less than 10 mm rainfall on Vancouver Island over the next 10 days and continued warmer-than-normal temperatures. With little rain and continued warm weather, coupled with negligible remaining snow melt runoff, it is expected streams will continue to decrease through to early July.
Within the Cowichan Region, the following streams are included in the advisory:
Extreme-low streamflow conditions
- Koksilah River at Cowichan Station (08HA003) is currently flowing at 0.14 m³/s, which is 13% of the median flow (1st percentile) and below the recorded minimum flow for this period of time.
Seasonally-low streamflow conditions
- Chemainus River near Westholme (08HA001) is currently flowing at 0.86 m³/s, which is 25% of the median flow (1st percentile) and just above the recorded minimum flow for the period of time.
Current streamflow for regulated streams
- Cowichan River near Duncan (08HA011) is currently flowing at 5.88 m³/s, which is 57% of the median flow (11thpercentile) and above the recorded minimum flow for the period of time. [Note: the flow in the Cowichan River is regulated by the weir at Lake Cowichan]