West Coast Natural Resource Region Low Streamflow Report

7 Day Average Streamflow Percentiles

7 Day average streamflow percentiles compare current stream flows (averaged over the last seven days) to the same seven day period in a site’s historic record. Streamflows are averaged over seven days to minimize the impact of short term fluctuations, and gives a better representation of the overall trend in streamflow. Percentiles give an indication of how likely a seven day streamflow value is; for example, the 50th percentile represents normal conditions, where a streamflow percentile of 10 indicates that this value has occurred only 10% of the time within the history of the site. Data is sourced from real-time and historic Water Survey of Canada data.

In general, a streamflow value of:

• The highest ever measured for the day of year is considered “High”
• Greater than the 90th percentile is considered “Much Above Normal”
• Between 75th percentile and 90th percentile is considered “Above Normal”
• Between 25th and 75th percentiles is considered “Normal”
• Less than the 25 percentile is considered “Below Normal”
• Less than 10 percentile is considered “Much Below Normal”
• The lowest ever measured for the day of year is considered “Low”

The below map shows percentiles using both a rolling average over the last seven days of discharge as well as mean discharge over the last 24 hours.

Map data was updated on 03 April 2025, 03:36 AM.

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Streamflow - Seven Day Percentiles

Streamflow - Last 24 Hour Percentiles

BC Provincial Drought Polygons

7 Day Streamflow Percentile Colours

Not ranked
Low
Much below normal (<10)
Below Normal (10-24)
Normal (25-75)
Above normal (76-90)
Much above normal (>90)
High

Long-Term Mean Annual Discharge (% LT MAD)

Environmental flow needs for fish during the summer will range from juvenile rearing flows near 10-20% (preferred) Long-Term Mean Annual Discharge (LT MAD) to adult salmon/char passage flows (>20% LT MAD) required prior to spawning. Sub-standard flows (<10% LT MAD) can affect fish populations by reducing the area and quality of riffle habitats that generate fish food and aeration. Flows nearing 5% LT MAD are considered sub-optimal for fish rearing and migration, indicate a degradation of instream habitat and may require restrictions on water use. A map of realtime streamflow data can be accessed at the BC River Forecast Centre website. LT MAD values were calculated by dividing the 7 day mean discharge by the mean annual discharge (MAD) calculated from historic data. MAD values were calculated for stations with at least 5 years of data in the historic record only from years with complete data using the R package fasstr.

Map data was updated on 03 April 2025, 03:36 AM.

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All sites - % MAD

Sites with % MAD < 10%

BC Provincial Drought Polygons

% MAD

Not ranked
<1%
1 to 5%
5 to 10%
10 to 20%
20 to 100%
> 100%

Maximum Daily Water Temperature

The recommended mean weekly maximum temperature (which is the mean of the max daily temperatures from the last seven days) for the protection of all fish species should not exceed 20 degrees C and the maximum daily temperature should not exceed 23degrees C. Reaching either one of these thresholds may trigger fisheries closures and water use restrictions within the affected watersheds. Only a small subset of stations from the Water Survey of Canada collect temperature data in addition to streamflow data; thus the number of sites shown here is much smaller than for streamflow. Some provincially run hydrometric stations may also collect temperature data and may be shown.

Map data was updated on 03 April 2025, 03:36 AM.

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All sites - 7 Day Mean Max Daily Temp

>20 Deg C - 7 Day Mean Max Daily Temp

>23 Deg C - 7 Day Mean Max Daily Temp

>23 Deg C - Max Temp (Last 7 Days)

BC Provincial Drought Polygons

7 Day Max Daily Temp

Not ranked
<16 degC
16 to 20
20 to 23
> or equal to 23

Hydrometric Statistical Summary for All WSC Stations

The following table contains all of the drought-relevant statistics for all stations within the region.

These statistics include:

• Last 24 hour Discharge: Mean discharge taken over the last 24 hours (in m³/s)
• Percentile - Last 24 Hour Discharge: Percentile of the average discharge over the last 24 hours
• Latest 7 Day Discharge: Rolling 7-day average of daily mean discharge for today’s date. All 7 day means are calculated based on the past 7 days.
• Percentile - 7 Day Discharge: Percentile of the rolling 7 day average of daily mean discharge measurements to the 7 day rolling mean of the historical daily values.
• Historic Mean 7 Day Discharge: Value of the rolling 7-day averaged daily mean discharge value for today’s date, calculated using the station’s historic data (in m³/s).
• Percent of Daily Mean 7 Day Discharge: Percent of the 7 Day Discharge for today’s date compared to the mean 7 Day Discharge value for today’s date within the historic record of the station (i.e., Latest 7 Day Discharge/Historic Mean 7 Day Discharge *100)
• Historic Median 7 Day Discharge: Value of the rolling 7-day averaged daily median discharge value for today’s date, calculated using the station’s historic data (in m³/s).
• Percent of Daily Median 7 Day Discharge: Percent of the 7 Day Discharge for today’s date compared to the median 7 Day Discharge value for today’s date within the historic record of the station (i.e., Latest 7 Day Discharge/Historic Median 7 Day Discharge *100).
• Historic Min 7 Day Discharge: The minimum 7 day averaged mean daily discharge value for today’s date within the historic record (in m³/s).
• MAD (m³/s) and % MAD: Flow needs during the summer will range from juvenile rearing flows near 10-20% (preferred) MAD to adult salmon/char passage flows (>20% MAD) required prior to spawning. Sub-standard flows (<10% MAD) can affect fish populations by reducing the area and quality of riffle habitats that generate fish food and aeration. Flows nearing 5% MAD are considered sub-optimal for fish rearing and migration, indicate a degradation of instream habitat and may require restrictions on water use.
• Mean Max Daily Temp (last 7 days; deg C): Mean of the max daily temperatures from the past week. Temperatures greater than 20 degrees C can indicate increased stress on fish populations.
• Max temp over last 24 hours (degC): Maximum temperature over the last 24 hours (degree C).
• Dates above 23 degC and 20 degC in last 7 days: Dates from the past week that the stream temperature has gone beyond either 20 or 23 degrees C.

Regulation Status refers to whether flows are natural or regulated by human activities such as dams; this (as well as the Basin Area) were determined by the Water Survey of Canada.

Data was updated on 03 April 2025, 03:36 AM.