Add a column of daily water yields to a daily streamflow data set, in units of millimetres. Converts the discharge to a depth of water based on the upstream drainage basin area.

  values = Value,
  groups = STATION_NUMBER,



Data frame of daily data that contains columns of dates, flow values, and (optional) groups (e.g. station numbers). Leave blank or set to NULL if using station_number argument.


Name of column in data that contains numeric flow values, in units of cubic metres per second. Only required if values column name is not 'Value' (default). Leave blank if using station_number argument.


Name of column in data that contains unique identifiers for different data sets, if applicable. Only required if groups column name is not 'STATION_NUMBER'. Function will automatically group by a column named 'STATION_NUMBER' if present. Remove the 'STATION_NUMBER' column beforehand to remove this grouping. Leave blank if using station_number argument.


Character string vector of seven digit Water Survey of Canada station numbers (e.g. "08NM116") of which to extract daily streamflow data from a HYDAT database. Requires tidyhydat package and a HYDAT database. Leave blank if using data argument.


Upstream drainage basin area, in square kilometres, to apply to observations. Three options:

(1) Leave blank if groups is STATION_NUMBER with HYDAT station numbers to extract basin areas from HYDAT.

(2) A single numeric value to apply to all observations.

(3) List each basin area for each group/station in groups (can override HYDAT value if listed) as such c("08NM116" = 795, "08NM242" = 10). If group is not listed the HYDAT area will be applied if it exists, otherwise it will be NA.


A tibble data frame of the source data with an additional column:


daily water yield, in units of millimetres


# Run if HYDAT database has been downloaded (using tidyhydat::download_hydat())
if (file.exists(tidyhydat::hy_downloaded_db())) {

# Add a column of yields based on HYDAT basin area
add_daily_yield(station_number = "08NM116")
# Add a column of yields based on a custom basin area
add_daily_yield(station_number = "08NM116",
                basin_area = 800)
#> # A tibble: 23,079 × 6
#>    STATION_NUMBER Date       Parameter Value Symbol Yield_mm
#>    <chr>          <date>     <chr>     <dbl> <chr>     <dbl>
#>  1 08NM116        1949-04-01 Flow       1.13 E         0.122
#>  2 08NM116        1949-04-02 Flow       1.53 E         0.165
#>  3 08NM116        1949-04-03 Flow       2.07 E         0.224
#>  4 08NM116        1949-04-04 Flow       2.07 E         0.224
#>  5 08NM116        1949-04-05 Flow       2.21 E         0.239
#>  6 08NM116        1949-04-06 Flow       2.21 NA        0.239
#>  7 08NM116        1949-04-07 Flow       2.27 NA        0.245
#>  8 08NM116        1949-04-08 Flow       2.35 NA        0.254
#>  9 08NM116        1949-04-09 Flow       2.78 NA        0.300
#> 10 08NM116        1949-04-10 Flow       2.94 NA        0.318
#> # … with 23,069 more rows