Computes the annual flow duration curve of a river discharge data set.

Usage

computeAnnualFlowDurationCurve(data, column, date = "Date")

Arguments

data: Tibble with date and discharge in columns.
column: Name of the column with data to calculate duration curve from.
date: Name of the date column

Value

Input tibble with sorted data and duration stats in columns, namely

Q: Discharge in descending order

Ma: A day counter between 1 and 365/366

Pa: Exceedance probability in percent

Note

If the input data tibble is grouped, the duration stats will be computed within each group.

Examples

# Monthly flow duration curve
Qdf <- tibble::tibble(
  Date = seq.Date(from = lubridate::as_date("2020-01-01"),
                  to = lubridate::as_date("2022-12-13"),
                  by = "month"),
  Q = rep(c(1:6, 6:1), 3)
)
DurationCurve <- computeAnnualFlowDurationCurve(Qdf, "Q", "Date")
plot(DurationCurve$Ma, DurationCurve$Q)


# Daily flow duration curve
Date = seq.Date(from = lubridate::as_date("2019-10-01"),
                to = lubridate::as_date("2040-09-30"), by = "day")
Qdfdaily <- tibble::tibble(Date = Date,
  Q = sin(2*pi/365*c(1:length(Date))) * stats::runif(length(Date)) +
    cos(2*pi/365*c(1:length(Date))) * runif(length(Date)) +
    runif(length(Date))*2)
DurationCurve <- computeAnnualFlowDurationCurve(Qdfdaily, "Q", "Date")