calc_durationLow: Indices describing duration of low flow events.

In USGS-R/EflowStats: Hydrologic Indicator and Alteration Stats

Indices describing duration of low flow events.

Description

Calculates 24 indices used to describe the duration of low flow conditions. See Table X in the EflowStats package vignette for a full description of indices.

Usage

calc_durationLow(
  x,
  yearType = "water",
  wyMonth = 10L,
  digits = 3,
  pref = "mean",
  ...
)

Arguments

x	A dataframe containing a vector of date values in the first column and vector of numeric flow values in the second column.
yearType	A character of either "water" or "calendar" indicating whether to use water years or calendar years, respectively.
wyMonth	A numeric. The month of the year in which the water year starts (1=January, 12=December). The water year begins on the first day of wyMonth.
digits	A numeric. Number of digits to round indice values
pref	A character of either "mean" or "median", indicating whether to use mean or median. See details.
...	Optional arguments needed for calc_allHIT function

Details

Descriptions of indices.

• dl1 Annual minimum daily flow. Compute the minimum 1-day average flow for each year. DL1 is the mean (or median-Use Preference option) of these values.

• dl2 Annual minimum of 3-day moving average flow. Compute the minimum of a 3-day moving average flow for each year. DL2 is the mean (or median-Use Preference option) of these values.

• dl3 Annual minimum of 7-day moving average flows. Compute the minimum of a 7-day moving average flow for each year. DL3 is the mean (or median-Use Preference option) of these values.

• dl4 Annual minimum of 30-day moving average flows. Compute the minimum of a 30-day moving average flow for each year. DH4 is the mean (or median-Use Preference option) of these values.

• dl5 Annual minimum of 90-day moving average flows. Compute the minimum of a 90-day moving average flow for each year. DH5 is the mean (or median-Use Preference option) of these values.

• dl6 Variability of annual minimum daily average flow. Compute the standard deviation for the minimum daily average flow. DL6 is 100 times the standard deviation divided by the mean.

• dl7 Variability of annual minimum of 3-day moving average flows. Compute the standard deviation for the minimum 3-day moving averages. DL7 is 100 times the standard deviation divided by the mean.

• dl8 Variability of annual minimum of 7-day moving average flows. Compute the standard deviation for the minimum 7-day moving averages. DL8 is 100 times the standard deviation divided by the mean.

• dl9 Variability of annual minimum of 30-day moving average flows. Compute the standard deviation for the minimum 30-day moving averages. DL9 is 100 times the standard deviation divided by the mean.

• dl10 Variability of annual minimum of 90-day moving average flows. Compute the standard deviation for the minimum 90-day moving averages. DH10 is 100 times the standard deviation divided by the mean.

• dl11 Annual minimum daily flow divided by the median for the entire record. Compute the minimum daily flow for each year. DL11 is the mean of these values divided by the median for the entire record.

• dl12 Annual minimum of 7-day moving average flows divided by the median for the entire record. Compute the minimum of a 7-day moving average flow for each year. DL12 is the mean of these values divided by the median for the entire record.

• dl13 Annual minimum of 30-day moving average flows divided by the median for the entire record. Compute the minimum of a 30-day moving average flow for each year. DL13 is the mean of these values divided by the median for the entire record.

• dl14 Low exceedence flows. Compute the 75-percent exceedence value for the entire flow record. DL14 is the exceedence value divided by the median for the entire record.

• dl15 Low exceedence flows. Compute the 90-percent exceedence value for the entire flow record. DL15 is the exceedence value divided by the median for the entire record.

• dl16 Low flow pulse duration. Compute the average pulse duration for each year for flow events below a threshold equal to the 25th percentile value for the entire flow record. DL16 is the median of the yearly average durations.

• dl17 Variability in low pulse duration. Compute the standard deviation for the yearly average low pulse durations. DL17 is 100 times the standard deviation divided by the mean of the yearly average low pulse durations.

• dl18 Number of zero-flow days. Count the number of zero-flow days for the entire flow record. DL18 is the mean (or median-Use Preference option) annual number of zero flow days.

• dl19 Variability in the number of zero-flow days. Compute the standard deviation for the annual number of zero-flow days. DL19 is 100 times the standard deviation divided by the mean annual number of zero-flow days.

• dl20 Number of zero-flow months. While computing the mean monthly flow values, count the number of months in which there was no flow over the entire flow record.

Value

A data.frame of flow statistics

Examples

x <- sampleData[c("date","discharge")]
yearType = "water"
calc_durationLow(x=x,yearType=yearType)

USGS-R/EflowStats documentation built on Sept. 30, 2023, 9:31 p.m.