calc_magLow: Indices describing magnitude of the low flow condition.

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

Indices describing magnitude of the low flow condition.

Description

Calculates 27 indices used to describe the magnitude of the peak flow condition. See Table X in the EflowStats package vignette for a full description of indices.

Usage

calc_magLow(
  x,
  yearType = "water",
  wyMonth = 10L,
  digits = 3,
  drainArea = NULL,
  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
drainArea	A numeric specifying the drainage area. Only required for ml22 statistic. Typically squiare miles, see details.
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.

• mh1_12 Requires pref argument to be either "mean" or "median" specifying monthly aggregation function. Default is "mean". Means (or medians - use preference option) of maximum daily flow values for each month. For example, mh1 is the mean of all January maximum flow values over the entire record.

• mh13 variability (coefficient of variation) across minimum monthly flow values. Compute the mean and standard deviation for the maximum monthly flows over the entire flow record. MH13 is the standard deviation times 100 divided by the mean maximum monthly flow for all years.

• ml14 Mean of annual minimum annual flows. ML14 is the mean of the ratios of minimum annual flows to the median flow for each year.

• ml15 Low flow index. ML15 is the mean (or median-Use Preference option) of the ratios of minimum annual flows to the mean flow for each year.

• ml16 Median of annual minimum flows. ML16 is the median of the ratios of minimum annual flows to the median flow for each year.

• ml17 Baseflow 1. Compute the mean annual flows. Compute the minimum of a 7-day moving average flow for each year and divide them by the mean annual flow for that year. ML17 is the mean (or median-Use Preference option) of those ratios.

• ml18 Variability in baseflow 1. Compute the standard deviation for the ratios of minimum 7-day moving average flows to mean annual flows for each year. ML18 is the standard deviation times 100 divided by the mean of the ratios.

• ml19 Baseflow 2. Compute the ratios of the minimum annual flow to mean annual flow for each year. ML19 is the mean (or median-Use Preference option) of these ratios times 100.

• ml20 Baseflow 3. Divide the daily flow record into 5-day blocks. Find the minimum flow for each block. Assign the minimum flow as a base flow for that block if 90 percent of that minimum flow is less than the minimum flows for the blocks on either side. Otherwise, set it to zero. Fill in the zero values using linear interpolation. Compute the total flow for the entire record and the total base flow for the entire record. ML20 is the ratio of total base flow to total flow.

• ml21 Variability across annual minimum flows. Compute the mean and standard deviation for the annual minimum flows. ML21 is the standard deviation times 100 divided by the mean.

• ml22 Specific mean annual minimum flow. ML22 is the mean (or median-Use Preference option) of the annual minimum flows divided by the drainage area.

Value

A data.frame of flow statistics

Examples

x <- sampleData[c("date","discharge")]
drainArea <- 50
yearType = "water"
calc_magLow(x=x,yearType=yearType,drainArea=drainArea)

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