calc_magHigh: Indices describing magnitude of the peak flow condition.

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

Indices describing magnitude of the peak 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_magHigh(
  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 charcter 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 mh20 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 maximum 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.

• mh14 median of annual maximum flows. Compute the annual maximum flows from monthly maximum flows. Compute the ratio of annual maximum flow to median annual flow for each year. MH14 is the median of these ratios.

• mh15_17 MH15; High flow discharge index. Compute the 1-percent exceedence value for the entire data record. MH15 is the 1-percent exceedence value divided by the median flow for the entire record. MH16; Compute the 10-percent exceedence value for the entire data record. MH16 is the 10-percent exceedence value divided by the median flow for the entire record. MH17; Compute the 25-percent exceedence value for the entire data record. MH17 is the 25-percent exceedence value divided by the median flow for the entire record.

• mh18 variability across annual maximum flows. Compute the logs (log10) of the maximum annual flows. Find the standard deviation and mean for these values. MH18 is the standard deviation times 100 divided by the mean.

• mh19 the skewness in annual maximum flows (dimensionless-spatial). Use the equation: MH19 numerator = N2 ? sum(qm3)-3N ? sum(qm) ? sum(qm2) + 2 ? (sum(qm))3 denominator = N ? (N-1) ? (N-2) ? stddev3 Where: N = Number of years qm = Log10 (annual maximum flows) stddev = Standard deviation of the annual maximum flows

• mh20 specific mean annual maximum flow. MH20 is the mean (or median-Use Preference option) of the annual maximum flows divided by the drainage area (cubic feet per second/square mile-temporal).

• mh21_27 high flow volume indices. Compute the average volume for flow events above a threshold. Thresholds are equal to the median flow for the entire record for mh21, 3 times the median flow for the entire record for mh22,and 7 times the median flow for the entire record for mh23. Thresholds are equal to the median flow for the entire record for mh24, 3 times the median flow for the entire record for mh25, 7 times the median flow for the entire record for mh26, and the 75th percentile for the entire record for mh27. MH21 through 23 are the average volumes divided by the median flow for the entire record. MH24 through 27 are the average peak flows divided by the median flow for the entire record.

Value

A data.frame of flow statistics

Examples

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

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