IHA: Indicators of Hydrologic Alteration

In mkoohafkan/flowregime: Environmental Flow Regime Indicators

Description

Compute the Indicators of Hydrologic Alteration for a daily time series.

Usage

IHA(ts, yearstart = "01-01", yearend = "12-31", groups = 1:5, ut, lt,
  parametric = TRUE)

Arguments

ts	A time series of class xts.
yearstart	A character vector specifying the month and day signifying the start of the water year, in the format "mm-dd". Default is "01-01".
yearend	A character vector specifying the month and day signifying the end of the water year, in the format "mm-dd". Default is "12-31".
groups	The parameter groups to compute. Computes all groups (1-5) by default.
ut	The upper flow threshold for identifying high flow pulses. IHA recommends the 75th flow percentile for pre-impact conditions.
lt	The lower flow threshold for identifying low flow pulses. IHA recommends the 25th flow percentile for pre-impact conditions.
parametric	Logical: perform parametric (mean) or non-parametric (median) analysis.

Details

The IHA method requires a regular time series with no missing values.

Value

An IHA object containing the the parameter names, the value of the attribute and the year of record (YoR) for which the attribute was computed. Use summary() to report the central tendencies and measures of dispersion for each parameter and confint() to compute parametric or non-parametric confidence intervals for the summary statistics.

Notes

• Low- and high-flow pulses occurring at the start of a year of record are ignored when calculating number of pulses and mean duration of pulses.

• IHA v7 rounds averages of flow values to the nearest whole number for individual water years, and this rounding propagates through the scorecard. Numerical results may differ slightly from IHAv7.

References

Richter, B. D., Baumgartner, J. V., Powell, J. and Braun, D. P. (1996), A Method for Assessing Hydrologic Alteration within Ecosystems. Conservation Biology, 10: 1163-1174. doi: 10.1046/j.1523-1739.1996.10041163.x

Examples

data(siouxcity)
IHA(siouxcity['2009/2011'], ut = 32000, lt = 12000)
IHA(siouxcity['2009-10-01/2011-09-30'], yearstart = "10-01", 
  yearend = "09-30", ut = 32000, lt = 12000, parametric = FALSE)

mkoohafkan/flowregime documentation built on May 23, 2019, 2:02 a.m.