lfstat-package {lfstat}

Calculation of Low Flow Statistics for Daily Stream Flow Data

Description

The "Manual on Low-flow Estimation and Prediction" (Gustard & Demuth (2009, ISBN:978-92-63-11029-9)), published by the World Meteorological Organisation, gives a comprehensive summary on how to analyse stream flow data focusing on low-flows. This packages provides functions to compute the described statistics and produces plots similar to the ones in the manual.

Details

Create an object of class lfobj (Low-Flow-Objects)

The package calculates indices and makes graphics for low flow analysis. It brings its own class 'lfobj', a special data.frame format with columns 'day', 'month', 'year', 'flow', 'hyear' and possibly 'baseflow'.

'day', 'month' and 'year' refer to the date, 'flow' is the measured runoff (unit-independent), 'baseflow' the calculated base flow.

'hyear' refers to the hydrological year. When creating the 'lfobj' you define the month where the stations hydrological year starts. If annual indices are calculated or single years are plotted, the 'hyear' is taken.

Basically there are to options to create an low flow object:

If you have special data format, e.g. GRDC, you can use the function readlfdata, see ?readlfdata to see which formats are currently supported. Otherwise you can use createlfobj. You can apply it for new data in one of two ways: 1) You create a data.frame with columns: 'day', 'month', 'year' and 'flow'. 2) You create a time-series ('ts') from 'flow' and give the start date of the series when calling 'createlfobj'.

Preparation

lfstat does not need to know the unit of the flow, but you might want it to appear in your plots. You can use setlfunit to define how units are labelled in your graphics. Examples are given in '?setlfunit'.

Please check for NA-values using lfnacheck, indices and plots are made as if series were complete. See the manual on how to deal with missing values and, if reasonable, use lfnainterpolate.

Available Indices

• meanflow

• Qxx

• MAM (mean annual minima)

• BFI

• recession (recession constant)

• streamdef (Streamflow deficit)

• tyears (Extreme value - T-years event)

• seasratio

• seasindex

• multistationsreport

Plots

• hydrograph

• recessionplot (Diagnosis for recession)

• fdc (Flow-duration-curve)

• sbplot (seasonal bar chart)

• seglenplot (select recession length for recession)

• streamdefplot (Streamflow deficit)

• rfa (Regional frequency analysis)

• dmcurve (Double mass curve)

Index of help topics:

BFI                     Base Flow Index
MAM                     Mean Annual Minimum
Qxx                     Qxx, Q95, Q90, Q70
apply.seasonal          Apply an aggregation function seasonally.
as.lfobj                Coerce to class "lfobj"
as.xts.lfobj            Convert Object To Class "xts"
baseflow                Calculate the base flow of a river
bfplot                  Base Flow Plot
check_distribution      Checks if a Distribution is suited
createlfobj             Create an low flow object for further Low Flow
                        Analysis
dmcurve                 Double Mass Curve
ev_return_period        Estimate the return period for given quantiles
evfit                   Fit an extreme value distribution to
                        observations
evquantile              Estimating populations quantiles of extreme
                        values
fdc                     Flow Duration Curve
fill_na                 Interpolation NA values in a vector
find_droughts           Identifying Low Flow Periods
flowunit                Set and retrieve unit of the discharge
gringorten              Gringorten Plotting Positions
hydrograph              Hydrograph
hyear_start             Extract or guess the Start of a Hydrological
                        Year
lfnacheck               Low flow object check for missing values.
lfnainterpolate         Interpolate missing values
lfstat-package          Calculation of Low Flow Statistics for Daily
                        Stream Flow Data
ma                      Simple Moving Average
meanflow                Mean flow
multistationsreport     Report for several stations
ngaruroro               Daily stream flow data used for low flow
                        analysis
plot.deficit            Plot time series of deficits
pooling                 Pooling Procedures of Low Flow Events
readlfdata              Reads data sheets
recession               Recession Constant
recessionplot           Recession diagnostic plot
reversing               Reversed functions for several Extreme Value
                        Distributions
rfa                     Regional Frequency Analysis
rfaplot                 Regional Frequency Analysis
rpline                  Highlight quantiles/return periods
sbplot                  Seasonal Bar Chart
seasindex               Seasonality Index
season                  Attribute dates to seasons
seasratio               Seasonality Ratio
seglenplot              Bar chart of recession length
setlfunit               Define the unit to use in low flow plots
streamdef               Streamflow Deficit
streamdefplot           Streamflow Deficit Plot
summary.deficit         Object Summaries
trace_value             Draw Paths to Points perpendicular to
                        Coordinate Axis
tyears                  Calculate Low-Flow Quantiles for given Return
                        Periods
tyearsS                 Calculate Low-Flow Quantiles for given Return
                        Periods
vary_threshold          Create varying thresholds
water_year              Compute the water year

Author(s)

NA

Maintainer: NA

References

Gustard, A. & Demuth, S. (2009) (Eds) Manual on Low-flow Estimation and Prediction. Operational Hydrology Report No. 50, WNO-No. 1029, 136p. https://library.wmo.int/doc_num.php?explnum_id=7699