lfstat-package: Calculates Low Flow Statistics for daily stream flow data

In lfstat: Calculation of Low Flow Statistics for Daily Stream Flow Data

Description

The "Manual on Low-flow Estimation and Prediction", published by the World Meteorological Organisation (WMO), gives an idea how to analyse stream flow data focusing on low-flow issues. This packages gives functions to compute the described statistics and produce plots similar to the one in the manual.

Details

### Create 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 baseflow.

"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 lfobj:

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.

### Indices

Functions available meanflow, Qxx, MAM (mean annual minima), BFI, recession (recession constant), streamdef (Streamflow deficit), tyears (Extreme value - T-years event), seasratio, seasindex and multistationsreport.

### Plots

hydrograph recessionplot (Diagnosis for recession) fdc (Flow-duration-curve) sbplot (seasonal barchart) seglenplot (select recession length for recession) streamdefplot (Streamflow deficit) rfa (Regional frequency analysis) dmcurve (Double mass curve)

Author(s)

Daniel Koffler <[e-mail]> and Gregor Laaha <[e-mail]>

References

Gustard, A. & Demuth, S. (2009) (Eds) Manual on Low-flow Estimation and Prediction. Operational Hydrology Report No. 50, WMO-No. 1029, 136p.

lfstat documentation built on May 2, 2019, 6:07 p.m.