baseflow {lfstat}

Calculate the base flow of a river

Description

Given a stream flow hydrograph of flows (regular time series), the base flow is separated. The minima of a period (default block.len = 5) is calculated and turning points are identified. At turning points the base flow equals the actual flow, in between, linear interpolation is carried out.

Usage

baseflow(x, tp.factor = 0.9, block.len = 5)

Arguments

x

numeric vector containing flows

tp.factor

numeric vector of length one. Towards high flows, allow the central value of three consecutive minima only to be of a factor (1 - tp.factor) higher than the surrounding values

block.len

numeric vector of length one.

Value

A numeric vector of length(x). It contains NAs as until the first turning point, the base flow cannot be determined.

References

Tallaksen, L. M. and Van Lanen, H. A. J. 2004 Hydrological Drought: Processes and Estimation Methods for Streamflow and Groundwater. Developments in Water Science 48, Amsterdam: Elsevier.

Examples

## reproducing Tallaksen and van Lanen (2004)
## Example 5.3 Base Flow Index"

data(ray)
ray <- as.xts(ray)

# calculate base flow and plot it
ray$baseflow <- baseflow(ray$discharge)
ray96 <- ray[format(time(ray), "%Y") == "1996", ]
plot(ray96$discharge, type = "l")
lines(ray96$baseflow, col = 2)

# aggregated base flows for river Ray
# these are mean flow totals per day, not per year as written
# in Tallaksen and van Lanen (2004)
round(colSums(ray96[, c("discharge", "baseflow")]), 2)