mqt {FlowScreen}

Moving quantile threshold

Description

This function calculates the daily moving window quantile threshold for use in identifying the partial duration series of streamflow droughts.

Usage

mqt(TS, Qdr = 0.2, WinSize = 30)

Arguments

TS

output from create.ts containing a data.frame of flow time series

Qdr

Numeric value of the drought threshold quantile. Default is 0.2.

WinSize

Numeric value specifying the size of the moving window in days. Default is 30.

Details

The threshold is defined by a moving quantile, where daily threshold values are based on the 80th percentile of the flow duration curve (i.e. 0.2 quantile) from a 30-day moving window (Beyene et al. 2014). With this method, every day of the year has a different threshold based on the streamflow measured on the day, the 15 days before the day, and the 15 days after the day.The size of the moving window can be modified with the WinSize argument, and the percentile can be modified with the Qdr argument.

Value

Returns a numeric vector containing the streamflow drought threshold in m3/s for each day of the year.

Author(s)

Jennifer Dierauer

References

Beyene, B.S., Van Loon, A.F., Van Lanen, H.A.J., Torfs, P.J.J.F., 2014. Investigation of variable threshold level approaches for hydrological drought identification. Hydrol. Earth Syst. Sci. Discuss. 11, 12765-12797. http://dx.doi.org/10.5194/hessd-11-12765-2014.

See Also

See create.ts to format the input flow series.

The following functions use this function: dr.pds, dr.events, dr.seas

Examples

data(cania.sub.ts)
res <- mqt(cania.sub.ts)

# subset one year of the flow series
flow.sub <- cania.sub.ts[cania.sub.ts$year == 1990,]

# plot the 1990 observed flows in dark blue and the daily drought threshold in red
plot(flow.sub$doy, flow.sub$Flow, ylab="Q (m3/s)", xlab="Day of Year",
 pch=19, col="darkblue", type="b")
points(res, pch=19, cex=0.7, col="red")