Flow Duration Curve (FDC) signature

Computes FDCsign, an aggregated index combining four percent-bias metrics for distinct flow regimes (peak, high, intermediate, and low), summarizing model performance across the flow regime spectrum. See Details for its calculation and component definitions.

Usage

fdc_signature(sim, obs)

Arguments

sim

numeric. Simulated flow values.

obs

numeric. Observed flow values.

Value

A tibble with five columns: Speak, Shigh, Smid, Slow (all expressed as percent bias), and FDCsign (aggregated index, unitless).

Details

The index FDCsign is computed as: $$ FDCsign = 0.25 \times \big( |Speak/100| + |Shigh/100| + |Smid/100| + |Slow/100| \big) $$ where each component is defined as:

• Speak: Percent bias in the FDC peak segment volume (EP: 0–2%), computed with pbias_fdc_target_segment.

• Shigh: Percent bias in the FDC high segment volume (EP: 2–20%), computed with pbias_fdc_target_segment.

• Smid: Percent bias in the FDC midsegment slope (EP: 20–70%), computed with pbias_fdc_midsegment.

• Slow: Percent bias in the FDC low segment volume (EP: 70–100%), computed with pbias_fdc_target_segment.

See also

Other Performance evaluation: evaluate_swat(), gof_metrics(), pbias_fdc_midsegment(), pbias_fdc_target_segment(), plot_fdc(), plot_mean_annual_cycle(), plot_timeseries()

Examples

# Synthetic daily flow data
set.seed(123)
obs <- abs(rnorm(730, mean = 50, sd = 20))
sim <- obs * runif(730, min = 0.8, max = 1.5)

# Compute FDC signature
fdc_signature(sim, obs)