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Compute Runoff Coefficient

compute_Rc.Rd

Calculates the runoff coefficient (Rc) as the ratio of total streamflow volume to total precipitation volume over a specified period, typically a hydrological year.

Usage

compute_Rc(Q, R, na.rm = TRUE)

Arguments

Q

Numeric vector of streamflow/discharge values L³/T

R

Numeric vector of precipitation values L/T

na.rm

Logical indicating whether to ignore missing values (NA) in calculations. Default is TRUE.

Value

A numeric value representing the runoff coefficient (dimensionless):

  • 0 indicates no runoff

  • 1 indicates all precipitation becomes runoff

  • Values >1 suggest groundwater contributions or measurement errors

Details

The runoff coefficient is calculated as: $$Rc = \frac{\sum Q}{\sum R}$$

Important notes:

  • Input vectors must cover the same time period

  • Should be computed for complete hydrological years

  • No unit conversion is performed - ensure consistent units

  • Negative values will produce invalid results

Examples

# Example for a hydrological year
Q <- c(10, 12, 15, 20, 18, 16, 14, 12, 10, 9, 8, 7)  # Streamflow (mm/month)
P <- c(20, 25, 30, 35, 40, 45, 40, 35, 30, 25, 20, 15) # Precipitation (mm/month)

rc <- compute_Rc(Q, P)
print(paste("Runoff coefficient:", round(rc, 3)))
#> [1] "Runoff coefficient: 0.419"