gr_baseflow {grwat}

Extract baseflow

Description

Extract baseflow from hydrological series using the filtering approach

Usage

gr_baseflow(
  Q,
  a = 0.925,
  k = 0.975,
  C = 0.05,
  aq = -0.5,
  passes = 3,
  padding = 30,
  method = "lynehollick"
)

Arguments

Q

Numeric runoff vector.

a

Numeric value of a filtering parameter used in 'chapman', 'jakeman' and 'lynehollick' methods. Defaults to 0.925.

k

Numeric value of a filtering parameter used in 'boughton' and 'maxwell' methods. Defaults to 0.975.

C

Numeric value of a separation shape parameter used in 'boughton', 'jakeman' and 'maxwell' methods

aq

Numeric value of a filtering parameter used in 'jakeman' method. Defaults to -0.5.

passes

Integer number of filtering iterations. The first iteration is forward, second is backward, third is forward and so on. Defaults to 3.

padding

Integer number of elements padded at the beginning and ending of runoff vector to reduce boundary effects. Defaults to 30.

method

Character string to set baseflow filtering method. Available methods are 'boughton', 'chapman', 'furey', 'jakeman', 'lynehollick' and 'maxwell'. Default is 'lynehollick', which corresponds to Lyne-Hollick (1979) hydrograph separation method.

Value

Numeric baseflow vector with length equal to Q

Examples

library(grwat)
library(ggplot2)
library(dplyr)
library(tidyr)
library(lubridate)

data(spas) # example Spas-Zagorye data is included with grwat package

# Calculate baseflow using Line-Hollick approach
hdata = spas %>% 
  mutate(Qbase = gr_baseflow(Q, method = 'lynehollick', 
                             a = 0.925, passes = 3))

# Visualize for 1980 year
ggplot(hdata) +
  geom_area(aes(Date, Q), fill = 'steelblue', color = 'black') +
  geom_area(aes(Date, Qbase), fill = 'orangered', color = 'black') +
  scale_x_date(limits = c(ymd(19800101), ymd(19801231)))

# Compare various approaches
hdata = spas %>%
  mutate(lynehollick = gr_baseflow(Q, method = 'lynehollick', a = 0.9),
         boughton = gr_baseflow(Q, method = 'boughton', k = 0.9),
         jakeman = gr_baseflow(Q, method = 'jakeman', k = 0.9),
         maxwell = gr_baseflow(Q, method = 'maxwell', k = 0.9)) %>% 
  pivot_longer(lynehollick:maxwell, names_to = 'Method', values_to = 'Qbase')

# Visualize for 1980 year
ggplot(hdata) +
  geom_area(aes(Date, Q), fill = 'steelblue', color = 'black') +
  geom_area(aes(Date, Qbase), fill = 'orangered', color = 'black') +
  scale_x_date(limits = c(ymd(19810101), ymd(19811231))) +
  facet_wrap(~Method)

# Compare Lyne to Kudelin
p = gr_get_params('center')
p$filter = 'kudelin'

hdata = spas %>% 
  mutate(lynehollick = gr_baseflow(Q, method = 'lynehollick', 
                                   a = 0.925, passes = 3),
         kudelin = gr_separate(spas, p)$Qbase) %>% 
  pivot_longer(lynehollick:kudelin, names_to = 'Method', values_to = 'Qbase')

# Visualize for 1980 year
ggplot(hdata) +
  geom_area(aes(Date, Q), fill = 'steelblue', color = 'black') +
  geom_area(aes(Date, Qbase), fill = 'orangered', color = 'black') +
  scale_x_date(limits = c(ymd(19800101), ymd(19801231))) +
  facet_wrap(~Method)