R: Exponential store with zero flows and thresholded loss

leakyExpStore.sim {hydromad}

R Documentation

Exponential store with zero flows and thresholded loss

Description

An exponential store (linear transfer function) which has a loss term, produces no flow when the store drops below a level, and can therefore model longer-term disconnection of a store from streamflow.

Usage

leakyExpStore.sim(x, tau, loss, thres, init = 0,
  return_components = FALSE)

Arguments

`x`	input time series.
`tau`	Time constant for flow from exponential store.
`loss`	Constant loss that occurs while the value of the store is greater than `thres`. See details.
`thres`	Trigger level to turn off loss, which can be interpreted as a store capacity.
`init`	Initial value of exponential store
`return_components`	whether to return store value (G) as well as flow (Q)

Details

Storage is increased by effective rainfall and decreased by flow and losses.

G[k] = G[k-1] + U[k] - Q[k] - L[k]

Flow is proportional to storage

Q[k] = a G[k], G[k]>0

Q[k] = 0, otherwise

Loss switches off at some threshold, as a piece-wise continuous function.

L[k] = L, G[k]>T+L (with T<=0)

L[k] = G[k] - T, T+L > G[k] > T

L[k] = 0, G[k]<T

Value

the flow time series with the same dimensions and time windows as the input x. If return_components = TRUE, it will have multiple columns named G and Q.

Author(s)

Joseph Guillaume joseph.guillaume@anu.edu.au with advice from Barry Croke

Examples

U  <- ts(c(1, rep(0, 10),1,rep(0, 20)))

## Without a loss, equivalent to expuh
##  Loss threshold has no effect
all.equal(leakyExpStore.sim(U,5,loss=0,thres=0),expuh.sim(U, tau_s = 5))

## With losses stopping when flow stops, equivalent to expuh with a loss
all.equal(leakyExpStore.sim(U,5,loss=0.1,thres=0),
  expuh.sim(U, tau_s = 5,loss=0.1))

## Plot of unit hydrographs
xyplot(cbind("U"=U,
"loss=0"=expuh.sim(U,tau_s=5),
"loss=0.1 & thres=0"=expuh.sim(U,tau_s=5,loss=0.1),
"loss=0.1 & thres=-0.3"=leakyExpStore.sim(U,5,loss=0.1,thres=-0.3),
"loss=0.1 & thres=-Inf"=leakyExpStore.sim(U,5,loss=0.1,thres=-Inf)
),superpose=TRUE)

## Time series plot of value of store
xyplot(cbind(
"thres=0"=leakyExpStore.sim(U,5,loss=0.1,thres=0,
  return_components=TRUE)[,"G"],
"thres=-0.3"=leakyExpStore.sim(U,5,loss=0.1,thres=-0.3,
  return_components=TRUE)[,"G"],
"thres=-Inf"=leakyExpStore.sim(U,5,loss=0.1,thres=-Inf,
  return_components=TRUE)[,"G"]
),superpose=TRUE)

## Time series of loss
xyplot(cbind(
"thres=0"=leakyExpStore.sim(U,5,loss=0.1,thres=0,
  return_components=TRUE)[,"L"],
"thres=-0.3"=leakyExpStore.sim(U,5,loss=0.1,thres=-0.3,
  return_components=TRUE)[,"L"],
"thres=-Inf"=leakyExpStore.sim(U,5,loss=0.1,thres=-Inf,
  return_components=TRUE)[,"L"]
),superpose=TRUE)

[Package hydromad version 0.9-18 Index]