capzone: Calculate the capture zone of a well element

Description

capzone() determines the capture zone of a well element in the flow field by performing backward particle tracking until the requested time is reached.

Usage

capzone(aem, well, time, npar = 15, dt = time/10, zstart = aem$base, ...)

Value

capzone() returns an object of class tracelines.

Arguments

aem: aem object.
well: analytic element of class well.
time: numeric, time of the capture zone.
npar: integer, number of particles to use in the backward tracking. Defaults to 15.
dt: numeric, time step length used in the particle tracking. Defaults time / 10.
zstart: numeric value with the starting elevation of the particles. Defaults to the base of the aquifer.
...: additional arguments passed to tracelines().

Details

capzone() is a thin wrapper around tracelines(). Backward particle tracking is performed using tracelines() and setting forward = FALSE. Initial particle locations are computed by equally spacing npar locations at the well radius at the zstart elevation. To obtain a sharper delineation of the capture zone envelope, try using more particles or decreasing dt.

Note that different zstart values only have an effect in models with vertical flow components.

Examples

Run this code

# A model with vertical flow components
k <- 10
top <- 10; base <- 0
n <- 0.3

uf <- uniformflow(TR = 100, gradient = 0.001, angle = -10)
rf <- constant(TR, xc = -1000, yc = 0, hc = 20)
w1 <- well(200, 50, Q = 250)
w2 <- well(-200, -100, Q = 450)
as <- areasink(0, 0, N = 0.001, R = 1500)

m <- aem(k, top, base, n = n, uf, rf, w1, w2, as)

# 5-year capture zone at two different starting levels
# here, the number of particles are set to small values to speed up the examples
# increase the number of particles to obtain a sharper delineation of the envelope
cp5a <- capzone(m, w1, time = 5 * 365, zstart = base, npar = 6, dt = 365 / 4)
cp5b <- capzone(m, w1, time = 5 * 365, zstart = 8, npar = 6, dt = 365 / 4)

xg <- seq(-800, 800, length = 100)
yg <- seq(-500, 500, length = 100)
contours(m, xg, yg, col = 'dodgerblue', nlevels = 20)
plot(cp5a, add = TRUE)
plot(cp5b, add = TRUE, col = 'forestgreen') # smaller zone

# plot the convex hull of the endpoints as a polygon
endp <- endpoints(cp5b)
hull <- chull(endp[, c('x', 'y')])
polygon(endp[hull, c('x', 'y')], col = adjustcolor('forestgreen', alpha.f = 0.7))