FLOWTHRU is an interactive program which requires the user to provide a number of simple parameters to define the problem of interest.

You need to provide data of three types: aquifer geometry, boundary fluxes and hydraulic conductivity, and display options.

Aquifer geometry

First, it is usual to define the geometry of the vertical section of interest. You need to define the thickness of the aquifer, B, and the ratio of the length of the water body to aquifer thickness, 2a/B.

If the water body has a low conductivity sediment lining at its base, you can also define the effective thickness D of the lining as a ratio D/B.

The default parameters are B=50 m and 2a/B=1, i.e. a water body 50 m long in the direction of aquifer flow, in an aquifer 50 m thick.

B =		[L]
2a/B =	0.25 0.5 1 2 4 8 16 32 64 128 256
D/B =	0.0 0.01 0.02 0.05 0.1 0.2 0.5 1 2 5 10

The value of L, which defines the distance between the water body and the upgradient and downgradient boundaries cannot be selected by the user and is set equal to the product of 2B and the square root of the anisotropy ratio, K_x/K_z.

Boundary fluxes and hydraulic conductivity

Please choose values for the following parameters in a consistent set of units, such as metres and days. Fluxes have dimensions of length per unit time, because they are really volumes per unit time, per unit depth of aquifer, per unit thickness of vertical section. FLOWTHRU allows you to choose a horizontal conductivity and an anisotropy ratio from a restricted range.

All three fluxes can be positive or negative, with the positive direction defined in the figure below. The default values are U₊=0.01 m/d, U_-=0.01 m/d, R=0.001 m/d and K_x=1 m/d, with K_x/K_z=1 (an isotropic aquifer).

U+ =		[L/T]
U- =		[L/T]
R =		[L/T]
Kx =		[L/T]
Kx/Kz =	1 4 16 64 256 1024

The value of Q, the net inflow from the water body to the aquifer, is determined by your choices of aquifer inflow, aquifer outflow and recharge to the water table. It is not an independent variable.

Display options

You can select the types of output you wish to see. The key to understanding surface water - groundwater interaction is the location of dividing streamlines!

You can either plot the flow pattern, using the flow options above, or plot the seepage distribution, which shows an enhanced distribution of fluxes through the bed of the water body.