13.1.1 Aquifers

Aquifers may be confined or unconfined. For confined parts, you must input the elastic storativity c_e as a constant, DIANA derives the horizontal transmissivity T in confined aquifers from the saturated conductivity k_s , using

T_confined = (x_top.Z - x_bottom.Z)k_s (13.1)

with x_Z the location component in Z direction. DIANA derives the capacitance c per unit of area from the elastic storativity, using

c = (x_top.Z - x_bottom.Z)c_e (13.2)

Diana offers special aquifer elements to model aquifers with unconfined parts [Vol. Element Library]. In unconfined aquifers, DIANA takes the phreatic storativity c_p equal to the porosity n , and derives the horizontal transmissivity from

$$\left(\vphantom{ ( \phi - x_{\mathrm{bottom}.Z} ), 0 }\right. \phi \left.\vphantom{ ( \phi - x_{\mathrm{bottom}.Z} ), 0 }\right)$$ (13.3)

Unconfined aquifers require a nonlinear analysis.

    (syntax)

CONDUC

k is the (isotropic) saturated conductivity k_s , typically in m/s . For orthotropic and anisotropic material, the values kxx, and kyy are the conductivities k_s.xx , and k_s.yy in the local element xy directions which may be user-specified. For anisotropic material, the value kxy is the conductivity k_s.xy .

Note that the number of specified k values indicates the type of conductivity: one value is isotropic, two values is orthotropic and three values is anisotropic.

STORAT

c is the elastic storativity c_e of confined aquifers.

POROSI

n is the value of the effective porosity n , which equals the phreatic storativity c_p of unconfined aquifers. ( 0 $\leq$ n $\leq$ 1 )

    (file.dat)

'MATERI'
    1 CONDUC  0.01
    2 CONDUC  0.01 0.015
    3 CONDUC  0.01 0.015 0.007

This example input specifies isotropic conductivity for material 1 with k_s = 0.01 . The conductivity of material 2 is orthotropic with k_s.xx = 0.01 and k_s.yy = 0.015 . For material 3, the conductivity is anisotropic with k_s.xx = 0.01 , k_s.yy = 0.015 and k_s.xy = 0.007 .