2.2. Effective Specific Storage

The effective specific storage \(S_s'\) reflects the elasticity of water and the porous medium matrix \(S_s\). At the phreatic surface, it reflects the specific yield (\(S_y\)) from phreatic surface movement. In MINEDW, the effective specific storage is defined as:

(2.7)\[S_s' = S_s + \frac{S_y \cdot A}{V}\]

Where:

• \(S_s'\) = effective specific storage [L⁻¹],

• \(S_s\) = specific storage [L⁻¹],

• \(S_y\) = specific yield at the phreatic surface [L⁰],

• \(V\) = specified volume of medium [L³], and

• \(A\) = area of the phreatic surface within the specified volume [L²].

MINEDW solves these equations using the Galerkin finite-element approximation described by Durbin and Berenbrock (1985) [1]. The groundwater solution iterates based on user-specified closure criteria, solver options, and maximum allowed iterations. User-defined values vary with the groundwater flow model and application. Define closure criteria to minimize water budget residuals in transient simulations or storage changes in steady-state simulations.