1. Implicit Approximation

2. Implicit approximation can be solved using: Point iteration (G/S, SOR) Direct (matrix) solution Combination of matrix soln and iteration

3. Examples of solution techniques that combine matrix solution with iteration: IADI (see chapter 5 of W&A) SSOR* SIP* PCG2* *Used in MODFLOW

5. General 3D equation used in MODFLOW i-1 i i+1 Block centered grid xixi  x i-1/2  x i+1/2

6. K values in the space between nodes is calculated using the harmonic mean

7. The default boundary condition is no flow.

8. Types of Layers (LAYCON array) Confined Unconfined Convertible (Useful to think in terms of a layer transmissivity.)

9. Conductance