...
D depth points, corners of grid cells
Z water level points, cell centres of grid , http://en.wikipedia.org/wiki/Face_(geometry)
UV velocity points, contravariant
Length of dimensions
D = 2xZ + 2
Z = n Cells
UV = 3xZ + 1 i number of rows
j number of columns
D = (i+1) * (j+1)
Z = i * j
U = (i+1)j
V = i(j+1)