114 C.W.W.NG AND Q.SHI an3=anisotropic Table 4.1 Input parameters based on a 10-year return period (1980–1990). an1, an1, du5=durations; du4, du3, du2, du1, permeability ratios; k1, k2, k3=water permeabilities. i3=intensities; Notes i2, i1,