Numerical solutions of Richards' equation were used to compare the ste
ady state rainfall ease to the falling water table ease of water flow
to shallow drains in a uniform sand profile and in a layered silt loam
soil. Equipotentials, streamlines, and velocity distributions were ca
lculated. For saturated flow the velocity near the drain was 200 to 25
0 times the velocity near the midpoint between drains, and the drain o
utflow rate was less than 10% of the saturated hydraulic conductivity
of the soil profile. For a given drain flow rate the steady rainfall c
ase always showed greater flow from areas further removed from the dra
in than did the falling water table ease. Flow in the capillary fringe
above the water table was generally more horizontal for the falling w
ater table case than for the steady rainfall case. Flow in the zone ab
ove the capillary fringe tended to be more vertical. With shallow drai
ns, and especially in clay and silty clay soils, the capillary fringe
may extend to near the soil surface so that most of the flow above the
water table may have a significant horizontal component.