Drainage Coefficient (mm/day or in/day):  Defines the rate of water removed from a field over a period of time. It varies by design and by purpose. Most conventional drainage systems use a 3/8 drainage coefficient. Interceptor systems often use a 1/2 drainage coefficient. Contour systems, especially subirrigation systems that have closer tile lateral spacing, are upwards of a 3/4 drainage coefficient. Some specialty crops have even higher.

Drain Spacing (m or ft):  Defines how far apart the the pipe is for determining the catchment area of each pipe.