ABSTRACT
Artificial (surface and subsurface) drainage systems are designed for the timely removal of excess water from land to reduce the risk of water damage to crops, soils, or structures. The term drainage coefficient represents the quantity or rate at which water is removed by the drainage system to either lower a water table (saturated portion of the soil profile) or accommodate surface runoff. For subsurface drainage systems, drainage coefficients are usually expressed as a depth of water removed per 24 hr over the drained area (mm/day), and for surface drainage systems, as a rate of flow per unit area drained. Drainage practitioners-farmers, contractors, engineers-routinely use the term drainage coefficient as an important criterion in design, operation, and management of drainage systems.
