Drainage of Agricultural Lands - Practices of Irrigation and On-farm Water Management - page 358

Drain
spacing

Feeder
drain

To disposal
ditch

Fig. 9.15 Schematic of a typical layout of subsurface drainage system

9.6.4 Principles, Steps, and Considerations in Subsurface
Drainage Design

9.6.4.1 Principles

The design of a subsurface drainage system requires developing criteria that

• specify the operation of the system and the physical configuration that fulfill the

drainage objective(s).

• consider irrigation and drainage systems as an integrated water management

system.

• minimize deep percolation losses through improved irrigation water management

(source control)

• characterized by establishing the water-table depth at the mid-point between lat-

erals and the drainage coefficient (that specifies the maximum volume, expressed
as depth of water to be removed in a 24-h period)

• Specify option regarding reuse of drainage water for irrigation or stimulation of

in situ use by crop through control of water table.

In arid areas an additional design criterion is the control of salt accumulation by
capillary rise into the crop root zone, which is accomplished by managing the mid-
point water-table depth to minimize upward flow of water and salt from the shallow
ground water.

9.6.4.2 Steps

In designing subsurface drainage system in a command area or watershed, the
following steps and procedures need to be followed: