Agriculture and Agribusiness

Land Drainage and Salinity Control

Irrigated land in dry climates accumulates salt because every irrigation brings salt in and only drainage takes it out, so a scheme without drainage is on a schedule to fail that can run for decades before it becomes obvious. This course covers preventing that. Delegates work through the salt balance and why leaching alone does not solve the problem if the water table rises. Water table behaviour and capillary rise are addressed, including the depth at which salt concentrates in the root zone. Drainage investigation follows, covering piezometers, water table mapping and the hydraulic conductivity testing a design depends on. Subsurface drainage design is covered through drain spacing, depth, pipe sizing, envelope material and the steady state and transient approaches. Surface drainage and field layout follow. Drainage water disposal is treated as the difficulty it is, since drainage water is saline and its discharge is regulated. Reclamation of salt affected soils is covered, including gypsum use for sodic soils. The course closes on monitoring and on maintaining a drainage system nobody can see.