Basin‐Wide Impacts of Irrigation Efficiency

Irrigation efficiency is one of the important factors affecting river basin water quality. Questions frequently arise as to whether increasing irrigation efficiency in a basin will have a net positive or a net negative effect on basin water quality. Quality and quantity of return flow from irrigation are related to irrigation efficiencies and leaching fractions. River basins have leaching fractions analogous to irrigation leaching fractions inasmuch as salts generated by mineral weathering and those dissolved by percolating waters are carried out of the basin by a fraction of the precipitation falling on the basin. Reducing the leaching fraction of a basin by increasing irrigation efficiency and consuming more water in the basin will decrease downstream water quality and quantity. Irrigation efficiency, as a salinity control measure, must be considered in the context of total water management to be properly interpreted.