(1) In a water balance: sum of water lost from a given land area during any specific time by transpiration from vegetation (agricultural crops or native vegetation) and building of plant tissue, by evaporation from water surfaces, soil moisture and snow, and by interception. (2) In irrigation: the losses made up of seepage and evaporation from canals and ditches, water wasted from the canal system, excess water drained from land surfaces, and water lost from the soil by deep percolation below the root zone. (GHP)
