ABSTRACT
Most irrigation is on fragile arid soils that have enormous crop yield potential when irrigated. However, the yield potential is easily lost if the thin veneer of topsoil is eroded. Runoff and irrigation return flows (necessary in many surface irrigation schemes) deliver sediment (human, animal and plant pathogens; nutrients and pesticides) to downstream fields and riparian waters. These pollutants accumulate in runoff primarily as a result of erosion.
