Controlled drainage systems use ditches and other structures to control and divert water from sloughs. Diversion is the least complicated of spring backflood irrigation systems. A dike across a natural water run holds water on the land until the water has served its purpose. Pumped diversion systems use water from creeks or rivers to irrigate fields. Pumped drainage systems are used in areas where the topography does not allow for adequate natural drainage.
Water is pumped off from a sump at the lowest end of the field and into a natural watercourse.
The object is to fill the root zone and then use the stored water during the growing season. Cropping the soil dry each season prevents the buildup of subsoil water levels and ensures the soil will be dry enough to absorb water the following spring. If the subsoil gets oversaturated, the only way it can dry is by evaporation, which brings softs to the surface. Oversaturating also cuts down on yields because it causes shallow rooting and plants suffer during hot, dry weather. A probe can be used to measure the moisture depth.