Figure 2. The outlet is raised after planting to potentially store water for crops.

Drainage water management is a new strategy that reduces the nitrate and phosphorus loads while maintaining adequate drainage for crop production. The following six paragraphs with slight revisions and illustrations are taken directly from a fact sheet entitled “Drainage Water Management for the Midwest WQ-44”.

Drainage water management is the practice of using a water control structure in a main, sub-main, or lateral drain to vary the depth of the drainage outlet. The water table must rise above the outlet depth for drainage to occur. The outlet depth, as determined by the control structure, is:

• Raised after harvest to limit drainage outflow and reduce the delivery of nitrate to ditches and streams during the off-season. The outlet is lowered in early spring and again in the fall so the drain can flow freely before field operations such as planting or harvest. (Figure 1)