Water control structures in subsurface (tile) drainage can help manage water in subsurface-drained fields to protect water quality and benefit your bottom line. The practice of managing the water in the field by changing the outlet elevation of the drainage system is known as controlled drainage (a.k.a. drainage water management). In this practice, water is held back in the field to allow water to travel through longer pathways through the natural filter of the soil. Managing the water level at the system outlet can help keep nutrients from leaving the field and provide valuable water for crops during the growing season.
Controlled drainage works best on fields when laterals follow the contours (that is, with minimum lateral grade).
Factsheet (.pdf): Questions and answers about drainage water management for the Midwest.
For more information about controlled drainage, visit the transforming drainage website.