Ag Drainage Definitions

Blind Inlet

An area of tightly spaced, shallow tile typically installed in a low-lying area to remove surface water quickly while filtering through soil, rock, or other porous material, preventing soil and debris from washing into the tile system.

Controlled Drainage

A practice where the water table in a field is managed or “stair-stepped” to match the field’s topography via control structures and/or watergates.


A natural process where nitrates in water is converted into nitrogen gas. Typically occurs in low-oxygen, saturated conditions in the presence of carbon and denitrifying bacteria.

Denitrifying Bioreactor

An edge-of-field water quality BMP where the water from a tile system is routed through an underground bed of woodchips, or other carbon source, that converts nitrates in the water into nitrogen gas.

Denitrifying Wetlands

Strategically placed wetlands in low, wet, unproductive areas where water can be collected and treated before it continues downstream.

Drainage Coefficient

The depth amount of water designed to drain from a given area in 24 hours. Typically ¼” to ½” depending on crop rotation and precipitation patterns.

Drainage Water Management

General term for systems that manage subsurface water on agricultural land; Encompasses conventional drainage, controlled drainage, subirrigation, groundwater recharge, water quality practices, etc.

Drainage Water Recycling

A practice where drainage water is collected and stored during times of excess moisture (typically in the spring) where it can be used as irrigation water later in the growing season.


Referred to as ET, is a combination of evaporation of water into the air as well as water used by the crop (transpiration).

Flow Rate (Q)

Volume of water transported over a given time.

Hydraulic Conductivity (Ksat)

Also known as “Saturated Conductivity”. A characteristic of soil reflecting how fast water can move through it. Commonly expressed in in/hr, ft/day, or micrometers/second


Perforated tile lines that collect water from saturated soil, feeds into a larger mainline pipe, then flows to a system’s outlet.


The outflow point of a drainage system. Typically, a pipe flowing into a ditch, stream, or wetland, but can be a lift station that pumps water from the subsurface system into a ditch if there’s not enough slope for a gravity system.

Riparian Buffer

Area between a crop field and a ditch or stream; typically planted to native prairie vegetation to reduce soil erosion and filter surface runoff before it gets to the stream.

Saturated Buffer

An edge of field water quality BMP where water from a tile system is routed into perforated tile lines running parallel to a waterway under a riparian buffer. The organic matter in the buffer filters and denitrifies the water before it reaches the stream.


A condition that occurs when 100% of the soil pores are filled with water, displacing any naturally occurring pockets of air, needed for plant growth.

Subsurface Irrigation

Similar to Controlled Drainage, but water is supplied to the system to ensure the water table is always at the optimal level.

Water Control Structures

An inline structure that uses stoplogs to dam water to raise the water table upstream to a desired level. Stoplogs are managed throughout the growing season to keep the water table at the right height relative to the crop root depth.