February 2012 Des Moines, IA

Drainage Water 

Management

Tile Systems With 

A Dual Function

Illustration courtesy of Agricultural Drainage Management Coalition

USDA-NRCS is an equal opportunity provider and employer.

Helping People Help The Land

@IowaNRCS

DWM Benefits

•	 Reduces loading of nitrates

and pesticides into the

drainage system and off the

farm

•	 Improves plant/crop

productivity & profitability

•	 Reduces oxidation of soil

organic matter

•	 Provides seasonal wildlife

habitat

•	 Prevents leaking of manure

into tile drains during land

application by raising riser

boards

Financial Assistance Available

Private landowners may be eligible

for technical & financial assistance

to implement DWM through the

Environmental Quality Incentives

Program (EQIP), which is managed

by USDA’s Natural Resources

Conservation Service (NRCS).

Iowa farmers may receive assistance

to create a drainage water

management plan, install control

structures, or manage the control

structures throughout the year.

Visit your local NRCS office for more

details.

www.ia.nrcs.usda.gov
DWM is an NRCS-approved

conservation engineering

practice. DWM holds water

in root zones when crops

need it and drains it when

there’s too much.

It manages

the timing and

amount of water

discharged from

agricultural

drainage systems. Unnecessary

subsurface drainage and nitrate

amounts leaving farm fields are

reduced, improving water quality.

With appropriate management,

DWM systems may also retain

water needed for late season crop

production.

To truly manage water table levels,

they simply retrofit an existing tile

system with a water control structure. Each structure controls an

elevation-defined area, based on

lay of the land and the tile system

layout already in place. Structures

are small, reasonably priced, and

operating instructions are fairly

simple:

Before tillage, remove riser

boards to drop water table

levels about 10 days prior to

planting fieldwork/operations.

During the growing season,

stack riser boards to potentially raise water table high enough

to provide capillary water to

crop root zone.

Before harvest, if needed,

remove boards to lower water

table 10 days before Fall fieldwork.

After harvest, install riser boards

to potentially raise water table

up even further–near ground

surface–to hold water and nutrients in the field/soil over winter.

Historically, subsurface drainage

(tile) made profitable crop production possible on Iowa’s flatter landscapes. One unwanted by-product

of this process is excess nutrients—

nitrates and phosphorous—that

ultimately enter creeks and streams

through tile drain water and negatively impact the environment. 

For years, talk of the Gulf of

Mexico’s “Dead Zone” pinned a

large portion of ecological blame

on agricultural production in the

Midwest. Agriculture has been

similarly targeted closer to home,

where amounts of nitrogen in

Iowa’s drinking water supplies have

increased dramatically throughout

the last century.

According to a 2000 U.S. Geological

Survey study, average annual nitrate

concentrations in the Des Moines

Looking Back

1

2

3

4

DWM Improves Water Quality

and Cedar Rivers have increased

nearly seven times over the last 100

years, from about 0.6 milligrams per

liter to as much as 4.6 milligrams per

liter. 

Now there is a way for farmers with

“flat” ground (.5 or 1% slopes and

flatter) to join the fight against

excess nitrate runoff by using

Drainage Water Management

(DWM) on their farms.

This system uses existing tile lines in

a way that makes them part of the

solution and not part of the problem.

DWM offers valuable options to

Iowa landowners with very flat

ground. These are the producers

NRCS conservation specialists and

Technical Service Providers (TSP)

can assist by developing Drainage

Water Management Plans.

For Example

In a 75-acre field with five control structures, a farmer would 

need to make about six trips 

per year to adjust elevation in 

the control structure.

NRCS Conservation Solutions...

Drainage Water Management