Drainage Facts

Facts about drainage and drainage districts

1) What is drainage?

Drainage is the removal of water from the soil profile by natural or artificial means. Drainage uses underground pipes and open ditches to carry water away from cropland during periods of excess moisture.

2) What are drainage districts?

Natural drainage outlets are not always available or accessible for all lands that need them in a particular watershed. Use of a natural outlet that is adequate in capacity and depth to carry the runoff may require the extension of drainage outlets into land owned by others. These other landowners may benefit from these types of extensions. Similarly, a system of levees is often required to protect land from flooding. Drainage districts provide a legally organized means to construct and maintain adequate drainage outlets and levees. According to Iowa law – “The drainage of surface waters from agricultural lands and all other lands or the protection of such lands from overflow shall be presumed to be a public benefit and conducive to the public health, convenience and welfare.”

3) How are drainage districts formed?

Two or more contiguous landowners can petition the respective county Board of Supervisors to create a drainage district.

4) Who manages drainage districts?

Iowa law is unique nationally on how this is done. Once a district is created, the Board of Supervisors of the county in which the district is located becomes the board of trustees (managing board) for that district. If a district chooses to do so, it can “opt out” of Board of Supervisor management and elect its own trustees. Most districts are managed by Boards of Supervisors.

5) Who pays for drainage districts?

Lands within the confines of an established drainage district can be assessed for the construction, maintenance and repair of drainage district facilities. Assessments are based on the relative benefits received and may be spread over several years.

6) How many drainage districts are there in Iowa and where are they located?

There are more than 3,000 districts in the state. Most are located in north central and northwest Iowa although there are also districts bordering the Missouri and Mississippi Rivers.

7) How much of Iowa is drained land?

It is estimated that more than 9 million acres of the state are drained. That would constitute almost 26% of the state’s land mass. 9 million acres is larger than the combined land mass of the states of Massachusetts, Connecticut and Rhode Island.

8) What is the Iowa Drainage District Association?

IDDA is a private, non-profit organization existing solely for the benefit and protection drainage districts. IDDA is incorporated with the state of Iowa. Our federal non-profit tax status is 501 (c) 6. IDDA is provided for in the Iowa Statutes Section 468.176. which states that “Levee or drainage districts are authorized to become members of drainage associations for their mutual protection and benefit, and may pay dues and membership fees therein out of their maintenance funds.”

9) Where in the Iowa Code are the drainage laws?

The drainage statutes are quite extensive and cover almost 75 pages of the Code book. The drainage statute is Chapter 468. Also, the state apparently saw the importance of agricultural drainage early in the 20th century as there was language added to the constitution on drainage. Article I, Section 18 of the Iowa Constitution states that “The general assembly, however, may pass laws permitting the owners of lands to construct drains, ditches and levees for the agricultural, sanitary or mining purposes across the lands of others, and provide for the organization of drainage districts, vest the proper authorities with power to construct and maintain levees, drains and ditches and to keep in repair all drains, ditches and levees heretofore constructed under the laws of the state, by special assessments upon the property benefitted thereby. The general assembly may provide by law for the condemnation of such real estate as shall be necessary for the construction and maintenance of such drains, ditches and levees, and prescribe the method of making such condemnations.” This constitutional provision was added in 1908.

10) Do all drainage districts use gravity solely as a means for moving water?

No, there are other districts in southeast Iowa by the Mississippi River that use an elaborate system of pumping stations. These districts have their own section of the drainage laws. By far the most prevalent systems however rely on gravity and the old axiom that water flows downhill.

11) What about districts that have land in more than one county – how are they managed?

In such cases, district management decisions would be made by both county boards of supervisors acting jointly. In essence, the two county boards would become one for drainage purposes. For ease of administration, a “lead” county is usually designated.

12) How long have drainage districts been in existence?

Most of the drainage district statutes were written in the early 1900’s and the creation of many of today’s districts followed close behind that. The long history of the districts is both a blessing and a disadvantage. It is a blessing in that drainage of land has given us decades of productive agriculture that would not have been possible without it. It is a disadvantage in that much of the drainage infrastructure is very old and will have to be replaced – at substantial cost to the landowners in the district.

Production and Environmental Benefits of Drainage

Increased yields – Research varies as to how much of an increase there is. A comprehensive twenty year study done in Canada showed a 29% average increase in corn yields on tiled vs. non-tiled land and a 26% increase in soybean yields. A ten years study done in Ohio showed a corn yield increase due to drainage of 40 bushels per acre.

Plant roots receive enough oxygen to mature properly

Soil surface temperatures are increased which helps seeds germinate

Plants roots are grown deeper into the soil so they can absorb more nutrients

Water damage to public roads is inhibited

Storm water runoff is absorbed and downstream flooding is reduced

The chances of water-borne diseases are reduced

Since the soil can absorb and store more rainfall, runoff from the soil surface is reduced. Thus, soil erosion is reduced

Since fields dry out more quickly with drainage, the number of days available for planting and harvesting crops is increased

Crop loss due to drowning is decreased

Land values are increased

Soil structure is improved. Soil needs to be drained to avoid soil compaction and structural damage, both of which reduce yields.

Soil bearing strength is increased. The bearing strength of soil depends on its water content which in turn is affected by the depth of the water table. Good soil drainage increases soil strength and reduces damage caused by farming operations.
Promotes energy-conserving efficient farming practices and facilitates no-till and conservation tillage methods

Reduced losses of sediments, phosphorus, ammonium-nitrogen, pesticides, micro-organisms and anti-biotics