Water Resources Engineering (WRE) connects engineering hydrology and hydraulics with global, economic, environmental, and societal issues. Our student Sara Chin makes this connection here…

The news entitled, “Agricultural tile drains – beneficial for crops or costly to environment?” was reported by the Press Republican in their January 26, 2014 online news. The news relates to the WRE domain of hydraulics and the specific issue of the movement of water due to tile draining in agricultural land and the quality of water at discharge points. In summary, tile drainage is commonly used in agriculture to reduce the amount of water in agricultural fields. This practice results in higher crop yields as the lowered water table prevents the roots from becoming waterlogged. When drains are placed in the soil below the water table, groundwater flows into the drain and towards discharge points. Discharge points tend to be streams or rivers. Historically, tile drains have been made out of materials such as stones, straw, and brush. Today, the pipes typically consist of plastic. It has been found that tile draining may cause nutrient loading in streams and other discharge points, especially in fields where fertilizers high in nitrates and phosphorous are used. Nitrate and phosphorous in soil tend to be fixed when water remains stationary; however, when water is being drained, some of the nutrients will wash away and follow the water into discharge points. High concentrations of these nutrients downstream may lead to ecological injury by eutrophication. It is still being studied whether tile draining generally produces a significant amount of nutrient discharge. The amount of nutrient discharge per site depends upon the type of soil within and surrounding the agricultural field. Soil that is prone to cracking, such as heavy clay soil, should be avoided. Best management practices should be followed when managing agricultural land.

Because agriculture occupies a great amount of land in the United States, the effects of tile draining accumulate as more farms emerge and implement this type of water management. Unfortunately, most of the land that undergoes tile draining are wetlands. The article could have elaborated on the importance of wetland hydrology and the ecosystem services that wetlands provide. In “Recognizing Ecosystem Services from Wetlands of International Importance: An Example from Sussex, UK,” McInnes identifies regulatory, provisional, and cultural services provided by several specific wetlands. Eliminating wetland hydrology and replacing it with what would most likely be intensive monoculture agricultural fields removes those ecosystem services in exchange for provisional services that are more costly to sustain.

Overall, tile drainage has facilitated the work of farmers and resulted in the production of a high crop yield to feed a growing population. However, it can cause the devastation of wetlands that provide critical ecosystem services and, under certain soil conditions, can lead to water quality problems. If the amount of fertilizer used in agriculture was reduced, then the amount of nutrient discharge may decline. If wetlands ceased to be drained to make way for agricultural fields, then the amount of ecological damage from tile draining may also decline.

Tile drainage diagram from the USGS.

Tile drainage diagram from the USGS.

References

Tile Drainage. N.d. Image. USGS. US Dept of Interior. Web. 26 Jan. 2014. <http://pubs.usgs.gov/fs/2009/3042/images/fs20093042_fig02.png>.

Winslow, Mike. “Agricultural Tile Drains — Beneficial for Crops or Costly to Environment?” Press Republican. N.p., 26 Jan. 2014. Web. 26 Jan. 2014. <http://www.pressrepublican.com/0105_outdoor_perspective/x651195444/Agricultural-tile-drains-beneficial-for-crops-or-costly-to-environment>.

McInnes, R. J. “Recognizing Ecosystem Services from Wetlands of International Importance: An Example from Sussex, UK.” Wetlands 33.6 (2013): 1001-017. Web of Science. Web. 26 Jan. 2014. <http://link.springer.com/article/10.1007%2Fs13157-013-0458-1/fulltext.html>.

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