A paper published in the December 2016 edition of PLOS ONE, a multidisciplinary research journal, provides useful context for water quality discussions. Based on data collected from 2007 to 2013 from a Discovery Farm location in Kandiyohi County, “Comparison of Contaminant Transport in Agricultural Drainage Water and Urban Stormwater Runoff” quantifies and compares sediment, phosphorus and nitrogen losses from both farm fields and urban lands representative of the region.
This long-term analysis reinforces the importance of addressing potential pollution issues in both urban and agricultural landscapes while also noting that the areas of concern are different between the two. The paper concludes that management practices should be directed to load reduction of ammonium and total suspended solids from urban areas, and nitrate from cropland, while phosphorus should be a target for both.
Given the extent to which urban areas continue to grow while cropland area shrinks, this information serves as a helpful reminder that barring some dramatic new breakthrough in technology or engineering, water quality efforts need to account for some unavoidable impacts due to both land uses. Caution must be exercised in scaling up the results or applying them to other watersheds or different climate conditions, though the study period did include a range from relatively wet to dry year. Readers may also be surprised to note that the ratio of cropland to urban area in the studied watershed is 4.6:1, much lower than often presumed. For comparison, the statewide ratio is 5.8:1.
See the full article at: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0167834.