Basal Resource #2: Water

by awest6 on April 16, 2015 - 4:43pm

Clean water is as important to human health and survival as fresh food, but unfortunately, these two resources are locked in competition. During the year 2004, agriculture was a leading source of water quality impairment, accounting for degradation of approximately 94,000 miles of streams and 1,670,513 acres of open water (EPA 2009). Sources of this decline in water quality are pollution, sedimentation, and depletion.

Main agricultural water pollutants are nitrogen, phosphorous, pesticides, hormones, and antibiotics. Fertilizers and manure are spread on fields as a method of increasing crop yields, but are often applied in higher quantities than necessary. Phosphorous and nitrogen not taken up by plants are washed into water sources, where they cause algal blooms which deplete oxygen, contribute to fish kills, and introduce toxins into the water (Sustainable 2012). Ammonia, nitrates, and pesticides are additional toxins which enter water bodies from agricultural fields (Sustainable 2012).

Manure spreading and rupture of manure holding tanks also releases pathogens, hormones, and antibiotics into the water bodies. Pathogenic microorganisms from manures such as Salmonella and E. Coli can cause over 40 diseases in humans (NRDC 2013). Of the antibiotics administered, anywhere from 75-90% are passed through the body and excreted (Sustainable 2012). Associated problems are the cultivation of bacterial colonies resistant to antibiotic treatment (Sustainable 2012). Hormones have detrimental effects on the reproduction of fish species, and can remain active in waters for up to 270 days after being expelled from livestock (Sustainable 2012).

 Soils washed or blown away from improperly managed agricultural fields become problematic when deposited into water bodies, increasing sedimentation. This influx of soil particles into a water body affects aquatic organisms by reducing light penetration, importing heavy metals, and altering microhabitats (EPA 2012). Reductions in the amount of light filtering into water causes declines in aquatic plants and photosynthetic plankton (EPA 2012). Heavy metals are toxic to many fishes and aquatic invertebrates, resulting in their death. Sediments also fill interstitial spaces, which are crucial for fish spawning and refuge for a number of invertebrates. (EPA 2012)

Agricultural processes use approximately 70% of available freshwater, in comparison with industrial and municipal uses of 20% and 10% respectively (FAO). A majority of this water is withdrawn from groundwater aquifers, which have been plundered at a faster rate than they are replenished. Irrigation practices are generally faulty, resulting in a loss of up to 60% due to leaks and evaporation, before water ever reaches the crops it is intended to replenish (FAO). Water that is then returned to streams, rivers, lakes, etc. is distributed differently, and clogged with the pollutants discussed above. 

References:

Environmental Protection Agency (EPA). 2012. Managing nonpoint pollution from agriculture. United States Environmental Protection Agency, Nonpoint Source Control Branch. Available at: http://water.epa.gov/polwaste/nps/outreach/point6.cfm

Environmental Protection Agency (EPA). 2009. National water quality inventory: report to congress. United States Environmental Protection Agency, Office of Water. Available at: http://water.epa.gov/lawsregs/guidance/cwa/305b/upload/2009_05_20_305b_2...

Food and Agriculture Organization (FAO). N/A. Depletion of fresh water resources. Food and Agriculture Organization. Available at: http://www.fao.org/ag/againfo/programmes/en/lead/toolbox/Indust/DFreWat.htm

Natural Resources Defense Council (NRDC). 2013. Facts about pollution from livestock farms. Available at: http://www.nrdc.org/water/pollution/ffarms.asp Sustainable Table. 2012. Water quality. Grace Communications Foundation. Available at: http://www.sustainabletable.org/267/water-quality

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