The Great Lakes contain 20 percent of the world’s freshwater (McBean 2008) and are already facing the impacts of anthropogenic climate change. The Greats Lakes have seen a 10 to 25 percent increase in precipitation from 1981 to 2010 (NOAA, 2019) due to increased evaporation. The amount of precipitation is predicted to increase by 12.5 percent by 2080 (Wang 2016). Increased rainfall has led to increased nutrients washed out of soils, as found in two studied watersheds (Wang 2018). In one watershed the amount of phosphorus washed out, due to soil erosion, could increase by 108 percent by 2099 (Ibid). These additional nutrients can result in nutrient loading and therefore algae booms and eutrophication in the Great Lakes.
One reason for the increased precipitation is the reduction in ice cover, which results in more evaporation. Ice cover has decreased by 71 percent on the Great Lakes from 1973 to 2010 (Collingsworth, 2017). Many commercially important fish species allow their eggs to overwinter below the ice, with reduced ice cover their eggs are more susceptible to wave action damage (Ibid). Models to predict how much ice coverage will be reduced vary widely but they all agree that the coverage will reduce by 2050. One initial benefit of reduced ice cover is that it will reduce the number of winter kills as there will be more circulation of oxygen.
The following was my environmental studies senior thesis.
Storm water runoff from agricultural areas carries excess nutrients with it, which leads to dead zones in nearby lakes. Lake Champlain is the sixth largest lake in the United States, and is facing issues related to excess nutrients from farms. Research related to farms has focused on runoff related to manure spread on fields. One area not previously addressed is manure management on farms. There are two main types of manure pit styles on dairy farms; enclosed and, unenclosed. Three farms of each of these types were analyzed for nutrient runoff during storm events. Four key factors linked to nutrient runoff were analyzed through field sampling; phosphorus, dissolved oxygen, nitrate, and ammonium. The study took place in the Lamoille River Watershed in Vermont which feeds into Lake Champlain. Baseline data was collected before storms and samples were also collected after storms. The goal of this study was to identify a manure pit management style that minimizes nutrient runoff. While the data indicated that a manure pit that lacked a confining wall impacted phosphorus, ammonium, and nitrate, there was no significant impact on dissolved oxygen from such pits. However, manure pits had relativity low impact on the streams overall; other more important factors may be soil erosion, manure spreading, and septic tanks.