Abstract
Freshwater eutrophication typically driven by non-point source phosphorus pollution is one of the worlds’ most prevalent and vexing environmental problems with the Laurentian Great Lakes on the Canada – United States border. During 1975 – 1977, the Pollution from Land Use Activities Reference Group examined eleven agricultural watersheds in order to investigate the impacts of land use activities on surface water quality. This study examined how agricultural land use and management has transformed in two watersheds, Nissouri Creek and Big Creek. The goal of this study was to quantify the phosphorus mass balance change within the watersheds. During 2015 – 2019 land use and management practices survey data was collected. Results of this study showed Nissouri Creek is now depleting -2.19 kilograms of phosphorus per hectare of agricultural land, while Big Creek is still accumulating 4.77 kilograms of phosphorus per hectare of agricultural land. This study can guide efforts to limit the long-term losses of phosphorus in the Laurentian Great Lakes and elsewhere.
Highlights
Great Lakes water quality has always been a concern for both Canada and the United States
Big Creek is almost entirely composed of cash crops with corn, soybeans, and grains making up approximately 99% of the crops grown in the present day and 96% of the crops during the 1974 – 1976 time period
This study looked at fertilizer applications, manure applications, crop removals, and stream losses of phosphorus within two watersheds over two time periods separated by ~40 years
Summary
Great Lakes water quality has always been a concern for both Canada and the United States. The emergence of dead zones and algal blooms in Lake Erie and other Great Lakes in the 1960’s led the Canadian and the United States Governments to sign the Great Lakes Water Quality Agreement (GLWQA) on April 15, 1972 (GLWQA, 1972). The agreement requested the International Joint Commission (IJC) to investigate pollution of the boundary waters of the Great Lakes system from agricultural, forestry and other land use activities (GLWQA, 1972). Algal blooms were mitigated in the 1970’s by the control of point sources, with Lake Erie responding quickly by a measurable decrease in total phosphorus (TP) concentrations (Dolan, 1993; Scavia et al, 2014). With the reemergence of algal blooms in Lake Erie in the mid 1990’s and worsening in the early 2010’s (Scavia et al, 2014) there was renewed interest in the relationship between land use and nutrient losses. There are the previously cited studies looking at Ohio loadings to Lake Erie and the Great Lakes, but there is little research on the Canadian side of Lake Erie
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