Empirical Relationships between Water Quality and Agricultural Land Use in Rural Maine

Anthropogenic eutrophication of freshwater lakes due to land use change is a growing global problem with economic consequences, such as a reduction in shoreline property value. Managing eutrophication is of utmost importance in Maine, USA due to the large number of inland fresh waterbodies and their economic importance for fisheries, recreation, and real estate. This thesis investigates the relationships between water quality and catchment land use. Agricultural land use is a large driver of excess nutrient export to lakes, including in Maine, and can result in toxic cyanobacterial blooms, decreased water clarity, and fish kills. I developed a statistical relationship to quantitatively link agricultural intensity in the catchment and resultant water quality outcomes in Maine lakes. I observe a strong statistical relationship between water quality and anthropogenic activity in the catchment, as expected. Interestingly, I found that the effects of anthropogenic activity were most closely related to a five-year lag in water quality, which is between 0.8 to 4.71 years longer than the lake residence times. My results suggest that changes in land use may have long-term effects on water quality that last for far longer than would be expected. The analysis presented in this paper is novel for directly linking long term observational agricultural and biological datasets and presents a new way to quantitatively link water quality and anthropogenic intensity in the catchment area.