Understanding the spatial and temporal distribution of water quality variables in lakes is vital for assessing their overall health. So vital in fact, that numerous government agencies are tasked with testing and maintaining a healthy public surface water supply. This study focuses primarily on the efficacy of one of such agency’s procedure for monitoring surface water quality. The Minnesota Pollution Control Agency’s (MPCA) procedure for water quality testing does not account for neither the spatial nor temporal variability of water quality in small Minnesota lakes, including the lake at the center of this study, Bass Lake. Currently, the MPCA assumes spatial homogeneity of water quality parameters by utilizing a singular sampling site to represent the totality of small Minnesota lakes with simple shoreline silhouettes. The MPCA’s monitoring procedure is incapable of measuring the up to 54% spatial disparity in trophic state observed through in-situ sampling at different spatial positions on Bass Lake. Additionally, because the MPCA samples water from lakes on a schedule developed months in advance, they are unable to sample during the most significant periods of poor water quality. This oversite can cause them to severely underestimate the trophic state of a body of water and was demonstrated in the 2019 sampling season when only two days after an MPCA sampling event, a large algae bloom severely distorted a number of water quality parameters. This poses not only an economic concern but also, a public health concern. Bass Lake in Faribault County, Minnesota was studied repeatedly by the MPCA throughout the 1980’s to the early 2000’s and has had mixed results ranging from a hypereutrophic to mesotrophic lake. Bass Lake serves as an ideal candidate for this study given its simple bathymetric topography, uncomplicated shoreline, heavily agricultural land use, and geomorphic history. Changes in water quality were measured using Carlson trophic state index values derived from Secchi disk transparency, total phosphorus, and chlorophyll-a concentration measurements derived via water sampling and laboratory testing. Additionally, this study attempts to determine the capability of multi-rotor UAV mounted multispectral imagers to determine the concentration of chlorophyll-a remotely.
Date of Degree
Master of Science (MS)
Social and Behavioral Sciences
Lott, O. (2021). Comparative analysis of water quality monitoring procedures in a small, eutrophic lake, South-Central Minnesota [Master’s thesis, Minnesota State University, Mankato]. Cornerstone: A Collection of Scholarly and Creative Works for Minnesota State University, Mankato. https://cornerstone.lib.mnsu.edu/etds/1190/
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