Analysis of Long-Term Chlorophyll Trends in Utah Lake using Landsat Data and Lake Regions

Abstract

Understanding long-term trends in water quality is essential for effective and sustainable management of waterbodies. Using remotely-sensed data, we generated and analyzed a 40-year history of estimated chlorophyll-a (chl-a) concentrations on Utah Lake, which experiences intense algal blooms and is currently the subject of significant controversy over potential remediation strategies. To investigate the potential impacts of shoreline development and WWTP effluent streams on chl-a concentration, which is an indicator of algal biomass, we compared trends and average concentration estimates for different regions of the lake. For the majority of the lake, there is a very small, statistically significant decreasing trend in chl-a concentrations over the last 40 years, and regions receiving WWTP effluent show little difference from regions with undeveloped shoreline. One region (a shallow bay isolated from the rest of the lake) has both higher average concentrations and a significant positive trend over the 40 years, and appears to be influencing the areas of the lake connected to it. These results indicate that other factors besides nutrient inflows are likely driving algal blooms on Utah Lake, and further research is necessary to understand the lake processes and characteristics that influence these blooms.