Watershed Symposium 2024

Summary:
This study aims to identify major phosphorus origins in Utah Lake’s watershed, quantify phosphorus influx from each source to Utah Lake, visualize HAB occurrences, and assess the correlation between phosphorus levels and HAB distribution.

Full Abstract:
This study aims to identify major phosphorus origins in Utah Lake’s watershed, quantify phosphorus influx from each source to Utah Lake, visualize HAB occurrences, and assess the correlation between phosphorus levels and HAB distribution. To accomplish this goal, our research team conducted in-situ water sampling and nutrient concentration measurements. We utilized geographic information systems (GIS) and remote sensing geospatial techniques to categorize key phosphorus sources to Utah Lake, employed empirical models to quantify nutrient runoff, and leveraged Google Earth Engine (GEE) and ArcGIS Pro to automate the processing of Landsat images for visualizing HAB distribution in Utah Lake. The identified key nutrient sources include urban lawns, golf courses, parks, herbaceous, deciduous forest, evergreen forest, mixed forest, hay/pasture, and cultivated crops. Their respective total areas ranged from 9.5 km² to 1,775.7 km², with golf courses being the smallest and deciduous forests being the largest. Notably, urban lawns and cultivated crops, covering 337 km² and 344.41 km2, emerged as two significant phosphorus sources to Utah Lake, despite constituting only 7.5% and 7.6% of the total Utah Lake Watershed area, respectively. Furthermore, our analysis revealed a close correlation between HAB distribution and phosphorus levels in the lake. Prior studies on Utah Lake have focused primarily on phosphorus loading from wastewater treatment plants (WWTPs) and atmospheric deposition. While WWTPs are still the major phosphorus contributors to the occurrence of HABs, our findings suggest that land-derived non-point nutrient sources play a substantial role in triggering HABs in Utah Lake.