60-32 Understanding Phosphorus Load Trends and Controlling Factors in Illinois Watersheds.

Session: 2YC and 4YCU Geoscience Student Research Poster Showcase

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Abstract:

Phosphorus pollution in Illinois watersheds has become an increasingly critical issue, with recent studies revealing rising concentrations in streams and rivers. This escalation poses serious threats to water quality, aquatic ecosystems, and human health. Phosphorus is a key water quality constituent of concern because it often serves as the limiting nutrient in freshwater systems. When present in excess, it triggers eutrophication—a process that leads to rapid algal growth, degraded water quality, reduced dissolved oxygen concentrations (hypoxia), and harmful ecological impacts such as fish mortality. According to the 2023 Illinois Nutrient Loss Reduction Strategy biennial report, phosphorus levels increased in 2021 and 2022 compared to historical baseline data, with the Illinois River Basin identified as a significant contributor to phosphorus loads entering the Gulf of Mexico. Understanding the factors influencing phosphorus loads in Illinois watersheds is essential, as these waters ultimately flow into the Gulf, contributing to hypoxic conditions. This project aims to investigate phosphorus load trends and identify key contributing factors within Illinois watersheds. These factors include watershed characteristics (e.g., area, perimeter), climate variables (precipitation, temperature), hydrological metrics (discharge), anthropogenic influences (e.g., point source pollution), land use, and soil composition. Historical water quality data will be analyzed using non-parametric methods such as the Mann-Kendall trend test and Sen’s slope estimator to detect and quantify trends in phosphorus concentrations. A comprehensive database of these factors will be developed for each watershed, followed by a data exploration analysis using machine learning to assess controlling influences. We expect to observe a positive trend in phosphorus loads in regions characterized by high precipitation, extensive urban runoff, and intensive agricultural activity. Insights from this study will support the development of targeted strategies to mitigate phosphorus pollution, protect water quality, and sustain ecological health in Illinois watersheds.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8393

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