T127 Human Impacts on the Hydrologic Cycle (Posters)

Monday, 10 October 2022
2:00 PM - 6:00 PM
Exhibit Hall F

TRENDS IN NUTRIENT LOAD AND DRIVING FACTORS IN THE ILLINOIS RIVER BASIN

Paper number: T127-5
Program: Technical Sessions
Time: 2:00 PM – 6:00 PM

Authors

Abstract

The demand for clean and potable water increases as population grows, surface water serves as water supply source to many municipalities. However, the quality of surface waters is altered as result of excess load of nutrients into these waterbodies. For example, excess nitrate and dissolved phosphorus in water leads to eutrophication. This study seeks to understand the various factors driving nutrient trends in the Illinois River basin with focus on nitrate and dissolved phosphorus. The 2019 bi-annual report from Illinois Nutrient Loss Reduction Strategies reported that there were about 13% and 35% increases in nitrate and total phosphorus, respectively, across the statewide basins compared to the previous baseline of 1980-1996.

This study assessed the trends in nutrient loading in the Illinois river basin and the factors driving such as climate (precipitation), hydrology (discharge), and land use. To analyze the trend, we used historical nutrient data from various sources including USGS. First, load was estimated using simple and multiple linear regression models using LOADEST (LOAD ESTimator) package developed by USGS in a R programing interface. The purpose is to produce accurate load estimate and obtain continuous load data later used for trend analysis. A non-parametric Mann Kendall test and Sen’s slope test were adopted to analyze and detect trends. Further, cross correlation was employed to understand the relationship between watershed characteristics and trends in nutrient load. The preliminary result of the load estimation model, the Reg model (9) in the LOADEST shows the best fit across multiple stations with R2 values between 0.57 and 0.92 ), and estimated mean flux rate of the point predictions of nitrate to be 39,400-234,000 kg/d and dissolved phosphorus range from 46200-375,000 kg/d. Stations which shows a positive trend for both nitrate and dissolved phosphorus loads coincides with stations with increasing trends of discharge, precipitations, and land use regions with much developed medium to high intensity. The results from this study will aid better water quality management.

Keywords: LOADEST, Water Quality, Nutrients, Cross Correlation, Illinois River.

Geological Society of America Abstracts with Programs. Vol. 54, No. 6

doi: 10.1130/abs/2022AM-379270

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