45 Hydrogeology (Posters)

Added due to amount of discipline abstracts submitted.

Wednesday, 11 March 2026
9:00 AM - 12:00 PM
RCC, Lower Level Hall

Lake Maumelle as a Protected Source-Water Baseline for Watershed Health Assessment in Central Arkansas

Paper number: 45-5
Program: Technical Sessions
Time: 9:00 AM – 9:00 AM

Authors

Abstract

The Lower Arkansas-Maumelle HUC-8 watershed serves nearly 500,000 people for drinking water, agriculture, and industry across 1,100 square miles in central Arkansas, including the state capitol of Little Rock. Lake Maumelle forms the forested headwater of this HUC-8 watershed and serves as the region’s primary drinking-water reservoir. Lake Maumelle is managed as a protected source-water area and can serve as a headwater reference condition for distinguishing natural seasonal variability from watershed-scale degradation, providing context for downstream water quality changes that affect ecologically sensitive wetland-associated aquatic ecosystems. 

Over a three-year monitoring program, University of Arkansas at Little Rock students collected field measurements and water samples at four tributary sites feeding directly into Lake Maumelle and one outflow site draining toward the Arkansas River. Field parameters included temperature, turbidity, pH, specific conductance, dissolved oxygen, and flow velocity. The Arkansas Water Resources Center analyzed samples for nitrogen (ammonia-N and nitrate+nitrite-N), total phosphorus, soluble reactive phosphorus, total dissolved solids, total suspended solids, and quarterly indicators, including microbiological and metal parameters. Using GIS software, inverse distance weighting (IDW) was employed as the data visualization technique to create concentration heatmaps for each parameter and sampling date. Visualization techniques include using script-based automation workflows to generate hundreds of maps representing each sampling event and analysis parameter. 

These analyses reveal temporal trends and spatial relationships associated with downstream versus upstream conditions. Across all sites, measured concentrations were generally within EPA drinking-water benchmark ranges used here for screening-level context. Although most water quality chemical indicators were within benchmark ranges, the downstream outlet site exhibited maximum ranges of up to 2x nitrogen and phosphorus species relative to the four tributary sites. These elevated ranges are relevant for monitoring disruptive algal blooms driven by eutrophication. Through this monitoring, water quality characterization can be established for a protected reference system, providing a baseline against which degradation in urban and agricultural portions of the watershed can be measured. This source-water baseline framework transforms routine monitoring into an interpretable watershed health metric, supporting public communication, targeted follow-up sampling, and comparison of downstream impairment relative to protected headwater reference behavior.

Geological Society of America Abstracts with Programs. Vol. 58, No. 1

doi: 10.1130/abs/2026SE-411792

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