T34 A Showcase of Undergraduate Research in Hydrogeology (Posters)

Sunday, 4 November 2018
9:00 AM - 5:30 PM
Halls J-K

THE EFFECTS OF LAND USE AND PRECIPITATION ON ROAD SALT RUNOFF IN PORTAGE CREEK, KALAMAZOO, MICHIGAN, USA

Paper number: T34-4
Program: Technical Sessions
Time: 9:00 AM – 5:30 PM

Authors

Abstract

Application of road salt is an effective means for maintaining safe driving conditions across the northern United States. Stormwater runoff containing dissolved road salt, however, has been identified as an emerging environmental issue. The state of Michigan, for example, uses 350 - 700 kilo-tons of road salt annually, and increased salinity due to runoff has been documented in a number of Michigan’s urban lakes and ponds. The effects of stormwater runoff on salinity in our local streams, creeks, and rivers that feed these bodies of water, however, has not been studied. To address this knowledge gap, the salinity of Portage Creek, a tributary of the Kalamazoo River in Kalamazoo County, Michigan, USA, was investigated. Seven sites located along Portage Creek were periodically sampled for salinity (conductivity), TDS, temperature, and turbidity in order to evaluate how land use and precipitation impact salinity in the creek.

The average salinity of Portage Creek increased from 0.25 to 0.40 ppt between the headwaters and the mouth. This increase correlates with an increase in the percentage of impervious surfaces within a 550 m wide buffer zone along the creek from its undeveloped (<20% impervious surfaces) headwaters to its urbanized (>20% impervious surfaces) mouth in downtown Kalamazoo. At several sampling points in late May 2018, salinity increased by 0.2 to 0.35 ppt following a heavy (>5 cm) rain event. A month later (early July 2018), the study was replicated to determine if rain events were still increasing salinity in the creek. The July 2018 results showed that baseline levels of salinity were about 0.1 ppt higher overall, but there was little to no increase in salinity following a smaller (<2.5 cm) precipitation event. All of these increases in salinity were observed months after the last application of road salt.

The results suggest that salinity increases as Portage Creek flows through more urban surroundings, and that salinity increases after rainfall events persist well after the last applications of road salt. Further study comparing salinity levels between fully rural streams and those that run through urban areas may explicitly identify the source of the increased salinity as road salt.

Geological Society of America Abstracts with Programs. Vol. 50, No. 6

doi: 10.1130/abs/2018AM-317797

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