An index for inferring dominant transport pathways of solutes and sediment: Assessing land use impacts with high-frequency conductivity and turbidity sensor data

Amirreza Zarnaghsh; Admin Husic

doi:10.1016/j.scitotenv.2023.164931

An index for inferring dominant transport pathways of solutes and sediment: Assessing land use impacts with high-frequency conductivity and turbidity sensor data

Sci Total Environ. 2023 Oct 10:894:164931. doi: 10.1016/j.scitotenv.2023.164931. Epub 2023 Jun 20.

Authors

Amirreza Zarnaghsh¹, Admin Husic²

Affiliations

¹ Department of Civil, Environmental and Architectural Engineering, University of Kansas, United States of America.
² Department of Civil, Environmental and Architectural Engineering, University of Kansas, United States of America. Electronic address: ahusic@ku.edu.

PMID: 37343889
DOI: 10.1016/j.scitotenv.2023.164931

Abstract

Land use change threatens aquatic ecosystems through freshwater salinization and sediment pollution. Effective river management requires an understanding of the dominant hydrologic pathways of sediment and solute delivery. To address this, we applied hysteresis analysis, hydrograph separation, and linear regression to hundreds of events across a decade of specific conductance and turbidity data from three streams along a rural-to-urban gradient. Thereafter, we developed an index (β_runoff^') to quantify the relative influence of surface runoff to event-scale suspended sediment generation, where a value of '1' indicates complete alignment of suspended sediment generation with the temporal structure of runoff whereas '0' indicates total alignment with baseflow. Solute hysteresis results showed a predominance of dilution for the rural and mixed-use streams irrespective of road salt presence. On the other hand, urban stream behavior shifted from dilution to flushing following salt application, which was largely driven by greater runoff coefficients and the connectivity of distal solutes to the stream corridor. The newly developed index (β_runoff^') indicated that suspended sediment dynamics were more aligned with runoff in all three streams: rural stream (β_runoff^' = 0.70), mixed stream (β_runoff^' = 0.57), and urban stream (β_runoff^' = 0.64). The relative importance of baseflow to sediment generation grows slightly in urbanizing streams, as impervious surfaces disconnect upland sediment, which would otherwise transport with runoff, while piston-flow baseflow erodes exposed streambanks. Our findings emphasize the need to consider the impact of human modification of the landscape on solute and sediment transport in freshwater systems for effective water quality management. Further, our β_runoff^' index provides a useful tool for assessing the relative influence of surface runoff on event-scale solute or sediment generation in streams, supporting river management and conservation efforts.

Keywords: Baseflow; Freshwater salinization; Hydrologic connectivity; Hysteresis; Runoff; Sediment transport.