ABSTRACT:

Hydrology and chemistry data for a spatially distributed synoptic and discharge campaign in the Augusta Creek Catchment (located in southwestern Michigan). The spatially distributed chemistry data was collected every 2-3 weeks from October 2021 to June 2024, and includes dissolved organic carbon (DOC), nitrate, sulfate, and chloride. Within 24 hours of collection samples were filtered through 0.45µm cellulose acetate membrane filters. We measured DOC (as non-purgeable organic carbon - NPOC), using two total organic carbon analyzers with total nitrogen units (Shimadzu TOC-V CPH with a TNM-1 and autosampler ASI-V before March 9 2023 and Shimadzu TOC-L CPH/CPN with a TNM-L ROHS and autosampler ASI-L after March 9 2023). For our analysis, we only include DOC/NPOC data after March 9 2023, due to discrepancies between the two instruments used. We measured anions (Cl-, NO3-, SO42-) using an ion chromatography system (Thermo Fisher Dionex, ICS1100 and ICS1000 and AS-DV autosampler). Our method detection limits were: 0.02 mg L-1 for anions and 0.43 mg L-1 for NPOC. Values that are "BDL" were below instrument detection limit. For values below method or instrument detection limit, we assigned concentrations of half the limit of quantification for the purpose of calculations and analyses. If this data is used in the future, values below the method detection limit will need to be filtered appropriately. Values that are NA were not analyzed. We collected discharge data during a period of baseflow from August 13-14, 2024 using two Sontek Flowtracker2 Acoustic Doppler Velocimeters. Discharge values were calculated using the Flowtracker’s mid-section method, measuring depth and velocity at ~20 stations across the stream width. Uncertainty in discharge (%) was also calculated by the Flowtracker instrument. To calculate specific discharge , we normalized our measured discharge by contributing area for each flow location.

This data supports the paper:
(DOI forthcoming)
Title: Wetlands, Groundwater and Seasonality Influence the Spatial Distribution of Stream Chemistry in a Low-Relief Catchment*
Abstract: Evaluating stream water chemistry patterns provides insight into catchment ecosystem and hydrologic processes. Spatially distributed patterns and controls of stream solutes are well-established for high-relief catchments where solute flow paths align with surface topography. However, the controls on solute patterns are poorly constrained for low-relief catchments, where hydrogeologic heterogeneities and river corridor features, like wetlands, may influence water and solute transport. Here, we provide an extensive, novel dataset of solute patterns in a low-relief wetland-dominated catchment to determine the dominant surface and subsurface controls, and wetland influence across the catchment. In this low-relief catchment, the expected wetland storage, processing, and transport is only apparent in solute patterns at small subcatchments. Meanwhile, downstream seasonal and wetland influence may be overwritten by large groundwater contribution to the stream. These findings highlight the importance of incorporating variable groundwater contribution into catchment-scale studies for low-relief catchments, and that understanding headwater wetland influence requires sampling across various spatial and temporal scales. In low-relief wetland-dominated catchments, solute patterns are influenced by a mosaic of controls, where stream chemistry is not solely driven by the dominant surface features and processes, but also by a previously under-explored large subsurface contribution.*
*Subject to change following peer-review