Stream chemistry and hydrology data in the Augusta Creek catchment: a low-relief, wetland-rich catchment in Michigan

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:
Weidner, C. R., Zarnetske, J. P., Kendall, A. D., Martin, S. L., Nesheim, S., & Shogren, A. J. (2025). Wetlands, groundwater and seasonality influence the spatial distribution of stream chemistry in a low‐relief catchment. Journal of Geophysical Research: Biogeosciences, 130, e2025JG008989. https://doi.org/10.1029/2025JG008989

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 a data set of solute patterns from 58 synoptic surveys across 28 sites and over 32 months in a low‐relief wetland‐rich catchment to determine the major surface and subsurface controls along with wetland influence across the catchment. In this low‐relief catchment, the expected wetland storage, processing, and transport of solutes is only apparent in solute patterns of the smallest subcatchments. Meanwhile, downstream seasonal and wetland influence on observed chemistry can be masked by large groundwater contributions to the main stream channel. These findings highlight the importance of incorporating variable groundwater contributions into catchment‐scale studies for low‐relief catchments, and that understanding the overall influence of wetlands on stream chemistry requires sampling across various spatial and temporal scales. Therefore, in low‐relief wetland‐rich catchments, given the mosaic of above and below ground controls on stream solutes, modeling efforts may need to include both surface and subsurface hydrological data and processes.

本数据集为密歇根州西南部奥古斯塔溪流域（Augusta Creek Catchment）的空间分布式同步水文与水质观测及流量监测数据。
空间分布水质数据的采集周期为2021年10月至2024年6月，每2~3周开展一次，检测指标涵盖溶解性有机碳（Dissolved Organic Carbon, DOC）、硝酸盐、硫酸盐及氯化物。样品采集后24小时内，采用0.45μm醋酸纤维素膜过滤器对样品进行过滤。
本研究采用两台搭载总氮模块的总有机碳分析仪测定溶解性有机碳（以不可吹扫有机碳Non-Purgeable Organic Carbon, NPOC计）：2023年3月9日前使用岛津（Shimadzu）TOC-V CPH型分析仪，搭配TNM-1总氮模块及ASI-V自动进样器；2023年3月9日后更换为岛津（Shimadzu）TOC-L CPH/CPN型分析仪，搭配TNM-L ROHS总氮模块及ASI-L自动进样器。因两台仪器存在检测差异，本分析仅采用2023年3月9日后的DOC/NPOC检测数据。
阴离子（Cl⁻、NO₃⁻、SO₄²⁻）采用离子色谱系统（ion chromatography system，赛默飞世尔Dionex ICS1100、ICS1000型分析仪搭配AS-DV自动进样器）进行检测。本数据集的方法检出限为：阴离子0.02 mg·L⁻¹，NPOC为0.43 mg·L⁻¹。标注为“BDL”的数值表示其低于仪器检出限。对于低于方法或仪器检出限的数值，本研究在计算与分析过程中将其浓度赋值为定量限的一半。若后续使用本数据集，需对低于方法检出限的数值进行适当筛选处理。标注为“NA”的数值表示未开展检测分析。
2024年8月13日至14日的基流时段内，本研究使用两台Sontek Flowtracker2声学多普勒流速仪（Acoustic Doppler Velocimeters）采集流量数据。流量值采用Flowtracker的断面中部法计算，在河道宽度方向约20个监测点位测定水深与流速。流量的百分比不确定度亦由Flowtracker仪器自动计算得出。为计算比流量，本研究将各监测点位的实测流量按对应贡献流域面积进行归一化处理。

本数据集支撑以下已发表论文：
Weidner, C. R., Zarnetske, J. P., Kendall, A. D., Martin, S. L., Nesheim, S., & Shogren, A. J. (2025). 《湿地、地下水与季节变化对低起伏流域河流水化学空间分布的影响》。《地球物理学研究杂志：生物地球科学》（Journal of Geophysical Research: Biogeosciences），130卷，e2025JG008989。https://doi.org/10.1029/2025JG008989

【摘要】河流水化学格局的解析可为流域生态系统与水文过程研究提供关键认知。在高起伏流域中，溶质运移路径与地表地形高度契合，因此流域溶质的空间分布格局及其控制因子已得到充分研究。然而，在低起伏流域中，水文地质非均质性及河道廊道特征（如湿地）可能影响水体与溶质运移，目前对该类流域溶质格局的控制因子认知仍较为匮乏。本研究针对一处以湿地为主的低起伏流域，基于28个监测点位、历时32个月的58次同步观测，构建了溶质格局数据集，旨在明确流域内主要的地表、地下控制因子及湿地的影响作用。在该低起伏流域中，湿地对溶质的储存、转化与运移的预期效应仅在最小子流域的溶质格局中得以体现；而主河道的大量地下水补给，可能掩盖下游区域的季节变化与湿地对河流水化学的影响。本研究结果表明，在低起伏流域的流域尺度研究中，需纳入动态变化的地下水补给贡献；同时，全面理解湿地对河流水化学的整体影响，需开展多空间与时间尺度的采样工作。因此，在以湿地为主的低起伏流域中，鉴于地表与地下过程共同调控河流水溶质格局，相关模拟研究需同时整合地表与地下水文数据及过程。