Data associated with Elliott et al. Geochemical and sediment dynamics during an experimental high flow pulse event on the Allegheny River: Lessons for river system management

High flow and flood events are important components of natural river flow regimes, as they maintain healthy aquatic habitats and riparian ecosystems. However, human alteration of rivers for flood control, including dam construction, modifies and homogenizes downstream hydrological patterns by moderating extreme high and low flows. In this study, we evaluate the biogeochemical fluxes stemming from the first experimental spring flood (i.e., pulse event) on the Allegheny River (Pennsylvania, USA) conducted by the United States Army Corps of Engineers as part of the Sustainable Rivers Project. The pulse event was initiated on March 30, 2023, by a sustained release of 451 cms from the Kinzua Dam for 21 hours. We hypothesized that this experimental spring pulse would initially lead to the release of organic-rich sediment and nutrients stored behind the Kinzua Dam. We also expected the \"geochemical fingerprint\" of downstream water to change over the duration of the pulse event due to the released flood water interacting with hyporheic water, scouring the channel and riparian areas, and then ultimately receding. To quantify the impact of the pulse on downstream biogeochemistry, we collected hourly water grab samples over a 48-hour period that spanned pre- and post-pulse conditions from multiple locations downstream of the Kinzua Dam. We evaluated the water chemistry of grab samples for multiple parameters, including concentrations of dissolved metals, nutrients, total suspended solids, and nitrate isotopes. Our results indicate that variable water chemistries can be linked to the timing and flushing of different portions of the river channel and floodplain across the span of the pulse event. These results demonstrate the value of downstream monitoring during pulse events for tracing flow dynamics, quantifying material fluxes, and documenting the impact of similar experimental spring floods on downstream river ecosystems. This resource includes the data files of: environmental measurements (including but not limited to water temperature, pH, conductivity); hourly grab sample concentrations of dissolved metals, nutrients, total suspended solids, and nitrate isotopes; United States Geological Survey gage streamflow during the pulse event; and code associated with organizing data and calculations.高流量与洪水事件是天然河流径流情势（river flow regimes）的重要组成部分，它们维系着健康的水生栖息地与河岸生态系统。然而，人类为防洪开展的河流改造活动（包括大坝建设）通过调节极端高、低流量，改变并均质化了下游水文格局。 本研究针对美国陆军工程兵团（United States Army Corps of Engineers）作为可持续河流项目（Sustainable Rivers Project）一部分，在美国宾夕法尼亚州阿勒格尼河（Allegheny River）上开展的首次春季实验性洪水（即脉冲事件），对其产生的生物地球化学通量（biogeochemical fluxes）进行评估。该脉冲事件于2023年3月30日启动，通过金祖阿大坝（Kinzua Dam）持续21小时以451立方米每秒的流量下泄水量。 我们提出假说：此次春季实验性脉冲洪水将率先释放存储于金祖阿大坝后方的富含有机质的沉积物与营养物质。我们同时预期，在脉冲事件持续期间，下泄洪水与潜流带水（hyporheic water）相互作用、冲刷河道与河岸区域并最终退去的过程中，下游水体的"地球化学指纹（geochemical fingerprint）"将发生变化。 为量化此次脉冲洪水对下游生物地球化学过程的影响，我们在覆盖脉冲前后时段的48小时内，于金祖阿大坝下游多个点位采集了每小时一次的瞬时水样（water grab samples）。我们对瞬时水样的多项水质参数进行了分析，包括溶解态金属、营养物质、总悬浮固体以及硝酸盐同位素的浓度。 研究结果表明，在脉冲事件全过程中，水体化学性质的变化可与河道与漫滩不同区域的冲刷时机及冲刷过程相关联。上述结果证实了在脉冲事件期间开展下游监测的价值，可用于追踪径流动态、量化物质通量，并阐明类似春季实验性洪水对下游河流生态系统的影响。 本数据集包含以下数据文件：环境监测数据（包括但不限于水温、pH值、电导率）；溶解态金属、营养物质、总悬浮固体及硝酸盐同位素的每小时瞬时水样浓度数据；脉冲事件期间美国地质调查局（United States Geological Survey, USGS）监测的河道流量数据；以及用于数据整理与计算的配套代码。