Dataset associated with "A First-Order Approximation of Floodplain Soil Organic Carbon Stocks in a River Network: the South Platte River, Colorado, USA"

This data includes floodplain extent, raw floodplain data (elevation, stream order association), floodplain widths, and lake and reservoir information for the South Platte river basin.We use the hydrogeomorphic floodplain tool GFPLAIN to delineate the extent of 100-year floodplains in the South Platte River watershed of Colorado, USA. We distinguish elevation bands for the steppe, montane, subalpine, and alpine zones. We also differentiate bead (floodplain width/channel width > 5) and string (floodplain width/channel width < 5) reaches within the montane and subalpine zones. Drawing on prior, field-based measurements of organic carbon stock in downed, dead wood and soil in these floodplain types, we estimate total floodplain organic carbon storage, which includes organic carbon storage in lake and reservoir sediments in the watershed. Soil constitutes the greatest reservoir of floodplain carbon. The total estimated area of floodplain is 2916 km2, which is 4.3% of the total watershed area of the South Platte River. Our preferred estimate is 42.7 Tg C storage (likely range of 39.1-42.7 Tg). This equates to 11.1% of a previously estimated overall carbon stock (above and belowground biomass and soil organic carbon) in the entire watershed of 384 Tg C. Floodplains are thus disproportionately important, relative to their surface area, in storing organic carbon in this semiarid watershed. Field measurements of floodplain soil organic carbon storage from across the globe indicate that this finding is not unique to this watershed and this has implications for prioritizing floodplain management and restoration as a means of enhancing carbon sequestration

Dataset associated with “Aufeis as a Major Forcing Mechanism for Channel Avulsion and Implications of Warming Climate”

The dataset is a comma separated values (CSV) file that contains the basic data used in analyses (river name, reach number, latitude and longitude of each measurement site, drainage area in km2 at each measurement site, and indication of presence/absence of persistent aufeis accumulation).Prompted by field observation of an aufeis-induced channel avulsion along the Hula Hula River in June 2021, we use measurements of channel migration zone width along 15 rivers flowing north across the Arctic coastal plain in Alaska, USA. We differentiated sites with aufeis that covered > 1 km2 in early summer during the period 2017-2021 from sites without such aufeis formation. All but 4 of the 28 sites with aufeis have widths greater than the 95% confidence interval and 20 sites fall outside of the 95% prediction interval for channel width based on drainage area. Pairwise comparison indicates that the population of aufeis sites have significantly wider channel migration zones (p < 0.0001) than non-aufeis sites after accounting for drainage area. Seasonal aufeis facilitates lateral channel migration and associated heterogeneity. Loss of aufeis under warming climate may reduce habitat diversity in these river corridors

Flow Resistance Dynamics in Step-pool Stream Channels: 1. Large Woody Debris and Controls on Total Resistance

Flow resistance dynamics in step-pool channels were investigated through physical modeling using a laboratory flume. Variables contributing to flow resistance in step-pool channels were manipulated in order to measure the effects of various large woody debris (LWD) configurations, steps, grains, discharge, and slope on total flow resistance. This entailed nearly 400 flume runs, organized into a series of factorial experiments. Factorial analyses of variance indicated significant two-way and three-way interaction effects between steps, grains, and LWD, illustrating the complexity of flow resistance in these channels. Interactions between steps and LWD resulted in substantially greater flow resistance for steps with LWD than for steps lacking LWD. LWD position contributed to these interactions, whereby LWD pieces located near the lip of steps, analogous to step-forming debris in natural channels, increased the effective height of steps and created substantially higher flow resistance than pieces located farther upstream on step treads. Step geometry and LWD density and orientation also had highly significant effects on flow resistance. Flow resistance dynamics and the resistance effect of bed roughness configurations were strongly discharge-dependent; discharge had both highly significant main effects on resistance and highly significant interactions with all other variables

Wood dynamics in headwater streams of the Colorado Rocky Mountains

Peer reviewedPublisher PD

Flow Resistance Dynamics in Step-pool Channels: 2. Partitioning Between Grain, Spill, and Woody Debris Resistance

In step-pool stream channels, flow resistance is created primarily by bed sediments, spill over step-pool bed forms, and large woody debris (LWD). In order to measure resistance partitioning between grains, steps, and LWD in step-pool channels we completed laboratory flume runs in which total resistance was measured with and without grains and steps, with various LWD configurations, and at multiple slopes and discharges. Tests of additive approaches to resistance partitioning found that partitioning estimates are highly sensitive to the order in which components are calculated and that such approaches inflate the values of difficult-to-measure components that are calculated by subtraction from measured components. This effect is especially significant where interactions between roughness features create synergistic increases in resistance such that total resistance measured for combinations of resistance components greatly exceeds the sum of those components measured separately. LWD contributes large proportions of total resistance by creating form drag on individual pieces and by increasing the spill resistance effect of steps. The combined effect of LWD and spill over steps was found to dominate total resistance, whereas grain roughness on step treads was a small component of total resistance. The relative contributions of grain, spill, and woody debris resistance were strongly influenced by discharge and to a lesser extent by LWD density. Grain resistance values based on published formulas and debris resistance values calculated using a cylinder drag approach typically underestimated analogous flume-derived values, further illustrating sources of error in partitioning methods and the importance of accounting for interaction effects between resistance components

Field-based Learning in Surface and Groundwater Processes: Preparing Water Literate Citizens and Water Resource Professionals

Hydrologic field stations installed in the Cache La Poudre River basin will provide authentic field-based learning opportunities for non-majors and majors at Colorado State University to prepare a water literate citizenry and water resource professionals. Previous experience from a campus well field has demonstrated the effectiveness of local field-based instruction in water resources. Results from three semesters of perception surveys and pre- and post-knowledge tests show increased student satisfaction and knowledge gain in fundamental water concepts through the groundwater field exercise. The new hydrologic stations are designed to build upon these results to further improve undergraduate teaching and learning of water concepts in Warner College of Natural Resources (WCNR) using the Poudre watershed as the focus. Given the numerous relevant scientific and societal issues related to our hometown watershed, now is the time to develop high-impact watershed-based learning tools for undergraduates. The hydrologic field stations will span a gradient along the Poudre River and its tributaries from the mountains at CSU’s Pingree Park campus to the plains, providing a full spectrum of geologic, climatic, biologic, and land use characteristics in the watershed. The mid-canyon site at Gateway Natural Area will be the first location accessed either in the field, virtually, or both, by 1300 students in twelve courses in WCNR. Students will collect and analyze the water quantity and quality data that are relevant to the future use of the Cache La Poudre River watershed, and all student-collected data will be made available on the FLOW (Fostering Learning of Water) website. Key learning goals include mastering surface and groundwater flow measurement, flow calculation and interpretation, hydrologic and geomorphic mapping and spatial analysis, assessing physical-biotic interactions along riparian corridors, evaluating human impacts to river networks, assessing alluvial aquifer properties, and computer modeling, thus giving students the broad knowledge and scientific skills necessary to participate as water literate citizens, enter the environmental science workforce, or pursue graduate research

Hydraulics, Morphology, and Energy Dissipation in an Alpine Step-pool Channel

To investigate the relationship between hydraulics and channel morphology in step‐pool channels, we combined three‐dimensional velocity measurements with an acoustic Doppler velocimeter and topographic surveys in a steep step‐pool channel, the Rio Cordon, Italy. Measurements were organized around step, pool, and tread units and occurred within a range of 36%–57% of bankfull discharges. As flow moved from steps to their downstream pools in our study reach, an average of approximately two thirds of the total energy was dissipated, as measured by relative head loss through step‐pool sequences. Much of this head loss was achieved by elevation (potential energy) loss rather than velocity reductions. Although an overall, expected pattern of flow acceleration toward step crests and deceleration in pools was present, pool velocities were high, especially where upstream step crests were irregular and where residual pool depths were low. Many steps were porous or “leaky,” with irregular cross‐channel bed and water surface topography, producing high‐velocity jets and less flow resistance than channel‐spanning dammed steps. Longitudinal variations in hydraulics are thus often overshadowed by lateral variations arising from morphologic complexities. Velocity and turbulence characteristics in the Rio Cordon show marked differences from data we have collected in a more stable and wood‐rich channel in the Colorado Rockies, in which “ponded” steps are more prevalent and pools are slower and more turbulent. Comparison of these channels illustrates that step‐pool structure and hydraulics are strongly influenced by flow regime, sediment supply, lithology, time since the last step‐forming flood, and availability of in‐stream wood

Wood-Based Carbon Storage in the Mackenzie River Delta: The World\u27s Largest Mapped Riverine Wood Deposit

The Mackenzie River Delta (MRD) has been recognized as an important host of river-derived wood deposits, and Mackenzie River wood has been found across the Arctic Ocean. Nevertheless, we lack estimates of the amount of carbon stored as wood and its age in the delta, representing a gap in carbon cycle estimates. Here, we use very high-resolution satellite imagery and deep learning to map wood deposits in the MRD, combining this with field data to measure the stock and age of wood-based carbon. We find \u3e400,000 individual large wood deposits, collectively storing 3.1 × 1012 g-C, equating to 2 × 106 g-C ha−1 across the delta. Sampled wood pieces date from 690 AD to 2015 AD but are mostly young with ∼40% of the wood samples formed after 1955 AD. These estimates represent a minimum bound on an important surficial, potentially reactive, carbon pool compared to other deeper carbon stocks in permafrost zones

Data Associated with "Logjam Characteristics as Drivers of Transient Storage in Headwater Streams"

This repository contains data for the experimental flume and numerical model runs referenced in Marshall et al., 2022. Source code, data csv files for statistical analysis, and calculated temporal moments are included.Logjams in a stream create backwater conditions and locally force water to flow through the streambed, creating zones of transient storage within the surface and subsurface of a stream. We investigate the relative importance of logjam distribution density, logjam permeability, and discharge on transient storage in a simplified experimental channel. We use physical flume experiments in which we inject a salt tracer, monitor fluid conductivity breakthrough curves in surface water, and use breakthrough-curve skew to characterize transient storage. We then develop numerical models in HydroGeoSphere to reveal flow paths through the subsurface (or hyporheic zone) that contribute to some of the longest transient-storage timescales. In both the flume and numerical model, we observe an increase in backwater and hyporheic exchange at logjams. Observed complexities in transient storage behavior may depend largely on surface water flow in the backwater zone. As expected, multiple successive logjams provide more pervasive hyporheic exchange by distributing the head drop at each jam, leading to distributed but shallow flow paths. Decreasing the permeability of a logjam or increasing the discharge both facilitate more surface water storage and elevate the surface water level upstream of a logjam, thus increasing hyporheic exchange. Multiple logjams with low permeability result in the greatest magnitude of transient storage, suggesting that this configuration maximizes solute retention in backwater zones, while hyporheic exchange rates also increase. Understanding how logjam characteristics affect solute transport through both the channel and hyporheic zone has important management implications for rivers in forested, or historically forested, environments.This research was supported by National Science Foundation Hydrologic Sciences (award 1819068)