2022

Monitoring the Recovery of the Coal Creek Ecosystem Following the Marshall Fire

Anonymous — Wed, 06 Apr 2022 21:27:20 +0000

Monitoring the Recovery of the Coal Creek Ecosystem Following the Marshall Fire Anonymous (not verified) Wed, 04/06/2022 - 15:27 Lane Allen , Lauren Magliozzi

The December 30th, 2021 Marshall Fire was the most property destructive fire in babyֱ��app’s history. The Marshall Fire burn extent overlaps much of the Coal Creek drainage area, including protected habitat for sensitive species in Open Space areas and a 14-mile recreational pathway between Superior and Erie. Fires at the wildland-urban interface (WUI) pose a serious risk to the health of stream ecosystems and the safety of nearby recreation. Wildfires are known to increase nutrient concentrations in streams that can adversely impact stream health and can cause harmful algal blooms. Fires that occur in WUI areas, such as the Marshall Fire, also pose unique environmental toxicity risk due to the combustion of household materials and industrial constituents that contain toxic metals (e.g., zinc, lead, copper), which can have a toxic impact on stream biota such as periphyton and benthic invertebrates. This study analyzes standard water quality parameters, metals concentration, and benthic invertebrate and periphyton health in the immediate aftermath of the Marshall Fire along Coal Creek in Superior, Louisville, and unincorporated Boulder County.

lauren.magliozzi@colorado.edu (contact)

Civil, Environmental, and Architectural Engineering Graduate Students, CU Boulder

Lane Allen and Lauren Magliozzi

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Exploring ice’s role in river bank migration through permafrost

Anonymous — Wed, 06 Apr 2022 21:26:27 +0000

Exploring ice’s role in river bank migration through permafrost Anonymous (not verified) Wed, 04/06/2022 - 15:26 Josie Arcuri

Icy river dynamics set the rate of material exchange between arctic channels and their floodplains. As they migrate across arctic landscapes, icy rivers limit the residence time of soil organic carbon (SOC) by transferring some river bank material to the fluvial network before it can completely decompose. In this way, bank migration limits SOC oxidation in a deepening permafrost active layer and modulates the landscape-wide carbon budget. Concurrently, arctic river banks are laden with permafrost ice wedges and channels themselves are occupied by ice for a significant portion of the hydrograph; these factors are known to affect fluvial potential to erode and remove material from floodplains. However, we do not know how ice impacts rates of river bank migration through permafrost, especially in small arctic watersheds like the Canning Rivers on Alaska's North Slope. We aim to quantify how much SOC the Canning River removes from its floodplain over a typical year by differencing satellite-collected images. Based on initial results, the Canning seems to migrate much less than expected over the last two decades. We will use similar remote sensing methods - in addition to planned field sampling - to identify the annual cycles of river ice occurrence and bank ice content on the Canning. Ice observations will be compared to locations of actual and expected river bank migration. Expected river bank migration will be predicted from classical river bank migration models based on rivers with no ice content in their banks or channels. We hypothesize that models of bank migration based on non permafrost rivers over predict fluvial erosion into permafrost banks, and that river ice occurrence and bank ice content will correlate with that overprediction. We can also make use of this work in predicting the future contribution of the Canning river, and other arctic landscapes, to the global carbon budget. This work has immediate importance for people who traverse or depend on arctic landscapes, but especially those who live within them. Arctic landscape response to climate change is just as much a story about the loss of place and vanishing resources as it is about a dynamic earth system.

Josephine.Arcuri@colorado.edu

Geology Graduate Student, CU Boulder

Josie Arcuri

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Water in the Age of the Megafire

Anonymous — Wed, 06 Apr 2022 21:25:16 +0000

Water in the Age of the Megafire Anonymous (not verified) Wed, 04/06/2022 - 15:25 Kate Boden

Wildfires are an increasingly common occurrence in the Western United States. Wildfire mitigation measures – or “forest treatments” –are being utilized to reduce fire severity and protect valuable resources. By reducing forest density, treatments have the potential to reduce evapotranspiration (ET), potentially leaving excess water available for runoff. Past work has verified that large reduction in forest density can increase runoff. However, there is significant debate surrounding moderate reduction in forest density and the impact on runoff. Past results are highly variable, finding increased, reduced, or no change in runoff depending on the study. To improve our understanding this research asks, how do forest treatments impact water yield at the Sagehen Watershed? At what spatial scale is the impact quantifiable? Located in the Sierra Nevada Mountains of California, Sagehen offers a unique and ideal location of study because 1) multiple types of forest treatment were conducted across the watershed, and 2) nine streamflow gauges were distributed throughout the basin to capture spatially localized changes at sub-basin scale. Results show that since 1954, precipitation accounts for 93% of water yield variability and forest treatment starting in 2014 did not alter this. For the past 20 years, ET remained relatively constant especially in the context of highly variable precipitation. Year-to-year changes in basin and sub-basin scale ET never exceeded 15%, while year-to-year changes in precipitation exceeded 100%. Treatments had minimal impact on forest structure, and as far as it relates to the water budget, no impact on water yield was observed at either the basin or sub-basin scale. The largest treatment plan for a sub-basin, 56% of total area, did result in a 15% change in sub-basin ET. However, this decrease in ET did not translate to an observable increase in water yield. Overall, this study helps inform water resource management decisions and natural resource protection measures as we adapt to climate resilient forests and water supplies.

kboden@mines.edu

Graduate Student, babyֱ��app School of Mines

Kate Boden

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Quantifying Dynamic Rock Moisture and its Role in Supporting Transpiration in a Montane Catchment of the babyֱ��app Front Range.

Anonymous — Wed, 06 Apr 2022 21:24:32 +0000

Quantifying Dynamic Rock Moisture and its Role in Supporting Transpiration in a Montane Catchment of the babyֱ��app Front Range. Anonymous (not verified) Wed, 04/06/2022 - 15:24 Ethan Burns

Warming across the western US continues to reduce snowpack, shift melt dates, and increase atmospheric demand, leading to uncertainty about moisture availability in upland forest ecosystems. As many of these forests are characterized by thin or absent soils and extensive rooting into weathered bedrock, deep vadose zone water is thought to be a central determinant in controlling late season water availability and may mitigate water stress during a changing climate. A key impediment to understanding the role of the deep vadose zone as a reservoir, lies in the challenge of quantifying the plant available moisture held here and its relationship to snowmelt and rainfall timing. As a result, few direct measurements of rock moisture exist, and questions remain about what controls moisture availability to plants during the growing season. In this study, we quantify the spatiotemporal dynamics of rock moisture and its role in sustaining transpiration and mitigating drought stress in montane catchment of the babyֱ��app Front Range. We find reductions in dynamic rock moisture during the 2021 growing season are concurrent with drying soil moisture, persistent transpiration, and in some cases reduced water stress. Lower bound estimates of dynamic storage show weathered rock on southern aspects account for at least 9-12% of the mean annual water inputs. These findings provide some of the first direct measurements of rock moisture storage and use in the Rocky Mountains and supports previous work that indicates rock moisture use is not just confined to periods of drought or to Mediterranean and semi-arid climates.

Ethan.Burns@colorado.edu

Geography Graduate Student, CU Boulder

Ethan Burns

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First Users Areas and Climate-Water Coupling in Western US Basins

Anonymous — Wed, 06 Apr 2022 21:23:51 +0000

First Users Areas and Climate-Water Coupling in Western US Basins Anonymous (not verified) Wed, 04/06/2022 - 15:23 Noah Campbell

The relationship between climate and water supply in the American West has been altered by changes in water storage management, water diversion, and agricultural and urban water infrastructure. The strength of coupling between water supply and climate is measurable, should vary with rate of water development in a basin, and will vary geographically from headwaters to downstream. However, most existing literature on coupled climate-watershed systems focuses on either the highest elevation headwaters where water is sourced or the large agricultural and urban centers much further downstream. While management of headwater regions of the western United States determine the strength of coupling between climate and water availability downstream, more attention is needed on how water is managed in between upland source areas and large-scale agricultural and population centers. To this end, I focus on First Users areas, which sit between the highest and lowest parts of a basin. First Users areas are often characterized by lower agricultural capacity and population, a relative lack of political power in water management decisions, distinct land-use patterns (e.g., hay production for use in grazing rather than row crops), proximity to publicly managed lands, and the presence of senior but relatively low quantity water rights. Using a set of physical and social criteria, I delineate western basins into archetypes to develop a preliminary social-environmental model of the First Users areas. I will show a method of evaluation for the strength of coupling with regards to recorded and future projected climate variability and subsequent responses to basins in the American West. Physical and social relationships in western basins are nonlinear and occur in both upstream and downstream directions, and this research will further the understanding of these relationships as water availability changes in the region.

Noah.Campbell@colorado.edu

Geography and Earth Lab Graduate Student, CU Boulder

Noah Campbell

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Resolving Flow-Dependent Geochemical Indicators of Groundwater Exchange in the Columbia River, WA

Anonymous — Wed, 06 Apr 2022 21:23:04 +0000

Resolving Flow-Dependent Geochemical Indicators of Groundwater Exchange in the Columbia River, WA Anonymous (not verified) Wed, 04/06/2022 - 15:23 Margaret DiGiorno

Surface water-groundwater exchange in streams is influenced by hydrologic conditions in the aquifer, hydraulic conditions in the channel, and the spatial distribution of permeability under and around the channel. The exchange with adjacent aquifers is less well understood in large rivers because tracer experiments are much more difficult due to water depth and higher flows than in small streams where they have been used. In this study we ask whether groundwater discharge along a 75 km reach of the Columbia River near the Hanford Site in eastern Washington is determined more by the large scale geologic units in the area or by finer scale riverbed interface sediment deposits. In 2021 we collected water quality data in February (~146 kcfs) and July (~117 kcfs). In July we also collected river bed geophysical data using a floating transient electromagnetic system (FloaTEM). We classified water quality anomalies by depth, temperature, and electrical conductivity (EC). Anomalies (though not always the same type) were identified at many of the same locations in February and July. The majority of the anomalies (69% in February and 52% in July) were high EC and high temperature compared to the river. High temperature inflows with a similar EC to river water were identified in July, but not in February. Though high temperature summer anomalies were unexpected, we found that the average temperature in wells in the area in July (about 22 C) was higher than the river temperature (about 20 C). Preliminary analysis of the geophysical data suggests that areas with high resistivity (which indicates more permeable sand and coarse-grained material) aligned with water quality anomalies – water quality anomalies not aligned with resistivity shifts are likely associated with surface controls (such as irrigation return flows).

Margaret.Digiorno@colorado.edu

Civil, Environmental and Architectural Engineering Graduate Student, CU Boulder

Margaret DiGiorno

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Rivers and Rocks: A New Model for River Profile Evolution with Heterogeneous Substrate and Bedload Transport

Anonymous — Wed, 06 Apr 2022 21:22:24 +0000

Rivers and Rocks: A New Model for River Profile Evolution with Heterogeneous Substrate and Bedload Transport Anonymous (not verified) Wed, 04/06/2022 - 15:22 Vanessa Gabel

Variation in bedrock erodibility along a river profile gives rise to differences in vertical incision rate and influences sediment characteristics such as clast lithology, coarse sediment generation rate, and grain size. In rivers whose beds are eroded, in part, through sediment abrasion, these streamwise sediment dynamics are part of a crucial feedback that sets the dominant fluvial erosion process and determines whether a river exhibits transport-limited or detachment-limited behavior. The role that sediment plays in setting the shape of a river profile is of particular interest in the case of a river’s transient response to external forcing. Here we present a model that explores river profile evolution in a setting with streamwise bedrock variability. Our model combines theory for five interrelated processes: bedload sediment transport in equilibrium gravel-bed channels, channel width adjustment to flow and sediment characteristics, abrasion of bedrock by mobile sediment, plucking of bedrock, and progressive loss of gravel-sized sediment due to grain abrasion. We envision a generic “range-foreland” system that consists of erosion-resistant, crystalline rocks in the upstream reaches, juxtaposed with softer, more erodible rocks downstream. In this setting, coarse sediment generation is confined to the upstream part of the fluvial system. As the sediment is transported downstream, it creates an alluvial blanket across the soft, fine-grained unit. Bedrock erosion is modulated by the thickness of the alluvial layer. We use the model to explore the range of transient forms that can occur in such a setting in response to changes in tectonic or climatic regime. We pay special attention to the conditions under which the upstream gravel source either increases the downstream fluvial gradient (by partially shielding the underlying material from incision) or decreases the gradient (by providing tools that amplify the efficiency of abrasion). We also examine the conditions under which erosion is concentrated at the downstream-most reaches of the river profile, versus at the lithologic boundary. While our work takes its motivation from the Southern Rocky Mountains and High Plains of North America, the model is applicable generally to settings in which a bedrock-incising river traverses multiple lithologies. This work aims to improve our interpretations of the history of river profiles in lithologically heterogeneous environments and inform our understanding of landscape evolution in these settings.

vanessa.gabel@colorado.edu

Geolology Graduate Student, CU Boulder

Vanessa Gabel

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Modeling satellite-based Antarctic melt leads to higher Southern Ocean sea ice extent by 2100

Anonymous — Wed, 06 Apr 2022 21:21:45 +0000

Modeling satellite-based Antarctic melt leads to higher Southern Ocean sea ice extent by 2100 Anonymous (not verified) Wed, 04/06/2022 - 15:21 Tessa Gorte

In this work, we leverage data from the Gravity Recovery and Climate Experiment (GRACE) satellite to force the Community Earth System Model version 2 (CESM2), a global climate model, to explore the impacts of freshwater discharge from the Antarctic Ice Sheet (AIS) on Southern Ocean and global ocean dynamics. As the planet warms, the AIS is rapidly losing mass. Most of this mass loss is concentrated in a region referred to as the West Antarctic Ice Sheet (WAIS). This AIS mass loss is typically not well represented in global climate models as many models do not have an active ice sheet component meaning that the AIS doesn't interact with the land, ocean, atmosphere, or sea ice regimes. To mimic AIS mass loss, we use data from the GRACE satellite, which measures changes to the Earth's gravity field, to create a freshwater forcing that we then input directly into the ocean component of CESM2. Running the model out to 2100 under Shared Sociobabyֱ��app Pathway 5-8.5, we compare output from our satellite-based freshwater forcing simulation to a control simulation with the same parameterizations but constant freshwater forcing. We find that the addition of freshwater into the Southern Ocean results in higher Southern Hemisphere sea ice extent, relatively cooler sea surface temperatures, and a relatively stronger Atlantic Meridional Overturning Circulation by the end of the 21st century.

tessa.gorte@colorado.edu
Atmospheric and Oceanic Sciences Graduate Student, CU Boulder

Tessa Gorte

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Examining Spatial Differences in Soil Solute Chemistry in a Semi-arid Montane Catchment, Manitou Experimental Forest, babyֱ��app

Anonymous — Wed, 06 Apr 2022 21:21:10 +0000

Examining Spatial Differences in Soil Solute Chemistry in a Semi-arid Montane Catchment, Manitou Experimental Forest, babyֱ��app Anonymous (not verified) Wed, 04/06/2022 - 15:21 Reece Gregory

Biogeochemical properties of soils play a crucial role in soil and stream chemistry throughout a watershed. How water interacts with soils during subsurface flow can have impacts on water quality, thus, it is crucial to understand where and how certain soil water chemical processes occur within a catchment. In this study, ~200 soil samples were evaluated throughout a small catchment in Manitou Experimental Forest to examine spatial and vertical patterns in major soil solutes among different landscape units: riparian areas, alluvial fans, and steep hillslopes. Solutes were extracted from the soil samples in the laboratory and analyzed for major cations (Li, K, Mg, Br, and Ca) and anion (Fl, Cl, NO2, NO3, PO4, and SO4) concentrations using ion chromatography. Concentrations of most solutes were greater in near surface soils (10cm) than in deeper soils (100cm) across all landscape units, except for fluoride which was found to increase with depth. Potassium was found to have the highest variation between depths, with the largest range of 1.039mg/l (100cm) to 3.127mg/l (10cm) being in riparian areas. Nearly every solute was found to be enriched in riparian areas, with mean concentrations being higher than the hillslopes and fans, NO3 being the only notable exception with concentrations greater in the alluvial fans. Br, NO2, and PO4 concentrations were often below the detectable limit, and Li and Na were not variable between depths or landscape units. Overall, based on the comparisons between depths and landscape units, findings suggest that K, Mg, Ca, Fl, and NO3 solutes may serve as valuable tracers to identify subsurface flowpaths from different landscape units and depth within this catchment.

Reece.Gregory@babyֱ��app.EDU

Geography Undergraduate Student, CU Boulder

Reece Gregory

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Streamflow Resulting from Forest Disturbance

Anonymous — Wed, 06 Apr 2022 21:20:20 +0000

Streamflow Resulting from Forest Disturbance Anonymous (not verified) Wed, 04/06/2022 - 15:20 Thomas Heydman

The Western United States is dominated by snow water hydrology systems in forest catchments. Climate change is causing forest disturbances to increase in severity and occur more frequently. The consequences of these disturbances impact the ecology of these systems as well as the timing and quantity of streamflow from snowmelt and runoff. I examined the headwaters of the Rio Grande (RGHW), a snow water dominated system, which has suffered tree mortality as a result of multiple that occurred in 2013, as well as beetle kill dating back to the late 1990s. Using geospatial data collected on beetle kill severity and fire data, I quantified the percentage mortality by area. I then compared this to available streamflow and SNOTEL data to determine the effect of disturbance history on streamflow. Using annual streamflow and SNOTEL data as an input/output ratio, I concluded that years 2015 & 2016 had a higher than historical ratio of streamflow (output) for precipitation (input) received by the RGHW. The most likely mechanism causing the increased runoff ratio can be attributed to the increased hydrophobicity of the soil, as well as a decrease in transpiration rates due to tree mortality. Despite these changes in hydrology, the watershed returns to the historic range within just a few years as the soil recovers and revegetation leads to an increased demand for water. The results of my study have larger implications for water forecasting in the west, which continues to suffer from larger, more frequent disturbances, as well as a growing population and an increasing daily average temperatures resulting from climate change.

theydman@colostate.edu

College of Natural Resources Undergraduate Student, babyֱ��app State University

T.R. Heydman

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