Browsing by Author "Ross, Matthew R. V., committee member"
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Item Open Access Conservative solute transport processes and associated transient storage mechanisms: a comparison of streams with contrasting channel morphologies, land use, and land cover(Colorado State University. Libraries, 2021) Emanuelson, Karin, author; Covino, Timothy, advisor; Ross, Matthew R. V., committee member; Morrison, Ryan R., committee memberLand use within a watershed impacts stream channel morphology and hydrology and therefore in-stream solute transport processes. In this study, I selected two stream sites with contrasting channel morphology, land use and land cover: Como Creek, CO, a relatively undisturbed, high-gradient, forested stream with a gravel bed and complex channel morphology and Clear Creek, IA, an incised, low-gradient stream with low-permeability substrate draining an agricultural landscape. At these sites, I performed conservative stream tracer experiments to address the following questions: 1) How does solute transport vary between streams with differing morphologies and watershed land use?, and 2) How does solute transport at each stream site change as a function of discharge? I analyzed in-stream tracer time series data and compared results quantifying solute attenuation in surface and subsurface transient storage zones. I found significant differences in solute transport metrics between sites and significant trends in these metrics with varying discharge conditions at the forested site but not at the agricultural site. In the relatively undisturbed, forested stream there was a broad range of transport mechanisms and evidence of substantial exchange with both surface and hyporheic transient storage. In this forested site, changing discharge conditions activated or deactivated different solute transport mechanisms and greatly impacted advective travel time. Conversely, in a simplified, agricultural stream there was a narrow range of solute transport behavior across flows and predominantly surface transient storage at all measured discharge conditions. These results demonstrate how channel simplification resulting from land use change inhibits available solute transport mechanisms across varying discharge conditions.Item Open Access Constraints on mechanical fuel reduction treatments in USFS Wildfire Crisis Strategy priority landscapes(Colorado State University. Libraries, 2024) Woolsey, George, author; Hoffman, Chad M., advisor; Tinkham, Wade T., advisor; Battaglia, Mike A., committee member; Ross, Matthew R. V., committee memberThe US Forest Service recently launched a Wildfire Crisis Strategy outlining objectives to safeguard communities and other values at risk by substantially increasing the pace and scale of fuel reduction treatment. This analysis quantified layered operational constraints to mechanical fuel reduction treatments including existing vegetation, protected areas, steep slopes, and administrative boundaries in prioritized landscapes. A Google Earth Engine workflow was developed to analyze the area where mechanical treatment is allowed and operationally feasible under three scenarios representing a range of management alternatives under current standards. Results suggest that a business-as-usual approach to mechanical fuel reduction is unlikely in most landscapes to achieve the 20-40% of high-risk area treatment objective using mechanical methods alone. Increased monetary spending to overcome physical constraints to mechanical treatment (e.g., steep slopes and road access) opens sufficient acreage to meet treatment objectives in 18 of 21 priority landscapes. Achieving treatment objectives in the remaining landscapes will require both increased spending and navigating administrative complexities within reserved land allocations to implement fuels treatments at the pace and scale needed to moderate fire risk to communities. Broadening the land base available for treatment allows for flexibility to develop treatment plans that optimize across the multiple-dimensions of effective landscape-scale fuel treatment design. Spatial identification of the constraints to mechanical operability allows managers and policymakers to effectively prioritize mechanical and managed fire treatments.Item Open Access Metals export to streams during base flow and storm events in the 416 Fire, southwest Colorado(Colorado State University. Libraries, 2021) Pulver, Bryce A., author; Kampf, Stephanie K., advisor; Ross, Matthew R. V., committee member; Leisz, Stephen J., committee memberWith approximately two thirds of the Western U.S. relying on fresh water from forested areas, it is vital to understand how wildfires can affect the release of metals into soil water and streams. Moderate to high intensity fires can alter the physical and chemical properties of soil, allowing elevated release of sediment, organic matter, and nutrients to streams. While many studies have focused on how fires affect sediment loading, nutrient export, and organic matter; less research has been conducted on how wildfire impacts the export of metals. This study examines metals export from the 2018 416 fire near Durango, CO during baseflow and storm events. Six tributaries (3.88-38.8 km2) and five sites on Hermosa Creek (152-435 km2) were sampled and analyzed for metal concentrations. We examine how metal concentrations relate to burn severity and watershed characteristics under different flow conditions using both univariate correlation analysis and multivariate models. Metal concentrations were significantly greater in burned baseflow samples compared to unburned locations for As, Ca, K, Mg, Mo, Si, Sr, and Zn. Concentrations of As in baseflow exceeded the Environmental Protection Agency's (EPA's) primary drinking water maximum contaminant level (MCL). Metal concentrations in baseflow were positively correlated with percentage of watershed burned, burn severity, and basin slope, and negatively correlated with basin elevation, drainage area, and average annual precipitation. Metal concentrations increased significantly (mean factor change = 20.6) in storm samples compared to pre-storm samples for Al, As, Ba, Ca, Cr, Fe, K, Li, Mg, Mn, Si, and Zn with Al, As, Ba, Be, Cd, Cr, Fe, Mn, Ni, and Pb being above an EPA or World Health Organization (WHO) MCL. Although storm samples were limited, metal concentrations were correlated with watershed burn severity (r ~ 0.8), indicating elevated metal concentrations likely came from burned areas. Overall, this study demonstrated that wildfires cause elevated metal concentrations in both baseflow and stormflow, but with the exception of As, only the stormflow metal concentrations posed water quality concerns, with 10 metals exceeding both EPA and WHO MCL's for drinking water.