Theses and Dissertations at Montana State University (MSU)
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Item Daily signals in nitrate processing provide a holistic perspective on stream corridor hydrologic and biogeochemical function(Montana State University - Bozeman, College of Agriculture, 2023) Foster, Madison Jo; Chairperson, Graduate Committee: Robert A. Payn; This is a manuscript style paper that includes co-authored chapters.Understanding interactive pathways of biogeochemical reaction and water movement in stream corridors is critical given the role stream corridors play in mitigating nitrate loading from agricultural watersheds. However, few studies consider the interactive effects of nitrate loading, riparian processing, and stream ecosystem processing, which may limit abilities to predict downstream nitrate delivery. Riparian groundwater inputs and stream ecosystem processing may vary due to daily cycles in evapotranspiration or stream ecosystem primary production. Recent advances in high-frequency monitoring of stream chemistry throughout the day exhibit potential to explore both hydrologic and biogeochemical influences on nitrate attenuation. In this thesis, I explore how diel variations in stream reach nitrate processing can provide holistic perspectives on the attenuation of nitrate along stream corridors within a watershed that is heavily influenced by agricultural land use. Nitrate processing is defined as the evident changes in nitrate concentration in parcels of water as they travel along a given reach of a stream, as measured from nitrate sensors located at the head and base of ca. 0.5 km reaches. To understand controls on diel variation in nitrate processing, we measured diel processing signals in agricultural headwater reaches in Central Montana, USA spanning variable atmospheric and flow conditions from March through August in 2020-2022. Across 168 days with valid data, most signals exhibited little diel variation (n = 106) and this lack of variation occurred most frequently during cooler and shorter days. In contrast, signals with greater variation were common during longer days, warmer temperatures, and lower flows (n = 62). This seasonal shift in patterns suggests that solar radiation and stream flow are primary controls on diel nitrate processing signals in these low-order reaches. In addition to diel variation, less overall nitrate attenuation in the study reach with direct inputs of high-nitrate upland waters suggest that the degree of hydrologic connection to upland aquifers influences apparent reach nitrate processing. This work highlights how understanding the drivers of diel processing signals may lead to a more holistic understanding of how multiple interacting processes in stream corridors influence nitrate delivery to downstream ecosystems.Item SR and U isotopes reveal interactions of surface water and groundwater along the mountain headwaters to intermountain basin transition (Hyalite Canyon and Gallatin Valley, MT)(Montana State University - Bozeman, College of Agriculture, 2018) Miller, Florence Rita; Chairperson, Graduate Committee: Stephanie A. Ewing; Stephanie A. Ewing, Robert A. Payn, James B. Paces, Sam Leuthold and Stephan Custer were co-authors of the article, 'SR and U isotopes reveal the influence of lithologic structure on stream-groundwater interaction along a mountain headwater catchment (Hyalite Canyon, MT)' submitted to the journal 'Water resources research' which is contained within this thesis.; Stephanie A. Ewing, Robert Payn, Sam Leuthold, Stephan Custer, Tom Michalek and James B. Paces were co-authors of the article, 'SR and U isotopes reveal mixing patterns of groundwater and surface water influenced by human management in an intermountain basin (Gallatin Valley, MT)' submitted to the journal 'Journal of hydrology' which is contained within this thesis.Mountainous regions of the western United States are characterized by steep, rapidly eroding mountain headwater streams transitioning to more depositional intermountain basins. The character and flux of water across these process domains is subject to projected changes in mountain headwater snowpack and agricultural and urban land use in rapidly developing intermountain basins. Here we evaluate controls on water/rock, water/substrate, and surface/groundwater interactions within Hyalite Creek and the Gallatin Valley of southwest Montana. We use solute loads and geochemical tracers (87 Sr/86 Sr, Ca/Sr, and [234U/238U]) as indicators of such interactions. Surface water, groundwater, and soil samples were collected between 2016 and 2018. Stream water in upper Hyalite Creek had low 87 Sr/86 Sr values typical of volcanic and sedimentary host rock units, and low [234 U/238 U] values consistent with shorter flow path soil, shallow aquifer or runoff water. Middle Hyalite Creek had increased [234 U/238 U] values, reflecting groundwater inflows from the Madison Group limestones. Lower Hyalite Creek had an increase in 87 Sr/86 Sr values and decrease in [234 U/238 U] values, indicated contributions from Archean gneiss fracture flow. Using mixing models, we estimate inflows from the Madison contribute ~4% during summer baseflow conditions and inflows from the Archean contribute ~2% to ~8% of streamflow during summer and winter baseflow conditions. At the mountain front, diverse Ca/Sr, 87Sr/86Sr, and [234U/238U] ratios were observed as a result of convergent flow in mountain headwaters catchments. In the intermountain basin, divergent flow at the mountain front recharges valley aquifers and combines with infiltration through soils. With distance down-valley, we observe intermediate values of Ca/Sr, 87 Sr/86 Sr, and [234 U/238 U], suggesting mixing of diverse source waters. Higher concentrations of Sr, alkalinity, and Ca/Sr and 87 Sr/86 Sr ratios consistent with soil carbonates suggest water infiltration through soil facilitated the influence of soil secondary carbonates on groundwater geochemistry. Additionally, increased water movement through soil facilitates the increase in anthropogenic loading of NO3- and Cl- in surface and groundwaters. Our results provide novel quantification of groundwater contribution to streamflow in mountain headwaters, and elucidate water quality and quantity controls from the mountain front across the intermountain basin, including valley aquifer recharge, infiltration through soils, and anthropogenic solute influxes to groundwater.Item Hydrology of a waste rock repository capping system at the Zortman Mine(Montana State University - Bozeman, College of Agriculture, 1997) Warnemuende, E. A.Item Assessing vegetation patterns and hydrologic characteristics of a semi-arid environment using a geographic information system and terrain based models(Montana State University - Bozeman, College of Agriculture, 1993) Jersey, Janelle Kay; Co-chairs, Graduate Committee: Jeffrey S. Jacobsen and John P. WilsonItem Hydrologic-carbon cycle linkages in a subalpine catchment(Montana State University - Bozeman, College of Agriculture, 2008) Riveros-Iregui, Diego Andres; Chairperson, Graduate Committee: Brian L. McGlynn.The feedbacks between the water and the carbon cycles are of critical importance to global carbon balances. Forests and forest soils in northern latitudes are important carbon pools because of their potential as sinks for atmospheric carbon. However there are significant unknowns related to the effects of hydrologic variability, mountainous terrain, and landscape heterogeneity in controlling soil carbon dioxide (CO 2) efflux. Mountainous terrain imposes large spatial heterogeneity in the biophysical controls of soil CO 2 production and efflux, including soil temperature, soil water content, vegetation, substrate, and soil physical properties. Strong spatial and temporal variability in biophysical controls can lead to large heterogeneity in the magnitude of soil CO 2 efflux. This dissertation research investigates the relationships between these biophysical controls and the resultant CO 2 efflux across the soil-atmosphere interface in a 393-ha subalpine catchment of the Northern Rocky Mountains. This study incorporates knowledge gained through field observations (2 growing seasons) at multiple locations distributed across the watershed, and a range of empirical analytical techniques including a modeling approach to estimate point to catchment scale soil CO 2 efflux. Variability in soil CO 2 efflux was strongly related to topography and landscape structure. Riparian meadows were found to have the highest rates of cumulative soil CO 2 efflux across the entire watershed, likely due to more accumulation of soil water than upland sites, leading to enhanced plant and microbial respiration in riparian meadows. Landscape context and appreciation of organized heterogeneity are critical to estimation and interpretation of watershed-scale rates of soil CO 2 efflux and for up-scaling plot or point measurements of soil CO 2 efflux to larger spatial scales. This dissertation provides examples and suggestions for corroboration and integration of soil and canopy level CO 2 fluxes and for process understanding of spatiotemporal variability of biogeochemical processes driven by the hydrologic cycle.Item Hydrology and landscape structure control subalpine catchment carbon export(Montana State University - Bozeman, College of Agriculture, 2009) Pacific, Vincent Jerald; Chairperson, Graduate Committee: Brian L. McGlynn.Carbon export from high elevation ecosystems is a critical component of the global carbon cycle. Ecosystems in northern latitudes have become the focus of much research due to their potential as large sinks of carbon in the atmosphere. However, there exists limited understanding of the controls of carbon export from complex mountain catchments due to strong spatial and temporal hydrologic variability, and large heterogeneity in landscape structure. The research presented in this dissertation investigates the control of hydrology and landscape structure and position on two major avenues of carbon loss from mountain watersheds: soil respiration and stream dissolved organic carbon (DOC) export. Measurements of soil respiration and its biophysical controls (soil water content, soil temperature, vegetation, soil organic matter, and soil physical properties) and stream and groundwater DOC dynamics are presented across three years and multiple riparian-hillslope transitions within a complex subalpine catchment in the northern Rocky Mountains, Montana. Variability in soil respiration was related to hydrologic dynamics through space and time and was strongly influenced by topography and landscape structure. Cumulative soil CO 2 efflux was significantly higher from wet riparian landscape positions compared to drier hillslope locations. Changes in hydrologic regimes (e.g. snowmelt and precipitation timing and magnitude) also impacted soil respiration. From a wet to a dry growing season, there were contrasting and disproportionate changes in cumulative growing season surface CO 2 efflux at wet and dry landscape positions. Stream DOC export was also influenced by landscape structure and hydrologic variability. The mobilization and delivery mechanisms of DOC from the soil to the stream were dependent upon the size of DOC source areas and the degree of hydrologic connectivity between the stream and the riparian and hillslope zones, which varied strongly across the landscape. This dissertation provides fundamental insight into the controls of hydrology and landscape structure on carbon export from complex mountain watersheds. The results of this research have large implications for the carbon source/sink status of high elevation mountain ecosystems, the influence of changing hydrologic regimes on soil respiration, and the use of landscape analysis to determine the locations of large source areas for carbon export.Item The role of stream network nutrient uptake kinetics and groundwater exchange in modifying the timing, magnitude, and form of watershed export(Montana State University - Bozeman, College of Agriculture, 2012) Covino, Timothy Patrick; Chairperson, Graduate Committee: Brian L. McGlynn.; Brian L. McGlynn and Rebecca A. McNamara were co-authors of the article, 'Tracer additions for spiraling curve characterization (TASCC): quantifying stream nutrient uptake kinetics from ambient to saturation' in the journal 'Limnology and oceanography: methods' which is contained within this thesis.; Brian McGlynn and Rebecca McNamara were co-authors of the article, 'Land use / land cover and scale influences on in-stream nitrogen uptake kinetics' in the journal 'Journal of geophysical research - biogeosciences' which is contained within this thesis.; Brian McGlynn and John Mallard were co-authors of the article, 'Stream-groundwater exchange and hydrologic turnover at the network scale' in the journal 'Water resources research' which is contained within this thesis.; Brian McGlynn and Michelle Baker were co-authors of the article, 'Separating physical and biological nutrient retention and quantifying uptake kinetics from ambient to saturation in successive mountain stream reaches' in the journal 'Journal of geophysical research - biogeosciences' which is contained within this thesis.In this PhD dissertation research we sought to elucidate stream network biological and physical influences on hydrological and biogeochemical signatures observed along stream networks and at watershed outlets. Our research indicates that stream nutrient uptake and groundwater exchange processes can modify inputs from terrestrial sources and influence the timing and signature of watershed fluxes. We determined that stream nutrient uptake followed Michaelis-Menten kinetics across a broad range of systems and that land use / land cover change can alter stream nutrient uptake magnitudes. Additionally, we found that watershed structure and network geometry exerted strong controls over sourcewater contributions and streamwater compositions along stream networks and at watershed outlets. Combined, this PhD research suggests that uptake kinetics and hydrologic turnover exert strong controls over streamwater composition and sourcewater contributions, and that physical and biological contributions to total nutrient retention and the dynamic and concentration dependent nature of biological uptake combine to control solute and nutrient signatures. We suggest accurate assessment of total retention across stream reaches and stream networks requires quantification of physical retention and the concentration dependent nature of biological uptake, understanding necessary to help mitigate the potentially deleterious influences elevated nutrient export can have on downstream ecosystems.Item A review of landscape influences on riparian zone processes in mountainous headwater catchments(Montana State University - Bozeman, College of Agriculture, 2012) Stoy, Padraic Fitzgerald; Chairperson, Graduate Committee: Lucy Marshall.Understanding the drivers of riparian zone hydrology is crucial for informed management of water quality, especially in headwater catchments. This study reviews landscape influences on riparian zone processes in mountainous headwater catchments, and combines recent findings and management techniques into a conceptual analysis of riparian zone hydrology and nutrient export. A case study synthesizing recently published work in Tenderfoot Creek Experimental Forest (TCEF) is developed outlining riparian zone hydrology, riparian buffering, and nutrient export. We demonstrate that a major influence on the hydrology and nutrient export in mountainous catchments can be landscape structure, and use this finding as a framework to develop a conceptual approach to riparian zones in mountainous areas. The conceptual analysis is intended to inform management through the identification of riparian areas that are important for stream water quality depending on hydrologic drivers in the catchment. Understanding the variability of riparian zone hydrology and subsequent water quality impacts will allow for more focused and informed management decisions for riparian areas.Item Spatial and seasonal variability of watershed response to anthropogenic nitrogen loading in a mountainous watershed(Montana State University - Bozeman, College of Agriculture, 2010) Gardner, Kristin Kiara; Chairperson, Graduate Committee: Brian L. McGlynn.; Brian L. McGlynn was a co-author of the article, 'Seasonality in spatial variability and influence of land use/land cover and watershed characteristics on streamwater nitrogen export in a developing watershed in the Rocky Mountain West ' in the journal 'Water resources research' which is contained within this thesis.; Brian L. McGlynn was a co-author of the article, 'A multi-analysis approach to assess the spatio-temporal patterns of watershed response to localized inputs of nitrogen' in the journal 'Water resources research' which is contained within this thesis.; Brian L. McGlynn, and Lucy A. Marshall were co-authors of the article, 'Quantifying watershed sensitivity to spatially variable nitrogen loading and the relative importance of nitrogen retention mechanisms' in the journal 'Water resources research' which is contained within this thesis.Anthropogenic activity has greatly increased watershed export of bioavailable nitrogen. Escalating levels of bioavailable nitrogen can deteriorate aquatic ecosystems by promoting nuisance algae growth, depleting dissolved oxygen levels, altering biotic communities, and expediting eutrophication. Despite these potential detrimental impacts, there is notable lack of understanding of the linkages between anthropogenic nitrogen inputs and the spatial and seasonal heterogeneity of stream network concentrations and watershed nitrogen export. This dissertation research seeks to more accurately define these linkages by investigating the roles of landscape position and spatial distribution of anthropogenic nitrogen inputs on the magnitude and speciation of watershed nitrogen export and retention and how these roles vary seasonally across contrasting landscapes in a 212 km ² mountainous watershed in southwest Montana. Results indicate localized inputs of anthropogenic nitrogen occurring in watershed areas with quick transport times to streams had disproportionate effects on watershed nitrogen export compared to spatially distributed or localized inputs of nitrogen to areas with longer transport times. In lower elevation alluvial streams, these effects varied seasonally and were most evident during the dormant winter season by amplified nitrate peaks, elevated dissolved organic nitrogen:dissolved organic nitrogen (DIN:DON) ratios and lower dissolved organic carbon (DOC):total dissolved nitrogen (DOC:TDN). During the summer growing season, biologic uptake of nitrogen masked anthropogenic influences on watershed nitrogen export; however, endmember mixing analysis of nitrate isotopes revealed significant anthropogenic influence during the growing season, despite low nitrate concentrations and DIN:DON ratios. In contrast, streams draining alpine environments consisting of poorly developed, shallow soils and small riparian areas exhibited yearlong elevated nitrate concentrations compared to other sites, suggesting these areas were highly nitrogen enriched. Watershed modeling revealed the majority of watershed nitrogen retention occurred in the upland environment, most likely from biological uptake or lack of hydrologic connectivity. This work has critical implications for watershed management, which include: 1) developing flexible strategies that address varying landscape characteristics and nitrogen loading patterns across a watershed, 2) avoiding clustering nitrogen loading in areas with quick travel times to surface waters, 3) seasonal monitoring to accurately gauge watershed nitrogen saturation status, and 4) incorporating spatial relationships into streamwater nitrogen models.Item Stream-groundwater interactions in a mountain to valley transition : impacts on watershed hydrologic response and stream water chemistry(Montana State University - Bozeman, College of Agriculture, 2005) Covino, Timothy Patrick; Chairperson, Graduate Committee: Brian L. McGlynn.As mountain headwater catchments increase in size to the meso-scale, they incorporate new landscape elements including mountain-valley transition zones. Mountain-valley transition zones form part of the mountain front, influence groundwater (GW)-stream interactions, and impact hydrologic response and stream water composition. Mountain front recharge (MFR) in mountain-valley transition zones and subsequent GW discharge to streams in the valley bottom are important hydrological processes. These GW-stream interactions are dynamic in both space and time, playing a key role in regulating the amount, timing, and chemistry of stream water reaching the valley bottom. I hypothesize that mountain-valley transitions function as hydrologic and biogeochemical buffers via GW recharge and subsequent GW discharge. More specifically, that streams often recharge GW near the mountain front and receive stored GW further downstream. To investigate these processes I applied physical hydrology techniques, and geochemical hydrograph separations in the Humphrey Creek watershed in southwestern Montana. This allowed me to assess the spatial and temporal variability of mountain front GW recharge and GW-stream interactions across a mountain-valley transition. Geochemical signatures were used to partition stream flow into alpine runoff and GW sources. These results indicate that much of the alpine stream water recharged GW at the mountain front and that stored GW of a different chemical composition sustained down-valley stream discharge. Down-valley stream discharge was dominated by GW inputs and responded to GW stage more closely than upstream reaches. A critical GW stage height was necessary for down-valley channel flow, as this was the only major input to channel flow during early and late season base flow. Conversely, GW contributed little to stream flow in the upper reaches of the study area. GW-stream water exchange served as a flow and geochemical buffer, resulting in significant changes in stream chemistry from the alpine, to the MFR zone, to the valley bottom and muting fluctuations in channel flow, both at high and low flow. Implications are that mountain front GW recharge magnitudes can control valley aquifer storage state which combined with alpine runoff magnitude and valley bottom GW discharge controls stream water quantity and geochemical composition downstream.