Repository logo

Browsing by Author "Morrison, Ryan R., advisor"

Now showing 1 - 3 of 3
  • Thumbnail Image
    ItemUnknown
    Decreasing stream habitat for Greenback cutthroat trout under future climate projections in headwater streams of the southern Rocky Mountains, Colorado
    (Colorado State University. Libraries, 2022) Ma, Chenchen, author; Morrison, Ryan R., advisor; Nelson, Peter, committee member; Kanno, Yoichiro, committee member
    Headwaters are vital to the abundance and diversity of biota as they produce various temperatures, light, hydrologic regimes, water chemistry, substrate type, food resources, and species pools. Many studies have shown that headwater streams are especially vulnerable to changing climate, and coldwater fish are especially sensitive to the fluctuations in streamflow and water temperature during summertime low flows. Though previous studies have provided insights on how changes in climate and alterations in stream discharge may affect the habitat requirements for native cutthroat trout species, the suitable physical habitats have not been evaluated under future climate projections for the threatened Greenback Cutthroat Trout (GBCT) occupying the headwater regions in the Southern Rocky Mountains. Thus, this study used field data collected in the summers of 2019 and 2020 from selected headwater streams across the Front Range in the Southern Rocky Mountains to construct one-dimensional hydraulic models (HEC-RAS) to evaluate streamflow and physical habitat under four future climate projections. A principal component analysis (PCA) was then performed to demonstrate the importance of each morphological feature of these streams. Results illustrate high variations in both predicted streamflow reductions and physical habitat for all future climate projections. The projected mean summer streamflow shows much greater decline compared to the projected mean August flow. Moreover, sites located at higher elevations with larger substrate (D50 and D84) and steeper slopes may experience greater reductions in physical habitat under mean summer future climate projections. Future climate change studies on cold-water fisheries need to take multiple influential factors into account instead of heavily focusing on the thermal characteristics. Reintroduction and management efforts for GBCT should be tailored to the individual headwater stream with adequate on-site monitoring that can be applied in a more holistic manner as well.
  • Thumbnail Image
    ItemOpen Access
    Evaluating surface water–groundwater interactions in floodplains using SWAT+ and gwflow
    (Colorado State University. Libraries, 2023) Schulz, Evan, author; Morrison, Ryan R., advisor; Bailey, Ryan T., advisor; Wohl, Ellen, committee member
    Floodplains are essential ecosystems that provide a variety of economic, hydrologic, and ecologic services. Within floodplains, surface water-groundwater exchange plays an important role in facilitating biogeochemical processing and can have a strong influence on hydrology through infiltration or discharge of water. These functions can be difficult to assess due to the heterogeneity of floodplains and monitoring constraints, so numerical models are useful tools to estimate fluxes, especially at a large scale. In this study, the gwflow module of the SWAT+ (Soil and Water Assessment Tool) ecohydrological model quantified magnitudes and spatiotemporal patterns of floodplain surface water-groundwater exchange in a mountainous watershed using an updated version of the module that directly calculated floodplain-aquifer interactions during periods of floodplain inundation. The gwflow module is a spatially distributed groundwater modeling subroutine within the SWAT+ code that uses a gridded network and physically based equations to calculate groundwater storage, groundwater head, and groundwater fluxes. I used SWAT+ to model an area of 7,516 km2 in the Colorado Headwaters HUC8 watershed (14010001) and used streamflow data from USGS gages in the watershed for calibration and testing. I evaluated model performance for scenarios with and without simulated floodplain-groundwater exchange and for three gwflow grid cell sizes. Models that included floodplain-groundwater interactions outperformed those without such interactions and provided valuable information about floodplain inundation and exchange rates. Furthermore, I found that smaller gwflow cell sizes showed similar or better performance than larger cell sizes and simulated additional information about local variations in groundwater fluxes, especially within floodplains. Finally, my analyses on the location of floodplain fluxes in the watershed showed that wider areas of floodplains, "beads," exchanged a higher net and per area volume of water, as well as higher rates of exchange, than narrower areas, "strings." These outputs remained consistent across all studied cell sizes, with smaller cells simulating greater differences between bead and string floodplain regions. Study results show that floodplain surface water-groundwater exchange is a valuable process to include in hydrologic models, and model outputs could inform land conservation practices by indicating priority locations where substantial hydrologic exchange occurs.
  • Thumbnail Image
    ItemOpen Access
    Multiscale connections between a groundwater dependent ecosystem and socio-hydrology: insight gained from numerical modeling, geospatial informatics, and Bayesian statistics
    (Colorado State University. Libraries, 2023) Lurtz, Matthew R., author; Morrison, Ryan R., advisor; Bhaskar, Aditi S., committee member; Bailey, Ryan T., committee member; Ross, Matthew, committee member
    The connectivity between floodplain practices and groundwater dependent ecosystems (GDE) is undeniable, yet difficult to measure. Quantifying the connection between ecosystems would be ideal for the conjunctive management of groundwater and surface water resources in an irrigated river valley. In the research presented, a variety of methodologies are used to understand the socio-hydrologic connections between a semi-arid GDE and agro-pastoral practices in southeastern Colorado (USA). I investigated the socio-hydrologic relationships between a GDE and the surrounding floodplain using three approaches. First, I used the output from a calibrated groundwater model and a remote sensing evapotranspiration (ET) algorithm with exploratory statistics. Second, I used remotely sensed vegetation information and socio-hydrologic data in a Bayesian hierarchical time series and spatial statistics models to compliment the first approach by examining new explanatory covariates. Third, a simple regression framework examines the point-scale relationship between groundwater and ET to further dissect results from the first approach at a finer resolution. These three approaches yielded key results. From the first objective, the dual-model comparison agreed with previous ecological research showing a non-linear relationship between ET and groundwater depth (0-5 m), and a threshold was identified at three meters where the rate between ET and groundwater depth change. The time series and spatial statistics objective helped identify a spatial scale threshold to detect temporal trend, lagged intra-seasonal predictors of vegetation water use, and which floodplain characteristics impact vegetation density. This statistical analysis discovered that temporal trend is not detectable at spatial scales larger than catchment size (> 10 km). Monthly temperature and lagged monthly values of precipitation and stream gain-loss (i.e., an return flow indicator variable) are all predictive of temporal changes in riparian vegetation density. Based on the floodplain characteristics tested in the spatial statistics approach, perennial tributaries to the Arkansas River increase vegetation density while the conversion of agriculture to fallow land decrease riparian vegetation density. The third objective highlighted that the process between evapotranspiration and groundwater head is non-linear but depends on temporal scale and plant functional group. The results from these approaches is important for GDE preservation in the face of increasing demand on groundwater supply. The process between groundwater and ET is of particular importance in large scale water balance studies that include a groundwater and surface water interface with need to model the groundwater-ET relationship in natural and agricultural ecosystems simultaneously.