Theses and Dissertations

Permanent URI for this collection

https://hdl.handle.net/10217/100404

Browse

Now showing 1 - 20 of 68

Open Access
Motorized winter recreation impacts on snowpack properties
(Colorado State University. Libraries, 2011) Heath, Jared Tucker, author; Fassnacht, Steven, advisor; Elder, Kelly, committee member; Stednick, John, committee member; Wilson, Kenneth, committee member
Winter recreation, consisting of snowshoeing, skiing, snowboarding, and snowmobiling, has been increasing annually in Colorado's forests. This increase in recreational activity creates direct and indirect wildlife interactions. Motorized winter recreation in the backcountry compacts the snow possibly influencing the physical and mechanical properties of the snowpack. Snow depth, density, stratigraphy and grain characteristics control to the insulating properties of the snowpack and create habitat for small non-hibernating mammals. Changes to these physical properties and compaction of the subnivean space may be detrimental to these species. Two hypotheses were formulated: (1) a snowpack compacted by motorized winter recreation will result in changes to physical and mechanical properties of the snowpack; and (2) the amount of motorized winter recreation and the depth of snow when motorized winter recreation begins affects the physical properties of the snowpack. During the 2009-2010 winter season snow compaction plots near Rabbit Ears Pass and Fraser Experimental Forest, Colorado were manipulated with varying use of motorized winter recreation (low, medium and heavy use) beginning on different snow depths, shallow (30 cm) and deep (120 cm). Physical and mechanical properties of the snowpack, including snow density, temperature, snow depth, snow water equivalent, stratigraphy, hardness and ram resistance were measured and used to examine the statistical difference between no use and varying degrees of motorized winter recreation (low, medium and heavy use). The results were used to infer implications on changes to the insulative value of the subnivean space and the potential for movement by subnivean mammals. The largest differences in snowpack properties were associated with motorized winter recreation beginning on a shallow snowpack. Compaction from motorized winter recreation that began on a shallow snowpack increased both mean and subnivean density, hardness, and ram resistance, which resulted in significant differences (p<0.10) between varying use of motorized winter recreation and no use. Snow depth and basal temperatures (ground/snow interface) decreased as a result of motorized winter recreation beginning on a shallow snowpack (p<0.10), while temperature gradients were unaffected throughout the duration of the winter season. Implications to changes in these snowpack properties could decrease the insulative value of the snowpack and make movement by small mammals that utilize the subnivean space more difficult. On the contrary, motorized winter recreation that began on a deep snowpack showed no significant difference suggesting later initiation of use minimizes changes to snowpack properties from compaction.
Open Access
Comparison of digital terrain and field-based channel derivation methods in a subalpine catchment, Front Range, Colorado
(Colorado State University. Libraries, 2012) Hastings, Blaine, author; Kampf, Stephanie, advisor; Laituri, Melinda, committee member; Niemann, Jeffrey, committee member
Understanding the reliability of digitally derived channel networks for mountainous headwater catchments is important to many water resource and land-use management applications. Digital elevation models (DEMs) have become an essential tool for an increasing array of mountain runoff analyses. The purpose of this study is to investigate the influence of digitally-derived topographic variables on channel network formation for a high-elevation glaciated watershed. To accomplish this, our objectives were to (1) test how differences in gridded DEM resolution affect spatially distributed topographic parameters of local slope (tan β), specific contributing area (αs), and topographic wetness index (TWI) derived from both eight and infinite directional flow algorithms, (2) map the actual stream channel network at Loch Vale and examine the influence of surface variables on channel initiation, and (3) evaluate the performance of common methods for deriving channel networks from gridded topographic data by comparing to the observed network. We found that coarser DEM resolution leads to a loss of detail in spatial patterns of topographic parameters and an increase in the calculated mean values of ln(αs) and TWI. Grid cell sizes above 1m result in a substantial shift in the overall cumulative frequency distributions of ln(αs) and TWI towards higher values. A field survey at Loch Vale revealed a complex and disjointed channel network, with 242 channelized points and 30 channel heads. We found no predictable relationships between channel head locations and geomorphic process domains. Analysis of variance (ANOVA) showed no statistically significant difference in mean ln(αs) and TWI for channel head locations grouped by elevation, aspect, slope, formation process or upslope land cover type. For most DEM resolutions and flow partitioning algorithms, deriving channel networks with spatially constant flow accumulation and TWI thresholds provides poor network representation. The publicly available National Hydrography Dataset (NHD) layer oversimplifies the channel network by neglecting almost all first and second order channels. Many of the DEM-derived channel networks that use spatially constant flow accumulation and TWI thresholds also do not reproduce the locations of low order channels in the observed channel network well. Assumptions of topographic control on channel initiation are not shown to be valid at Loch Vale, likely due to their inability to capture subsurface processes and geologic features important to channel formation. However, if using these topographically dependent threshold methods to delineate channel networks, we suggest the use of field-based survey data to identify appropriate thresholds. With appropriate thresholds, both 1m and 10m DEMs can produce channel networks with similar drainage densities to the observed network, even if locations of low order channels are not predicted accurately. Performance degrades for 30m DEMs, so we suggest that DEMs with resolutions coarser than 10m should be avoided for channel network delineation.
Open Access
Evaluating the spatial variability of snowpack properties across a northern Colorado basin
(Colorado State University. Libraries, 2012) Sexstone, Graham Andrew, author; Fassnacht, Steven, advisor; Laituri, Melinda, committee member; Sibold, Jason, committee member
Knowledge of seasonal mountain snowpack distribution and estimates of its snow water equivalent (SWE) can provide insight for water resources forecasting and earth system process understanding, thus, it is important to improve our ability to describe the spatial variability of SWE at the basin scale. The objectives of this thesis are to: (1) develop a reliable method of estimating SWE from snow depth for the Cache la Poudre basin, and (2) characterize the spatial variability of SWE at the basin scale within the Cache la Poudre basin. A combination of field and Natural Resource Conservation Service (NRCS) operational-based snow measurements were used in this study. Historic (1936 - 2010) snow course data were obtained for the study area to evaluate snow density. A multiple linear regression model (based on the historical snow course data) for estimating snow density across the study area was developed to estimate SWE directly from snow depth measurements. To investigate the spatial variability and observable patterns of SWE at the basin scale, snow surveys were completed on or about April 1, 2011 and 2012 and combined with NRCS operational measurements. Bivariate relations and multiple linear regression models were developed to understand the relation of SWE with physiographic variables derived using a geographic information system (GIS). SWE was interpolated across the Cache la Poudre basin on a pixel by pixel basis using the model equations and masked to observe SCA (from an 8-day MODIS product). The independent variables of snow depth, day of year, elevation, and UTM Easting were used in the model to estimate snow density. Calculation of SWE directly from snow depth measurement using the snow density model has strong statistical performance and model verification suggests the model is transferable to independent data within the bounds of the original dataset. This pathway of estimating SWE directly from snow depth measurement is useful when evaluating snowpack properties at the basin scale, where many time consuming measurements of SWE are often not feasible. Bivariate relations of SWE and snow depth measurements (from WY 2011 and WY 2012) with physiographic variables show that elevation and location (UTM Easting and UTM Northing) are most strongly correlated with SWE and snow depth. Multiple linear regression models developed for WY 2011 and WY 2012 include elevation and location as independent variables and also include others (e.g., eastness, slope, solar radiation, curvature, canopy density) depending on the model dataset. The final interpolated SWE surfaces, masked to observed SCA, generally show similar patterns across space despite differences in the 2011 and 2012 snow years and differing estimation of SWE magnitude between the combined dataset of field-based and operational-based measurements (modelO+F) and the dataset of operational-based measurements only (modelO). Within each of the model surfaces, interpolated volume of SWE was greatest within Elevation Zone 5 (3,043 - 3,405 m). The percentage of the total interpolated SWE volume for each model was distributed similarly among elevation zones.
Open Access
A climatological study of snow covered areas in the western United States
(Colorado State University. Libraries, 2012) Moore, Cara, author; Kampf, Stephanie K., advisor; Fassnacht, Steven R., committee member; Sibold, Jason S., committee member
Snow accumulation and timing of melt affect the availability of water resources for the Western United States. Climate warming can significantly impact the hydrology of this region by decreasing the amount of precipitation falling as snow and altering the timing of snowmelt and associated runoff. Therefore, it is essential to characterize how regional climatology affects snow accumulation and ablation and to identify areas that may be especially sensitive to climate warming. This can help resource managers plan appropriately for hydrologic changes. This study utilizes 11-year average (2000 - 2010) MODIS Snow Cover Area (SCA) and Land Surface Temperature (LST) data and annual PRISM precipitation to determine how elevation, slope orientation, latitude, and continentality influence regional characteristics of SCA and LST for early April, early May, early June, and early July in four focus regions: the Colorado Rockies, the Sierra Nevada, the Washington Cascades, and the Montana Rockies. Then, using monthly averages of the 11-year MODIS SCA for January to June, we examine the spatiotemporal evolution of the snowpack and LST throughout the Western U.S. We use threshold values of January to July 11-year average SCA to determine the duration of snow persistence and delineate zones of intermittent, transitional, persistent and seasonal snow. Within the transitional and persistent snow zones, we use 11-year average LST data for January-February-March (LSTJFM) to categorize five different snow sensitivity zones. Areas with the highest winter average land surface temperatures are assumed to be most sensitive to climate warming, whereas areas with the lowest land surface temperature are assumed to be least sensitive. Results show that snow cover tends to increase with increasing elevation, and the elevation of snow cover is lower in higher latitudes, maritime environments, and most western slopes. Land surface temperature tends to decrease with increasing elevation, increasing latitude, and tends to be colder on most western slope sites. The largest divergence between eastern and western slope SCA and LST characteristics is observed in the Sierra Nevada, while little divergence is observed in the Colorado Rockies. Snow cover in the Western U.S. is observed predominantly along two main axes: from north to south along the Cascades and the Sierra Nevada, and from northwest to southeast along the axis of the Rocky Mountain Cordillera. The snow line is lowest in the Washington Cascades and highest in the Colorado Rockies; between these two areas a northwest/southeast elevation gradient is observed. The warmest snow zones (warmest JFMLST) are at lower elevations of the Cascades/Sierra Nevada and in the southwest, whereas coolest snow zones (coldest JFMLST) are in the interior northern Rockies, mid to higher elevations of the Cascades, and the higher elevations of the Colorado Rockies and the Sierra Nevada. The warmest snow zones are likely to be most sensitive to climate warming, as these locations are vulnerable to shifting toward intermittent winter snow cover.
Open Access
Effects of conjunctive use on streamflow at the Tamarack State Wildlife Area, northeastern Colorado
(Colorado State University. Libraries, 2012) Donnelly, Erin, author; Stednick, John, advisor; Ronayne, Michael, committee member; Sale, Thomas, committee member; Kampf, Stephanie, committee member
The Tamarack Recharge Project in northeastern Colorado is intended to augment the streamflow of the South Platte River by 10,000 acre-feet between April and September to increase aquatic habitat for four federally threatened or endangered bird and fish species in Nebraska. The project goal is to retime surface water flows by pumping unappropriated alluvial groundwater into a recharge pond where it infiltrates and returns to the river at critical low flow periods. Retimed surface water flow will help maintain critical habitat for native aquatic species by increasing streamflow without harming water rights holders. To evaluate the effects of this managed groundwater recharge on streamflow in the South Platte River, the hydrologic environment was characterized and quantified through streamflow monitoring, water table elevation mapping, and a groundwater tracer study. Stream discharge measurements were taken at 4 cross sections on the South Platte River. Two cross sections were considered upgradient of the recharge pond and two were downgradient of the recharge pond. The mean flow of the upstream cross sections was 2.64 cubic meters per second (cms) compared to 2.66 cms at the downstream cross sections, which was not a significant difference. A fluorescein tracer study was used to estimate groundwater travel times and hydraulic conductivity. Based on the arrival time of the breakthrough curve at different piezometers, the mean hydraulic conductivity was estimated to be 331 m/d. Using this value, the estimated return time to the South Platte River at 4 cross sections ranged from 92 to 534 days. Measurements of discharge and water table elevations suggesting that Tamarack Project did not produce a measureable increase in streamflow in the South Platte River during the target period are not indicative of project functionality. The annual volume of water pumped into the recharge pond was less than 1% of the annual yield of the South Platte River. While the volume of return flows did not produce measureable results in the river, data from the tracer study and in-stream vertical hydraulic gradient data indicate a gaining stream condition during the fall and a losing stream during the winter and early spring. Potential source(s) of groundwater discharging to the stream include the recharge pond and irrigation return flows and warrant further study.
Open Access
Practical snow depth sampling around six snow telemetry (SNOTEL) stations in Colorado and Wyoming, United States
(Colorado State University. Libraries, 2012) Kashipazha, Amir, author; Fassnacht, Steven, advisor; Kampf, Stephanie, committee member; Laituri, Melinda, committee member; Arabi, Mazdak, committee member
Across the Western United States, the Natural Resources Conservation Service (NRCS) operates about 700 automated snowpack telemetry (SNOTEL) measurement stations. These stations measure snow depth (SD), snow water equivalent (SWE), air temperature and precipitation. To assess how representative the stations are of the surrounding 1 km2 area, a set of approximately 200 snow depth measurement were taken using ten 1000-m transects sampled at 50-m intervals. This sampling was undertaken at the Dry Lake, Joe Wright, Lizard Head, Niwot, (in Colorado) South Brush Creek, and Togwotee Pass (in Wyoming) SNOTEL stations during the winters of 2008, 2009, and 2010. Various sampling patterns were employed at each sampling point, such as three depth measurements in a row parallel or perpendicular to a transect, and five in a row or five in a plus pattern. We used these patterns and various sub-sets of the 1 km2 surrounding area to assess suitable and practical sampling strategies, to determine the minimum number of transects need for measuring the average SD of each station, to evaluate if each station represent the SD average of its 1 km2 area surrounding, and to investigate inter- and intra-annual variations of SD for each station. Statistical analysis used the least-significant-based analysis of variance with a 95 percent confidence level. Statistical analyses showed snow depth averages of incorporated sampling methods were not significantly difference at the 95 percent confidence level. Therefore, any sampling method could be used for SD measurement based on sampling constraints. We recommend measuring three to five snow depths at each sampling spot and the distance between sampling spots should be less than 200m. The minimum number of transects needed for each station was not the same and it depended upon the physiographic and vegetation heterogeneity of the area surrounding a station. Snow depth varied within a 1 km2 area surrounding of SNOTEL station and we did not find two sampling methods that had the same average SD. However, this did not mean that the average SD using a variety of sampling methods was significantly different at the 95 percent confidence level. A heterogeneous snowpack is caused variations in precipitation, wind patterns, solar radiation, etc. Physiographic and vegetation characteristics can be used as surrogates for these meteorological factors that vary at the small and large scale. The effect of these factors on snowpack heterogeneity is more likely greater when the distance of sampling spots is more than 1 km. The correlation between snowpack heterogeneity and the surrogate characteristics varied in spatially and temporally, and from location to location. The Dry Lake, Joe Wright, Lizard Head, and Niwot SNOTEL stations represented the SD average of their 1 km2 area surrounding while Lizard Head station represented the SD average of its 0.36 km2 area surrounding, all at the 95 percent confidence level. However, the Togwotee Pass and South Brush Creek stations did not represented the SD average of their surrounding area. Whether a SNOTEL station does or does not represent the SD average of its surrounding area is related to the complexity of the terrain. For example, the area surrounding the Joe Wright station has complex terrain but represented the station SD while the South Brush Creek terrain was more homogeneous and did not represent station SD. The performance of the SD sensor at the SNOTEL station can be affected by the interaction of meteorology, physiography, vegetation, and possibly human influences, that can produce an highly varying snow pack under and/or around a SD sensor and led to a lack of sensor representivity or sensor error. Due to potential SD sensor and sampling errors a reasonable amount of error for snow samples, such as 5-10% should be considered.
Open Access
Water quality and survivability of Didymosphenia geminata
(Colorado State University. Libraries, 2012) Beeby, Johannes, author; Stednick, John D., advisor; Fassnacht, Steven R., advisor; Clements, William H., committee member
Didymosphenia geminata or Didymo has become a world-wide invasive aquatic species. During blooms, the algae can form thick mats covering entire reaches of stream bottom, which in turn creates negative aesthetic, ecologic, and economic impacts. Although Didymo is historically present in the United States, it is spreading quickly into areas that were previously free of it, and is even growing in waters that were thought not ideal habitat for Didymo. Previous research on how water quality affects Didymo growth and spreading appear to be influenced by streamflow rates and water pH levels. Other water quality parameters have not been fully tested on Didymo, which would contribute to a better understanding of what controls Didymo growth. The first goal of this study was to colonize Didymo in an artificial stream within a laboratory setting. The second goal was to evaluate the survivability of Didymo by exposing it to different water quality parameters. Artificial stream configurations with various light intensity and duration, water temperature and velocity, source water chemistry, and different growth media were used. In all attempts colonization of Didymo was unsuccessful as Didymo slowly deteriorated and became covered by other algae that were more successful in the artificial conditions. Didymo survivability as affected by a 60 minute exposure to different water quality parameters followed previously determined results in that known algaecides did affect cell viability, while other non-toxic parameters showed no effect on Didymo. Nitrate, nitrite, phosphate, chloride, calcium, and magnesium did not affect Didymo survivability. Ammonia also did not affect Didymo but signs of cells lysis were observed and possible mortality may occur with longer exposure times. Copper, zinc, chlorine, and pH affected Didymo survivability. Copper showed the greatest affect on Didymo survivability with the median lethal concentrations (LC50) for copper at 9.3°C and 13.0°C being 3.3 mg/L and 5.4 mg/L respectively at pH 7.7. For copper toxicity in waters with a lower pH (6.7) the resulting LC50 was 33 mg/L. Generally, both colder water temperature and higher pH increased copper toxicity on Didymo. The affect of temperature on copper toxicity was shown to be statistically significant (p-value 0.02). However, there was no statistically significant affect of pH on copper toxicity (p-value 0.07). The LC50 could also not be determined for all three zinc tests but the highest zinc concentration of 40 mg/L had on average 56% of Didymo cells surviving. No apparent trend on the affect of temperature to zinc toxicity on Didymo could be determined; however, the interaction of temperature on zinc toxicity was statistically significant (p-value 0.02). Chlorine at temperatures of 11.5°C and 17.3°C had LC50s of 5.67 and 8.46 mg/L respectively. The affect of temperature on chlorine toxicity was statistically significant (p-value <0.001). Didymo survivability was affected in water with pH 4.3 but not in water with pH 5.9 and 6.9. Cell lysis was occurring in water with pH 10.7 but no sign of any affect on Didymo survivability was found in water with pH 9.9.
Open Access
Alpine wind speed and blowing snow trend identification and analysis
(Colorado State University. Libraries, 2012) Fuller, Jamie D., author; Laituri, Melinda, advisor; Cooley, Daniel, committee member; Doesken, Nolan, committee member; Elder, Kevin, committee member
The substantial quantity of climate change related analyses has resulted in increased research efforts concerning temporal wind speed trends. A change in wind speeds over time could have a widespread effect on snow transport and distribution in alpine regions. Since alpine meteorological stations are sparsely distributed, the intentions of this research were to explore North American Regional Reanalysis (NARR) to assess long-term trends of atmospheric conditions affecting snow transport with greater spatial coverage. NARR is a consistent, continuous and long-term dataset spanning the extent of North America at a spatial resolution of 32 km2 grids. NARR data were compared to two alpine sites (Niwot Ridge, Colorado and Glacier Lakes Ecological Experiments Station, Wyoming) from1989 to 2009. Multiple analyses were conducted to evaluate dataset agreement and temporal trends of alpine climatic conditions at the annual, seasonal and daily scales. The correlation of temperature, precipitation and wind speed between NARR and alpine in situ datasets showed temperature data as correlated, but wind and precipitation lacked agreement. NARR wind speed data were systematically lower when compared to observational data for both locations, but the frequency of wind events was captured. Thus, to more accurately assess blowing snow dynamics using NARR additional methods would be needed to relate the lower wind speed values to the extent of blowing snow. Trend analyses of wind speed datasets for each temporal scale (annual, seasonal and daily) showed slight trends, minimal significance and trends were not significantly different between NARR and in situ data. The statistical similarities were observed for trends with opposite signatures and slopes and a result of weak trends. Additional blowing snow analyses were conducted using temperature, wind speed and precipitation to estimate probable blowing snow events. The low agreement between NARR and observational data for wind speed and precipitation parameters prohibited the use of NARR to assess blowing snow processes and expand spatial and temporal coverage.
Open Access
Local understanding of hydro-climate changes in Mongolia
(Colorado State University. Libraries, 2012) Sukh, Tumenjargal, author; Fassnacht, Steven, advisor; Laituri, Melinda, committee member; Fernandez-Gimenez, Maria, committee member; Butters, Greg, committee member
Air temperatures have increased more in semi-arid regions than in many other parts of the world. Mongolia has an arid/semi-arid climate where much of the population is dependent upon the limited water resources, especially herders. This paper combines herder observations of changes in water availability in streams and from groundwater with an analysis of climatic and hydrologic change from station data to illustrate the degree of change of Mongolian water resources. We find that herders' local knowledge of hydro-climatic changes is similar to the station based analysis. However, station data are spatially limited, so local knowledge can provide finer scale information on climate and hydrology. We focus on two regions in central Mongolia: the Jinst soum in Bayankhongor aimag in the desert steppe region and the Ikh-Tamir soum in Arkhangai aimag in the mountain steppe. As the temperatures have increased significantly (more in Ikh-Tamir than Jinst), precipitation amounts have decreased in Ikh-Tamir which corresponds to a decrease in streamflow, in particular, the average annual streamflow and the annual peak discharge. At Erdenemandal (Ikh-Tamir) the number of days with precipitation has decreased while at Horiult (Jinst) it has increased. Herders observed that the amount of precipitation has decreased (71% in Jinst; 100% in Ikh-Tamir) in recent years. The long-term average streamflow of the Tuin River at Jinst has not changed significantly while the herders have seen a depletion of water resources (73% of respondents). The Khoid Tamir River at Ikh-Tamir has seen a statistically significant decline in the average annual streamflow and the annual maximum daily discharge, which was also observed by all herders surveyed.
Open Access
Watershed characteristics that are related to the occurrence of impaired (CWA 303(d)) waters for park units within the Pacific West Region of the National Park Service
(Colorado State University. Libraries, 2012) Ling, Jia L., author; Laituri, Melinda, advisor; Loftis, Jim, committee member; Newman, Gregory, committee member
Since the establishment of the Clean Water Act (CWA) in 1972, the federal government has made significant strides toward improving the quality of U.S. water resources. The Total Maximum Daily Load (TMDL) program created from the federal CWA distributed the responsibility for improving water quality to states, territories, and authorized tribes, while appointing the U.S. Environmental Protection Agency (EPA) as the lead oversight. Over 43,500 TMDL plans have been developed according to the EPA's national summary of TMDL information. However, implementation of TMDLs is often delayed, which hinders improvement in water quality and may reduce the restoration potential of an impaired waterbody. The National Park Service (NPS) is an important stakeholder in the TMDL program because restoring and preserving water quality for future uses and enjoyment is a vital component of its mission. Therefore, the goal of this study is to identify watershed characteristics that are relevant to the occurrence of impaired waters within watersheds that intersect park units. This will assist NPS managers in evaluating waterbodies at risk and restoration potential. An initial list of 25 watershed characteristics was identified to be included in this study. A survey was administered to NPS aquatic professionals to further reduce the number of characteristics and evaluate the most pertinent characteristics based on professional opinions. Eleven watershed characteristics were selected and quantified to examine their correlation to the occurrence of impaired waters. Watershed characteristics were chosen to represent each of the three categories: (1) land cover / use, (2) ecological / physical characteristics, and (3) social influences. The study area was limited to HUC 12 polygons that intersect park units within the Pacific West Region of NPS. Watershed characteristics and impairments were measured for all intersecting HUC 12 polygons. Impairments were assessed based on state listings of CWA 303(d) waters and categories 4a, 4b, and 4c of CWA Section 305(b). Linear regression analysis was employed to investigate the correlation between each watershed characteristic to percent impairment. The results of the analyses revealed that average slope, amount of hydrography, agricultural land cover, and forest land cover were significant indicators of impaired waters at alpha 0.10 level. Although many of the watershed characteristics may have synergistic effects, multicollinearity was not considered in the design of this study. However, the results of this study may guide water quality professionals to hone their efforts on actively managing the significant watershed characteristics identified in this study.
Open Access
Using snow telemetry (SNOTEL) data to model streamflow: a case study of three small watersheds in Colorado and Wyoming
(Colorado State University. Libraries, 2013) Deitemeyer, David C., author; Fassnacht, Steven, advisor; Laituri, Melinda, committee member; Arabi, Mazdak, committee member
The use of operational snow measurements in the Western United States is instrumental in the successful forecasting of water supply outlooks. The focus of this study is to determine if hydro-meteorological variables available from Snow Telemetry (SNOTEL) stations could successfully estimate the annual total runoff (Q100) and components of the hydrograph, in particular, the date of the passage of 20% of the Q100 (tQ20), 50% of Q100 (tQ50), 80% of Q100 (tQ80), and the peak runoff (Qpeak). The objectives are to: (1) determine the correlation between streamflow and hydro-meteorological variables (from SNOTEL station data); (2) create a multivariate model to estimate streamflow runoff, peak streamflow, and the timing of three hydrograph components; (3) run calibration/testing on the model; and (4) test the transferability to two other locations, differing in catchment area and location. Snow water equivalent (SWE) data from the Natural Resources Conservation Service (NRCS) Joe Wright Snow Telemetry (SNOTEL) was correlated to streamflow at the United State Geological Survey (USGS) Joe Wright Creek gauging station. This watershed is located between the Rawah and Never Summer Mountains in Northern Colorado and has a drainage area of 8.8 km2. Temperature data were not used due to non-stationarity of this time series, while the SWE data were stationary over the 33-year period of record. From the SNOTEL SWE data, peak SWE, date of peak SWE, and number of consecutive days with snow on the ground up to the date of peak SWE had the strongest correlation to streamflow (R2 = 0.19 to 0.58). A collection of models runs were tested with various SNOTEL variables to develop optimal models for each of the five hydrograph components (tQ20, tQ50, tQ80, Q100, Qpeak). Five of the six estimates of were made at the date of Peak SWE. A refined estimate was made for the Q100 at melt-out, when the SWE equaled zero at the SNOTEL station. For the model development, most of the model trials (78%) had a Nash-Sutcliffe coefficient of efficiency (NSCE) value of greater than 0.50. The variables were analyzed for collinearity through a Variance Inflation Factor (VIF). Models with low collinearity (VIF < 5) and greatest accuracy from the calibration and testing periods were selected as optimal model configurations for each of the hydrograph components. The optimal model configuration in the Joe Wright Creek watershed had strong performance for the tQ20, tQ50, Q100 and Qpeak (NSCE > 0.50). The tQ80 model was the least accurate model (NSCE = 0.32). Applying the optimal model equation to the two larger watersheds; Shell Creek is located in Big Horn Mountains of Northern Wyoming (with a drainage area of 59.8 km2) and Booth Creek is located north of Vail in Central Colorado (with a drainage area of 16.0 km2). Basin specific coefficients were generated for a calibration period (1980 to 1996), and evaluated for a testing period (1997 to 2012). A majority of the model outcomes were considered good, with 72% of the outcomes having NSCE > 0.50. The Q100 at melt-out model performed the best (NSCE = 0.62 to 0.94). In a final analysis, the Joe Wright Creek coefficients were applied directly to the two larger watersheds to test model transferability. The location specific model coefficients did not perform well for the other two basins. However, for the Shell Creek watershed, results were still good for the following variables: tQ20, Q100 (using data up to peak SWE and using all SWE data including melt-out) and Qpeak, with NSCE values of 0.45, 0.46, 0.47, and 0.37, respectively. The similar results between Joe Wright Creek and Shell Creek watersheds suggest comparable physiographic characteristics between the two watersheds. An earlier observed onset of snowmelt (as indicated by tQ20) at the Booth Creek watershed influenced the overall accuracy of the model transferability. Despite the differences in the transferability of the model, the optimal configured models derived from accessible SNOTEL data and basin specific coefficients serve as a beneficial tool to water managers and water users for the forecasting of hydrograph components.
Open Access
Social perceptions versus meteorological observations of snow and winter along the Front Range
(Colorado State University. Libraries, 2013) Milligan, William James, author; Fassnacht, Steven, advisor; DiEnno, Cara, committee member; De Miranda, Michael, committee member
This research aims to increase understanding of Front Range residents' perceptions of snow, winter and hydrologic events. This study also investigates how an individual's characteristics may shape perceptions of winter weather and climate. A survey was administered to determine if perceptions of previous winters align with observed meteorological data. The survey also investigated how individual characteristics influence perceptions of snow and winter weather. The survey was conducted primarily along the Front Range area of the state of Colorado in the United States of America. This is a highly populated semi-arid region that acts as an interface between the agricultural plains to the east that extend to the Mississippi River and the Rocky Mountains to the west. The climate is continental, and while many people recreate in the snowy areas of the mountains, most live where annual snowfall amounts are low. Precipitation, temperature, and wind speed datasets from selected weather stations were analyzed to determine correct survey responses. Survey analysis revealed that perceptions of previous winters do not necessarily align with observed meteorological data. The mean percentage of correct responses to all survey questions was 36.8%. Further analysis revealed that some individual characteristics (e.g. winter recreation, source of winter weather information) did influence correct responses to survey questions.
Open Access
Numerical modeling of streamflow accretion by conjunctive use at Tamarack Ranch State Wildlife Area, Colorado
(Colorado State University. Libraries, 2013) Roudebush, Jason A., author; Stednick, John D., advisor; Ronayne, Michael J., committee member; Fassnacht, Steven R., committee member
Conjunctive use of groundwater at Tamarack Ranch State Wildlife Area is used to augment streamflow in the Platte River during low flow periods, critical for aquatic species. As part of a cooperative Tri-State Agreement (TSA) with Nebraska and Wyoming, Colorado's portion of the TSA is to pump alluvial groundwater (up to 1,233 ha-m) during periods of unappropriated flow in the river, to recharge ponds located in upland eolian sand deposits, where the water infiltrates into the ground and returns to the river at a later time. Understanding the location of these recharge ponds and the timing of streamflow accretion is critical for evaluating the effectiveness of recharge operations at Tamarack but has proven difficult to physically measure. To better understand the streamflow-aquifer system changes, a detailed numerical model was created using the MODFLOW Streamflow-Routing technique to simulate physically based groundwater-surface water interaction from managed groundwater recharge. The simulation modeled groundwater pumping from December 2012 through March 2013 and showed that managed groundwater recharge at Tamarack is producing a quantifiable contribution to streamflow in the desired period of April to September and on the Tamarack property. Streamflow accretion began ten days after the pumps were turned off and the center of mass arrived at the river 16 days later. The total volume of streamflow accretion simulated in this study at the Red Lion Bridge was 878,000 m3, 13% of the 6,887,000 m3 of groundwater pumped into the recharge ponds in water year 2013. Streamflow accretion had not fully diminished by the end of model simulation in August 2013, warranting further study to better account for all streamflow accretions.
Open Access
Effects of mountain pine beetle caused tree mortality on streamflow and streamflow generation mechanisms in Colorado
(Colorado State University. Libraries, 2014) Maggart, Ariann Lenore, author; Stednick, John D., advisor; Fassnacht, Steven, committee member; Ronayne, Michael, committee member
The mountain pine beetle (Dendroctonus ponderosae Hopkins) (MPB), an endemic beetle in Colorado forests, saw dramatic population growth in the 1990's. As a result of this epidemic, the mountain pine beetle killed large tracts of forest as it spread. To evaluate the effects of MPB caused tree mortality on streamflow and streamflow generation mechanisms multiple investigative approaches were taken. In north-central Colorado, 21 watersheds representing minimally to highly affected watershed areas were chosen. Physical watershed characteristics were determined through a geographic information system. Long-term streamflow records for each watershed were assessed for data stationarity and change-points in peak flow, date of peak flow and annual water yield. Peak streamflow, date of peak streamflow and annual water yield all had stationarity. Since data were stationary, change-point analyses were not conducted. Streamflow, groundwater and precipitation samples were collected and analyzed for stable isotope concentrations. Isotopes of 2H and 18O partition source water contributions to streamflow from precipitation as snow or rain and groundwater (as a surrogate for groundwater). Annual δ2H and δ18O isotopic signatures for streamflow and streamflow source waters, as snow, groundwater and rain, were determined and used to partition source water contributions to streamflow for each watershed. In general, during the 2012 water year, source water contributions to streamflow were as follows: snow 60%, groundwater 20% and rain 20%. The correlations between snow, groundwater and rain contributions to streamflow and MPB killed area were not statistically significant at α ≤ 0.05 (psnow = 0.582, pgroundwater = 0.543 and p;rain = 0.897). While Colorado has suffered extensive forest kill since the onset of the MPB epidemic, the results of this study suggest that MPB killed watershed area has little to no effect on peak streamflow, date of peak streamflow, annual water yield or streamflow generation mechanisms.
Open Access
Prediction of selenium in Spring Creek and Fossil Creek, Colorado
(Colorado State University. Libraries, 2014) Pierce, Adam L., author; Stednick, John D., advisor; Boone, Randall B., committee member; Thornton, Christopher I., committee member
The role and importance of selenium as an environmental contaminant has gained widespread attention among research scientists, natural resource managers, and federal and state regulatory agencies during the last two decades. Selenium has been listed on Colorado's Clean Water Act Section 303(d) List of Impaired Waters for Spring Creek and Fossil Creek in the city of Fort Collins. Selenium is one of the most hazardous of the trace metals, following mercury, with a narrow range between dietary deficiency and toxicity. Identifying selenium sources and understanding the environmental processes controlling how selenium is introduced to streams is critical to managing and mitigating the effects of elevated concentrations. A modeling approach was used to predict selenium concentrations with exploratory variables including 15 geospatial landscape parameters, precipitation, and streamflow for 5 sub-watersheds within Spring Creek and Fossil Creek watersheds. A correlation analysis was applied with surface water selenium concentrations and the better exploratory variables identified. Selected variables were used in a multiple linear regression model. Various combinations of different variables determined the best performing model, and included the area of shale, area of moderate to strongly alkaline soils, and the length of streams with an adjusted R2 of 0.99, [Se µg/L = 24.038 + 9.516(ALK) - 0.782(STR) -1.039(SHL)]; where ALK = area (km2) of moderate to strongly alkaline soils; STR = length (km) of streams; SHL = area (km2) of shale. Additional multiple linear regression models were developed in ArcGIS® using Ordinary Least Squares (OLS) Regression, and Geographically Weighted Regression (GWR) with area weighted geospatial variables. The best performing OLS model used only area (km2) of wetlands, with an adjusted R2 of 0.98, [Se µg/L = -6.584 + 170.509(wetlands)]. Similarly, the best performing GWR model included area of wetlands, with an adjusted R2 of 0.98. The second best performing GWR model included area of shale, with an adjusted R2 of 0.66. Limitations of this model include a very small sample size of water quality sampling stations, which limits the statistical power of multiple regression models used. Additional techniques applied in basin delineations with landscape element coupling for identification of hydrologic and/or chemical response units can further develop the platform for future modeling efforts targeting unmonitored watersheds.
Open Access
Post-fire erosion response and recovery, High Park Fire, Colorado
(Colorado State University. Libraries, 2014) Schmeer, Sarah R., author; Kampf, Stephanie, advisor; MacDonald, Lee, committee member; Rathburn, Sara, committee member
Wildfires along the Colorado Front Range are increasing in extent, severity and frequency, and a better understanding of post-fire erosion processes is needed to manage burned lands. The objectives of this study were to: 1) document post-fire sediment production after the 2012 High Park Fire burn area, Colorado, 2) determine how sediment production relates to fire, rainfall, surface cover, soil and topographic characteristics, 3) model sediment yield at the study swales using the RUSLE and ERMiT erosion models and a site-specific multivariate regression (SSMR) model developed from the field measurements, and 4) assess how well the RUSLE and SSRM models performed when using remotely-sensed data in place of field-measured data. Sediment production, rainfall, surface cover, soil and topographic characteristics were measured for 29 swales in the High Park Fire burn area from August 2012 through September 2013. Eight of the swales were mulched with either wood shreds in October 2012 or straw in June 2013. Mean sediment yield from the unmulched swales in 2012 was 0.5 Mg ha-1 yr-1, increasing to 14.3 Mg ha-1 yr-1 in 2013. The increase in 2013 was largely due to above-average rainfall amounts. Mulched swales yielded 3.1 Mg ha-1 yr-1 in 2013. Precipitation thresholds for sediment production were best identified by rainfall erosivity. The erosivity threshold in 2012 was 3 MJ mm ha-1 hr-1 increasing to 22 MJ mm ha-1 hr-1 in 2013. Annual total sediment yield in 2013 was most closely correlated with rainfall erosivity whereas 2013 event sediment yield was more closely related by the thirty-minute maximum rainfall intensity. Independent variables with the strongest significant correlations to sediment yield were surface cover and topographic characteristics. Sediment yield was positively correlated with exposed bare soil in 2012 (Pearson's correlation coefficient [r] = 0.56) and negatively correlated with vegetation cover in 2013 (r = -0.46). Sediment yield was negatively correlated with percent cover by mulch (r = -0.97), but the type of mulch material did not affect sediment yield. Slope length was negatively correlated with sediment yield (r = -0.19), and narrower swales produced more sediment per unit area than wide swales. The best 2013 annual SSMR model used average percent bare soil in spring 2013, swale width-length ratio, summer erosivity, slope length and burn severity to predict sediment yield (R2 = 0.63). The two erosion models, ERMiT and RUSLE, did not accurately predict 2013 annual sediment yields. ERMiT under-predicted sediment yields for storms with maximum thirty-minute intensity recurrence intervals of 1.5-5 years, and over-predicted sediment yield for storms with precipitation depth recurrence intervals of 30-100 years. The RUSLE model run with field-measured independent variables similarly did not accurately predict sediment yield from the hillslopes (R2 = 0.05), and when the RUSLE variables were calculated with remotely sensed or GIS-derived data the correlation with measured values was even weaker (R2 = 0.02). The SSMR model developed from field-measured variables predicted sediment yield relatively well (R2 = 0.63), but declined when using remotely-derived data (R2 = 0.46). The results of this study show that rainfall erosivity and intensity, surface cover and topography are the dominant controls on post-fire sediment yield. The interactions of these controls is not captured in the existing erosion models ERMiT and RUSLE. Furthermore, the use of remote sensing and GIS to derive model inputs reduces the accuracy of these models.
Open Access
Exploration of a geometric approach for estimating snow surface roughness
(Colorado State University. Libraries, 2015) Kamin, David Jeffrey, author; Fassnacht, Steven R., advisor; Stednick, John D., committee member; Bauerle, William, committee member
The roughness of a surface that influences atmospheric turbulence is estimated as the aerodynamic roughness length (Z0), and is used to understand the flow of air, temperature, and moisture over a surface. Z0 is a critical variable for estimating latent and sensible fluxes at the surface, but most land surface models treat Z0 simply as a function of land cover and do not address the variability of this value, such as due to changing snow surfaces. This is due in large part to the difficulty and cost of obtaining reliable estimates of Z0 under field conditions. This work addresses the need for versatile methods to evaluate snow surface roughness on a plot-scale. This study used anemometric data from a meteorological tower near Fort Collins, Colorado over two winters (2013-2014). Thorough screening yielded 153 wind-speed profiles which were used to calculate the aerodynamic roughness length at different times and under different snow conditions. The anemometric Z0 values observed in this study with changing surface conditions ranged by 2.5 orders of magnitude from 0.2 to 52 x 10-3m. Concurrently, a terrestrial laser scanner was used periodically to measure surface geometry and generate point clouds across the study site. Point clouds were processed and interpolated onto a regular grid for estimation of Z0 based on the geometry and distribution of surface roughness elements. Two different geometric evaluations, the Lettau and Counihan methods, were used for the estimation of Z0. The estimates based on surface geometry were evaluated and compared to anemometric Z0 values calculated from field observations of wind turbulence across the surface of the study site. The Lettau method Z0 values compared well to the measured anemometric results, with low but acceptable Nash-Sutcliffe Efficiency Coefficient (NSE) of 0.14 and a strong coefficient of determination (R2 = 0.90). While the NSE was small, the Lettau Z0¬ values could easily be scaled to the anemometric Z0. The Counihan method yielded less accurate results compared to the anemometric data, with a NSE of -1.1. The data also showed a strong correlation between Z0 and changing snow cover. The coefficient of determination between Z0 and snow-covered area for both the anemometric and Lettau methods was greater than 0.7, indicating that both methods responded well to changing surface conditions.
Open Access
Thresholds for runoff generation in ephemeral streams with varying morphology in the Sonoran Desert in Arizona, USA
(Colorado State University. Libraries, 2015) Faulconer, Joshua D., author; Kampf, Stephanie, advisor; MacDonald, Lee, committee member; Ronayne, Michael, committee member
In ephemeral streams, infrequent surface flow can be the main source of water that sustains plants throughout long dry periods. The objectives of this research are to: (1) explore seasonality of rainfall runoff in different channel types and (2) examine how runoff thresholds vary by channel type. The study area was two watersheds with areas of 188 km² and 323 km² on the Yuma Proving Grounds (YPG) in the Sonoran Desert near Yuma, Arizona. Eight tipping bucket rain gauges were installed to measure precipitation. Runoff was measured with 18 pressure transducers in five different channel types with different channel morphologies and contributing areas ranging from 0.002 km² to 225 km². Over approximately two years there were 11 to 48 rain events at the different rain gauges. Stream types with bedrock channels and small watershed areas between 0.005 km² and 0.015 km² produced runoff when the peak 60-minute precipitation intensity (I60) exceeded 4-6 mm hr⁻¹. At these sites, 17-25 percent of the rain storms generated runoff. I60 values of 5-9 mm hr⁻¹ produced runoff in streams with contributing areas of 0.021-0.061 km² on mid-Pleistocene piedmont surfaces covered by desert pavement. At these sites, 31-36 percent of rain events produced runoff. Streams incised into bedrock with some alluvium fill produced runoff at larger I60's of 13-18 mm hr⁻¹. Contributing areas for these sites were 0.8 km² to 2.2 km², and up to 10 percent of precipitation events at these sites produced flow. Precipitation thresholds for runoff generation in streams with contributing areas >3 km² were not clearly defined due to the influences of variable precipitation in upstream tributaries and transmission losses of streamflow through channel bed alluvium. For watersheds with <3km², rain intensity thresholds increased with the log of catchment area, and as a result flow frequency tended to decrease with increasing catchment area.
Open Access
Response of streamflow and stream chemistry to pine beetle induced tree mortality across northern Colorado
(Colorado State University. Libraries, 2015) Menger, Ashley Lynn, author; Stednick, John D., advisor; Fassnacht, Steven R., committee member; Ronayne, Michael C., committee member
The lodgepole pine (Pinus contorta) forests of western North America recently endured the most severe insect-induced mortality in recorded history. The hydrological and biogeochemical impacts of mountain pine beetle (Dendroctonous ponderosae) (MPB) induced die-off are uncertain even with recent conceptual and physical research. The purpose of this study is to provide insight into changes in annual water yield, streamflow generation mechanisms and stream water nutrient concentrations due to the recent MPB epidemic. To evaluate the possible impact, watersheds with varying amounts of MPB induced tree mortality in the north-central Colorado Rocky Mountains are examined. It was hypothesized that the canopy loss associated with the MPB epidemic has led to significant changes in annual water yield, streamflow generation mechanisms and stream water total nitrogen, nitrate, and total organic carbon (TOC) concentrations. Data stationarity analysis using the Mann-Kendall test showed no significant trend in annual water yield from 1991-2013 with increasing beetle-killed area. Annual mean isotopic signature (¹⁸O and ²H) analysis of rain, snow, soil water and stream water showed snow (44%) to be the largest contributor to annual streamflow followed by soil water (38%) and rain (14%). No correlation was found between any mean annual source water and percent beetle-killed area. Isotopic analysis of peak streamflow showed soil water (43%) and snow (42%) to be the largest contributors to peak flow. Snow's streamflow contribution was negatively correlated (p = 0.02) to percent beetle-killed indicating that snow as a source for streamflow decreased as a watershed had a higher proportion of MPB-killed trees. No correlation was found between rain or soil water as source waters to peak streamflow and percent beetle-killed. Stream water total nitrogen, nitrate and TOC concentrations and fluxes were not significantly changed by the MPB epidemic. There was no correlation between stream water total nitrogen, nitrate or TOC concentrations or flux and percentage of beetle-killed area. Even though Colorado's forests have been significantly impacted by MPB induced tree mortality, this study suggests that percentage of beetle-killed watershed area has had little impact on annual water yield and stream water nutrient levels. Source water contribution to streamflow is impacted as a result of MPB induced tree mortality as the fraction of peak streamflow from snow decreased with increasing percentage of beetle-killed area.
Open Access
Spatial precipitation trends and effects of climate change on the Hawai'ian Hualalai aquifer
(Colorado State University. Libraries, 2015) Hendricks, Alyssa Danielle, author; Fassnacht, Steven, advisor; Laituri, Melinda, committee member; Arabi, Mazdak, committee member
While trends in temperature are well studied and understood spatially and temporally at a multitude of scales, trends in precipitation are less understood. As the predominant source of groundwater recharge in Western Hawai'i, precipitation plays a vital role in maintaining tourism and industry throughout the Kona Region. Kaloko-Honokohau National Historical Park was established in 1978 to perpetuate and maintain traditional native Hawai'ian culture and the surrounding ecosystem, which is dependent on freshwater from the surrounding Hualalai Aquifer. Precipitation increases with elevation from the coast to approximately 1500 meters up the slope of Hualalai Volcano and then decreases to approximately 2000 meters. Western Hawai'i has a dense rain gauge network and changes in precipitation in the last several decades have been observed, though the rate sand significance of change is unclear. This study introduces a new method of integrated spatial analysis aimed at representing spatial trends in more detail. Using the Rainfall Atlas of Hawai'i, produced by the University of Hawai'i at Manoa, spatial trends from 1978-2007 were studied by annually adjusting the 30-year climate normal and calculating residuals between adjusted and observed precipitation. The Mann-Kendall and Sen's Slope statistical tests were used spatially to determine the rate and significance of change. This method was then compared with spatial interpolation by inverse distance weighting (IDW) and ordinary kriging to assess the differences in methods. Results from the integrated spatial analysis show an annual decrease of -8.42 x 10⁶ m³/year across the entire study area and a decrease of -4.62 x 10⁶ m³/year when only significant areas are considered. This can be compared with -10.8 x 10⁶ m³/year total and -0.64 x 10⁶ m³/year in significant areas from IDW and -8.41 x 10⁶ m³/year and -1.31 x 10⁶ m³/year respectively from ordinary kriging. On a monthly basis, both the integrated spatial analysis and IDW yield similar trends regarding an increase or decrease in the net volume entering the aquifer, however IDW underestimates the overall magnitude. The introduced integrated spatial analysis method provides an improved assessment of spatial trends that, while not limited to precipitation, can assist in broadening the limited knowledge of spatial precipitation trends across the globe.