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Assessing Regional Gully Erosion Risk: A Remote Sensing and Geographic Information Systems Approach
Gully erosion has been established as a major source of sediment pollution in the upper Trinity River watershed in north-central Texas. This fact, along with a lack of models appropriate for a large-area gully erosion analysis established a need for a gully erosion study in the upper Trinity basin. This thesis project attempted to address this need by deriving an index indicative of gully erosion risk using remote sensing and geographic information systems (GIS) methodology. In context of previous field studies, the coarse spatial resolution of the input GIS data layers presented a challenge to prediction of gully prone areas. However, the remote sensing/GIS approach was found to provide useful reconnaissance information on gully risk over large areas.
Assessing the Spatial and Temporal Distribution of MTBE and BTEX Compounds in Lake Lewisville, Texas February 1999 - February 2000
The spatial and temporal distribution of Methyl Tertiary-Butyl Ether (MTBE) and BTEX (Benzene, Toluene, Ethylbenzene, Xylenes) compounds were assessed in a multipurpose reservoir, Lake Lewisville, Texas between February 1999 and February 2000. Concentrations of MTBE ranged from 0.0 - 16.7 mg/L. Levels of MTBE in the lake were related to watercraft. BTEX concentrations were never detected above 2.0 mg/L during the sampling period. Finished drinking water from Denton and the Upper Trinity Regional Water District (UTRWD) Treatment Plants were also tested for MTBE and BTEX. MTBE and BTEX were not detected in UTRWD water samples. Denton's finished water samples never exceeded 2.2 mg/L for MTBE and BTEX was not detected except for one replicate of 1.1 mg/L toluene.
Assessment of Radio-Tagged Grass Carp (Ctenopharnygodon idella) Dispersion, Vegetation, and Temperature Preferences in North Lake Reservoir
Twenty-nine (Group One, June 8,1995) grass carp (Ctenopharyngodon idella) and five (Group Two, April 18, 1996) grass carp were radio-tagged to monitor movement patterns and habitat preferences on North Lake, a 335 hectare multi-use reservoir located in Irving, Texas. Overall fish mean Average Daily Movement (ADM) rates were 49.2 meters/day (during Half One, 6/8/95-11/30/95) and 5.3 meters/day (during Half Two, 12/14/95-6/6/96). Aquatic macrophtye distribution data were obtained. Radio-tagged grass carp were located in Hydrilla verticillata infested areas increasingly throughout the study, however, percent frequency of Hydrilla along 15 transects did not decrease. Radio-transmitters were equipped with temperature-sensors (10-35 Celsius range). Results indicated that radio-tagged grass carp showed no avoidance of areas of North Lake with elevated water temperatures. Radio-tagged grass carp dispersed quickly from stocking point, then moved into littoral areas infested with Hydrilla. After an initial movement period, most fish remained in a localized area.
An Assessment of Storm Water Toxicity from the Dallas/Fort Worth Metroplex and Denton, Texas
With the advent of national storm water regulations, municipalities with populations greater than 100,000 are required to obtain National Pollutant Discharge Elimination System Permits (NPDES) for storm water discharges. In addition to the sampling required for the permit process, the City of Fort Worth contracted with the University of North Texas' Institute of Applied Sciences to conduct acute toxicity testing using Pimephales prcmelas and Ceriodaphnia dubia on storm water samples received from the Dallas/Fort Worth Metroplex. A Toxicity Identification Evaluation (TIE) was performed on four samples that exhibited acute toxicity to C. dubia. High levels of metals as well as diazinon were some of the probable toxicants found.
An Assessment of the Use of Seeding, Mowing, and Burning in the Restoration of an Oldfield to Tallgrass Prairie in Lewisville, Texas
An examination of the effectiveness of seeding, burning, and mowing in the reestablishment of tallgrass prairie species on overgrazed and abandoned pastureland. The study site is a 20 acre tract on U.S. Corps of Engineers land below Lake Lewisville in Denton County, Texas. The site was partitioned into thirty-nine 40 by 40 meter plots with seeding (carried out in 1996) and management treatment (burning, mowing, and no maintenance carried out in 1998) randomly applied following a two level design. For each plot, nine stratified-random 0.1 m2 subplots were examined and shoot counts for each species recorded. The effects of the treatments on individual species and species richness were analyzed with a two-way ANOVA followed by a SNK multiple range test, both on ranked data. Community level analysis was conducted with both a MANOVA on ranked data and a Canonical Correspondence Analysis on raw data. Results indicate that seeding positively affected species richness, particularly when combined with either burning or mowing in the early spring. Mowing also significantly increased species richness in areas that were not seeded, while burning negatively affected species richness on unseeded plots. Treatments significantly affected community composition with treatments having the most clear effect on spring and summer forbs.
Biomonitoring at Dallas-Fort Worth International Airport: Relating Watershed Land Use with Aquatic Life Use
The Dallas-Fort Worth International (DFW) Airport is located in a densely urbanized area with one of the fastest-growing populations in the U.S.A. The airport property includes a large tract of "protected" riparian forest that is unique to the urban surroundings. This dissertation explores variables that influence the benthic macroinvertebrate community structure found in urbanized prairie streams that were initially assessed by the University of North Texas (UNT) Benthic Ecology Lab during four, non-consecutive biomonitoring studies (2004, 2005, 2008, and 2014) funded by the DFW Airport. Additionally, land use analysis was performed using 5-meter resolution satellite imagery and eCognition to characterize the imperviousness of the study area watersheds at multiple scales. Overall, flow conditions and imperviousness at the watershed scale explained the most variability in the benthic stream community. Chironomidae taxa made up 20-50% of stream communities and outperformed all other taxa groups in discriminating between sites of similar flows and urban impairments. This finding highlights the need for genus level identifications of the chironomid family, especially as the dominant taxa in urban prairie streams. Over the course of these biomonitoring survey events, normal flow conditions and flows associated with supra-seasonal drought were experienced. Prevailing drought conditions of 2014 did not negatively influence stream communities, allowing this study to capture the long-term natural (temporal) variability of urban prairie stream communities. Such long-term studies are imperative for discerning between stream impairment versus natural variation, especially as droughts become more frequent and severe.
Comparison of Risk Assessment-Predicted Ecologically Safe Concentrations of Azinphos-Methyl and Fenvalerate to Observed Effects on Estuarine Organisms in a South Carolina Tidal Stream Receiving Agricultural Runoff
A prospective ecological risk assessment method was developed evaluating the cumulative probabilistic impact of chemical stressors to aquatic organisms. This method was developed in response to the need to evaluate the magnitude, duration and episodic nature of chemical stressors on aquatic communities under environmental exposure scenarios. The method generates a probabilistic expression of the percent of an ecosystem's species at risk from a designated chemical exposure scenario.
Developing a Forest Gap Model to Be Applied to a Watershed-scaled Landscape in the Cross Timbers Ecoregion Using a Topographic Wetness Index
A method was developed for extending a fine-scaled forest gap model to a watershed-scaled landscape, using the Eastern Cross Timbers ecoregion as a case study for the method. A topographic wetness index calculated from digital elevation data was used as a measure of hydrologic across the modeled landscape, and the gap model modified to have with a topographically-based hydrologic input parameter. The model was parameterized by terrain type units that were defined using combinations of USDA soil series and classes of the topographic wetness index. A number of issues regarding the sources, grid resolutions, and processing methods of the digital elevation data are addressed in this application of the topographic wetness index. Three different grid sizes, 5, 10, and 29 meter, from both LiDAR-derived and contour-derived elevation grids were used, and the grids were processed using both single-directional flow algorithm and bi-directional flow algorithm. The result of these different grids were compared and analyzed in context of their application in defining terrain types for the forest gap model. Refinements were made in the timescale of gap model’s weather model, converting it into a daily weather generator, in order to incorporate the effects of the new topographic/hydrologic input parameter. The precipitation model was converted to use a Markov model to initiate a sequence of wet and dry days for each month, and then daily precipitation amounts were determined using a gamma distribution. The output of the new precipitation model was analyzed and compared with a 100-year history of daily weather records at daily, monthly, and annual timescales. Model assumptions and requirements for biological parameters were thoroughly investigated and questioned. Often these biological parameters are based on little more than assumptions and intuition. An effort to base as many of the model’s biological parameters on measured data was made, including a new …
Environmental Factors Influencing Chlorophyll-a Concentrations in Lake Texoma
An analysis of algal biomass measured by chlorophyll-a concentration in Lake Texoma was performed as a part of a monitoring program to develop baseline environmental data in order to detect the potential effects of engineered changes in chloride concentrations in the reservoir. This portion of the research project focused on two main research objectives. The first objective was evaluating the effect of sampling strategy on the ability to adequately reflect standing crop estimates and trends in algal biomass. Two sampling regimes utilizing replication of three versus ten samples were applied and then analyzed using a minimum detectable difference algorithm to determine the necessary magnitude of replication to represent the variation in the metric. Chlorophyll-a distribution was analyzed for zonation patterns expected in a river-run reservoir to establish the importance of representative sampling of river, transition and main lake zones of the reservoir for management decisions and trophic characterization.
Estimated Extent and Fate of Chlorinated Solvent Contamination in the Soil of the Naval Air Station, Dallas, Texas
This thesis estimates the spatial extent of chlorinated solvent contamination of the soil at the Naval Air Station, Dallas, then estimates the fate and transport of these contaminants, over time, using the Soil Transport and Fate database and the Vadose-Zone Interactive Processes (VIP) modeling software. Geostatistical analysis identifies two areas with serious chlorinated solvent contamination. Fate and transport modeling estimates that this contamination will degrade and disperse from the soil phase to below regulatory limits within one year, although there is a risk of groundwater contamination. Contaminants are estimated to persist in the water and air phases of the soil. Further sampling is recommended to confirm the results of this study.
An Evaluation of Fish and Macroinvertebrate Response to Effluent Dechlorination in Pecan Creek
This study evaluated the effects of chlorinated effluent discharged from the City of Denton, Texas' wastewater treatment plant on Pecan Creek's fish and macroinvertebrate assemblages, and their recovery upon dechlorination. A baseline of ecological conditions was established while chlorine was present in the effluent (June 1993- October 1993), and was evaluated again after dechlorination with sulfur dioxide (October 1993-August 1994). In situ Asiatic clam and fathead minnow ambient toxicity tests, and fish and macroinvertebrate collections were used to establish this baseline for comparison to post-dechlorination results.
The Influence of Urban Green Spaces on Declining Bumble Bees (Hymenoptera: Apidae)
Bumble bees (Bombus spp.) are adept pollinators of countless cultivated and wild flowering plants, but many species have experienced declines in recent decades. Though urban sprawl has been implicated as a driving force of such losses, urban green spaces hold the potential to serve as habitat islands for bumble bees. As human populations continue to grow and metropolitan areas become larger, the survival of many bumble bee species will hinge on the identification and implementation of appropriate conservation measures at regional and finer scales. North Texas is home to some the fastest-growing urban areas in the country, including Denton County, as well as at least two declining bumble bee species (B. pensylvanicus and B. fraternus). Using a combination of field , molevular DNA and GIS methods I evaluated the persistence of historic bumble bee species in Denton County, and investigated the genetic structure and connectivity of the populations in these spaces. Field sampling resulted in the discovery of both B. pensylvanicus and B. fraternus in Denton County's urban green spaces. While the relative abundance of B. fraternus in these spaces was significantly lower than historic levels gleaned from museum recors, that of B. pensylvanicus was significantly higher. Statistical analyses found that both bare ground and tree cover surrounding sample sites were negatively associated with numbers of bumble bee individuals and hives detected in these green spaces. Additionally, limited genetic structuring of bumble bee populations was detected, leading to the conclusion that extensive gene flow is occurring across populations in Denton County.
Informing Conservation Management Using Genetic Approaches: Greater Sage-Grouse and Galápagos Short-Eared Owls as Case Studies
Small isolated populations are of particular conservation interest due to their increased extinction risk. This dissertation investigates two small wild bird populations using genetic approaches to inform their conservation. Specifically, one case study investigated a Greater Sage-grouse (Centrocercus urophasianus) population located in northwest Wyoming near Jackson Hole and Grand Teton National Park. Microsatellite data showed that the Jackson sage-grouse population possessed significantly reduced levels of neutral genetic diversity and was isolated from other Wyoming populations. Analysis with single nucleotide polymorphisms (SNPs) and microsatellite data provided further evidence that the population's timing of isolation was relatively recent and most likely due to recent anthropogenic habitat changes. Conservation recommendations include maintaining or increasing the population's current size and reestablishing gene flow with the nearest large population. The second case study investigated the genetic distinctiveness of the Floreana island population of the Galápagos Short-eared Owl (Asio flammeus galapagoensis). Mitochondrial DNA sequence data did not detect differences across nine island populations, yet microsatellite and morphometric data indicated that limited gene flow existed with the population and surrounding island populations, which appeared asymmetric in direction from Floreana to Santa Cruz with no indication of gene flow into Floreana. These results have important conservation implications and recommend that the Floreana Short-eared Owl population be held in captivity during the rodenticide application planned for an ecosystem restoration project in 2018. The population is less likely to receive immigrants from surrounding island populations if negatively effected by feeding on poisoned rodents.
Interspecific Competition Between Hygrophila polysperma and Ludwigia repens, Two Species of Importance in the Comal River, Texas
Hygrophila polysperma is a plant native to Asia that has been introduced into the Comal River, TX and is thriving while Ludwigia repens, a species native to the river appears to be declining. Both plants have similar morphologies and occupy similar habitats in the river. Two plant competition experiments were conducted to examine the competitive interactions between the two species. First, an experimental design was developed in which established Ludwigia plants were 'invaded' by sprigs of Hygrophila to determine if established Ludwigia populations would be negatively impacted by invasion. The second experiment focused on establishment and growth of sprigs of each species under three competition scenarios. Results show that the continued growth of well-established Ludwigia plants was significantly depressed by the invasion of Hygrophila in comparison with those that had not been invaded. Furthermore, the growth of Hygrophila sprigs was uninhibited by the presence of Ludwigia, but the presence of Hygrophila negatively impacted the growth of Ludwigia sprigs. There was no difference in the growth of Hygrophila sprigs whether planted alone, with Ludwigia sprigs or even if planted into stands of established Ludwigia.
Long-Term Citizen Science Water Monitoring Data: An Exploration of Accuracy over Space and Time
The Texas Stream Team (TST) is one of an increasing number of citizen science water monitoring programs throughout the US which have been continuously collecting surface water quality data under quality assurance protocols for decades. Volunteer monitoring efforts have generated monitoring datasets that are long-term, continuous, and cover a large geographic area - characteristics shown to be valuable for scientists and professional agencies. However, citizen science data has been of limited use to researchers due to concerns about the accuracy of data collected by volunteers, and the decades of water quality monitoring data collected by TST volunteers is not widely used, if at all. A growing body of studies have attempted to address accuracy concerns by comparing volunteer data to professional data, but this has rarely been done with large-scale, existing datasets like those collected by TST. This study assesses the accuracy of the volunteer water quality data collected across the state of Texas by the TST citizen science program between 1992-2017 by comparing it to professional data from corresponding stations during the same time period, as well as comparing existing and experimental data from a local TST partner agency. The results indicate that even large-scale, existing volunteer and professional data with unpaired samples that may have been taken months apart can show statewide agreement of 80% for all parameters (DO = 77%, pH = 79%, conductivity = 85%) over the 38 years of sampling included in the analyses, across all locations. The local case study using paired datasets for which a greater number of factors were controlled for show an even higher agreement between volunteers and professionals (DO = 91%, pH = 87%, conductivity = 100%) and show no significant difference between experimental and existing sampling data. The results from this study indicate that TST has been collecting water …
Monitoring Watershed Health in the Upper Trinity River Basin, North Central Texas
This study conducts watershed analysis using biological and geo-spatial techniques. Incorporating landscape features with biological attributes has been shown to be an effective method of monitoring environmental quality within watersheds. In situ biomonitoring using the Asiatic Clam, Corbicula fluminea, habitat suitability, and water quality data were evaluated for their potential to describe ecological conditions in agricultural and urban areas within the Upper Trinity River watershed. These data were analyzed with GIS to identify effects of land use on ecological conditions. C. fluminea downstream of point source effluents was effective detecting in-stream toxicity. Ambient toxicity appears to have improved in the Trinity, although urban influences limit aspects of aquatic life. No association between habitat quality and land use was identified.
Ozone Pollution Monitoring and Population Vulnerability in Dallas-Ft. Worth: A Decision Support Approach
In urban environments, ozone air pollution, poses significant risks to respiratory health. Fixed site monitoring is the primary method of measuring ozone concentrations for health advisories and pollutant reduction, but the spatial scale may not reflect the current population distribution or its future growth. Moreover, formal methods for the placement of ozone monitoring sites within populations potentially omit important spatial criteria, producing monitoring locations that could unintentionally underestimate the exposure burden. Although air pollution affects all people, the combination of underlying health, socioeconomic and demographic factors exacerbate the impact for socially vulnerable population groups. A need exists for assessing the spatial representativeness and data gaps of existing pollution sensor networks and to evaluate future placement strategies of additional sensors. This research also seeks to understand how air pollution monitor placement strategies may neglect social vulnerabilities and therefore, potentially underestimate exposure burdens in vulnerable populations.
Photo-induced Toxicity of Deepwater Horizon Spill Oil to Four Native Gulf of Mexico Species
The 2010 Deepwater Horizon oil spill resulted in the accidental release of millions of barrels of crude oil into the Gulf of Mexico (GoM). Photo-induced toxicity following co-exposure to ultraviolet (UV) radiation is one mechanism by which polycyclic aromatic hydrocarbons (PAHs) from oil spills may exert toxicity. Blue crab (Callinectes sapidus) are an important commercial and ecological resource in the Gulf of Mexico and their largely transparent larvae may make them sensitive to PAH photo-induced toxicity. Mahi-mahi (Coryphaena hippurus), an important fishery resource, have positively buoyant, transparent eggs. These characteristics may result in mahi-mahi embryos being at particular risk from photo-induced toxicity. Red drum (Sciaenops ocellatus) and speckled seatrout (Cynoscion nebulosus) are both important fishery resources in the GoM. They spawn near-shore and produce positively buoyant embryos that hatch into larvae in about 24 h. The goal of this body of work was to determine whether exposure to UV as natural sunlight enhances the toxicity of crude oil to early lifestage GoM species. Larval and embryonic organisms were exposed to several dilutions of water accommodated fractions (WAF) from several different oils collected in the field under chain of custody during the 2010 spill and two to three gradations of natural sunlight in a factorial design. Here, we report that co-exposure to natural sunlight and oil significantly reduced larval survival and embryo hatch compared to exposure to oil alone.
Plankton Community Response to Dechorination of a Municipal Effluent Discharged into the Trinity River
Chorine is used by the Village Creek Waste Water Treatment Plant to kill pathogenic microorganisms prior to discharge of the effluent into the Trinity River. The residual chlorine in the river impacted aquatic life prompting the U.S. Environmental Protection Agency in December 1990 to require dechlorination using sulfur dioxide. One pre-dechlorination and four post-dechlorination assessments of phytoplankton, periphyton, and zooplankton communities were conducted by the Institute of Applied Sciences at the University of North Texas. Dechlorination had no effect on the phytoplankton community. The periphyton community exhibited a shift in species abundance with a more even distribution of organisms among taxa. No change occurred in zooplankton species abundance, however, there was a decrease in zooplankton density following dechlorination.
Pretreatment Optimization of Fiberglass Manufacturing Industrial Wastewater
Wastewater effluent produced in the fiberglass manufacturing industry contains a significant amount of total suspended solids. Environmental regulations require pretreatment of effluent before it is discharged to the municipal wastewater treatment plant. Chemical precipitation by coagulation and flocculation is the method of pretreatment used at the Vetrotex CertainTeed Corporation (VCT). A treatability study was conducted to determine conditions at which the VCT Wastewater Pretreatment Plant could operate to consistently achieve a total suspended solids concentration ≤ 200-mg/L. Jar tests varied pH, polymer dosage, and ferric sulfate dosage. Total suspended solids and turbidity were measured to evaluate treatment performance. The data were used to determine an optimum set of conditions under project guidelines. Of twelve polymers screened, BPL 594 was selected as the most effective polymer. For cost efficiency in the wastewater pretreatment operation, recommendations suggested that treatment chemical injection be electronically controlled according to turbidity of the treated effluent.
Recovery of the Fish Population of a Municipal Wastewater Dominated, North Texas Creek After a Major Chlorine Disturbance
This study evaluated the effects of a major chlorine disturbance on fish communities in Pecan creek by the City of Denton's Pecan Creek Water Reclamation Plant. Fish communities in Pecan Creek were sampled using a depletion methodology during February, April, July, and November, 1999. February and April sampling events showed that the fish communities were severely impacted by the chlorine. Sampling during July and November showed fish communities recovered in Pecan Creek. The first-twenty minutes of shocking and seining data were analyzed to mirror an equal effort methodology. This methodology was compared to the depletion methodology to see if the equal effort methodology could adequately monitor the recovery of Pecan Creek after the chlorine disturbance. It was determined that the equal effort methodology was capable of monitoring the recovery of Pecan Creek, but could not accurately represent the fisheries community as well as the depletion method. These data using the twenty-minute study were compared to a previous study. Results of this study were similar to those found in a previous study, although fish communities were more severely impacted and took longer to recover.
Simulating Thermal and Chemical Spills in Coupled Cooling Reservoirs
Hot water discharges and potential chemical spills are factors that threaten water quality in cooling reservoirs of chemical and power plants. In this thesis, three models are used to analyze the impact of these factors in a particular case study.
Spatial and Temporal Patterns of Areal and Volumetric Phytoplankton Productivity of Lake Texoma
Phytoplankton productivity of Lake Texoma was measured for one year from August 1999 to August 2000 for four stations, using the oxygen change method and laboratory incubation. Mean values of the photosynthetic parameters, PBmax and alphaB ranged from 4.86 to 46.39 mg O2.mg Chl-1.hr-1 for PBmax and 20.06 to 98.96 mg O2.mg Chl-1.E-1.m2 for alphaB. These values were in the range to be expected for a highly turbid, temperate reservoir. Estimated gross annual areal productivity ranged from 594 g C.m2.yr-1 (P.Q. = 1.2), at a station in the Washita River Zone to 753 g C.m2.yr-1 at a station in the Red River Zone, of the reservoir. Gross annual areal productivity at Station 17, in the Main Lake Zone, was 708 g C.m2.yr-1. Gross areal and volumetric productivity showed distinct seasonal variation with Photosynthetically Available Radiation (PAR) and temperature. Trophic status estimated on a station-by-station basis, using net productivity values derived from gross productivity and respiration estimates, was mesotrophic for all the stations, though one station approached eutrophy. Net productivity values ranged from 0.74 to 0.91 g C. m-2.d-1. An algal bioassay conducted at two stations in August 2000, revealed that phosphorus was most likely the nutrient limiting photosynthesis at both these stations, although the more turbid riverine station was primarily light-limited.
The Tarrant County Atlas for Planning: A Geographic Information System for Open Space Design
This project demonstrates the construction of a land planning geographic information system (GIS) for Tarrant County, and explores how the technology could be used to select sites for a county wide open space preservation plan. As Texas' Tarrant County continues to undergo rapid change due to growth and expansion, the need for proactive, resourceful community planning is greater than ever. One crucial issue facing the region is how to preserve open areas that serve the county's citizens' ecological, recreational, cultural and economic needs. In order to assess how much open space is needed and which sites should be considered for special attention, large amounts of varied spatial information must be analyzed. The answer to effectively dealing with such data sets is a geographic information system (GIS) that stores all pertinent data digitally and allows for its manipulation through use of a computer software package. This project demonstrates the construction of a land planning GIS for Tarrant County, and explores how the technology could be used to select sites for a county wide open space preservation plan.
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