Browsing by Author "Burgholzer, Robert William"

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    Advancing Water Security and Environmental Sustainability Through Evaluation of Water Use From the Field to State-Wide Scale
    Sangha, Laljeet Singh (Virginia Tech, 2023-01-17)
    The United States (US) has experienced a surge in water shortages and droughts in recent times. Water shortages can result from population growth, climate change, inadequate water management policies, and the improper use of available technologies. The existing data and research on water use associated with water management policy structures are limited. Many states in the US follow strict regulations on water discharge into streams to enforce water quality standards; however, water withdrawal restrictions from streams are limited and inadequate in terms of water management at times of low flow. In states such as Virginia (VA), the Virginia Department of Environmental Quality (VDEQ) requires a Virginia Water Protection (VWP) permit for all water withdrawals from VA's surface waters. However, under certain provisions of VWP regulations, users are exempted from having a permit. Such permit exemptions exist in many states and present a severe challenge to water supply management. Chapter 2 compares the impact of permit exemptions on surface water availability and drought flows and compares these impacts to the relatively well-studied risks presented by dry climate change and demand growth in Virginia (VA). It was observed that in some regions, the impacts under the exempt user scenario were higher than those under the dry climate change scenario. In addition, water supply managers and government agencies use user-reported water withdrawal data to develop water management programs. Irrigated agriculture is the largest source of water consumption in the US. However, water-reporting regulations exempt users from withdrawing water for irrigation under a certain threshold. Moreover, as water is not metered, users often do not report their irrigation water use, resulting in considerable uncertainty about the impacts of irrigation withdrawals, which could potentially impact other water users, lead to water shortages or conflicts, and negatively impact stream ecology. Chapter 3 focuses on developing a novel methodology for quantifying unreported irrigation water withdrawals using publicly available USDA-Census and USDA-IWMS datasets. This method was used to evaluate the unreported water withdrawals in the VA. Finally, water use practices at the field level intersect with other environmental issues at a larger scale. For example, irrigation practices can influence nutrient uptake and transport at the field level. Insufficient water for irrigation, especially during critical growth stages, results in yield and economic losses and reduces agricultural productivity. However, excessive irrigation can lead to wasted water and energy as well as runoff and leaching of nutrients and agricultural chemicals. Therefore, the adoption of technological advancements at the field scale can reduce the amount of water needed to fulfill the needs while mitigating any nutrient impacts on the soil due to the excessive use of water. This is highly important when fertilizer prices are always high. Chapter 4 focuses on quantifying the impact of the use of short-term weather forecast data in irrigation scheduling on nutrient and water use efficiency in humid climates: experimental results for corn and cotton. It was found that irrigation scheduling using short-term weather forecast data is helpful for improving the nutrient and water use efficiency of corn. For cotton, nutrient and water use efficiency are highly influenced by irrigation and precipitation with respect to the growth stage.
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    Consumptive Water Use: Refining State Water Supply Estimates with Discharge and Withdrawal Data
    McCarthy, Mary Morgan (Virginia Tech, 2019-06-11)
    Water scarcity has quickly become one of the most pressing issues in the 21st century. Knowledge of the stress consumption places on water supply is therefore necessary for improved resource management. This research leverages monthly facility level withdrawal and discharge data from two different sources to provide important observations of consumptive water use across several spatial scales and water use sectors in Virginia between 2010-2016. Consumptive water is defined as water which is withdrawn and not returned to a water resource system. Consumption was estimated on statewide, watershed, county, and facility levels. The agriculture/irrigation, aquaculture, commercial, industrial, energy, and municipal sectors were considered for analysis. Facilities were matched between the two data sources by narrowing potential matches by distance and then by facility name using an approximate string distance mechanism. This analysis revealed that inconsistent discharge reporting affects estimates of consumption through time and any errors at finer spatial scales are ultimately masked at coarser levels. Statewide energy consumption in Virginia was found to be between 4-20% considering all available data and 0.4-4% across matched facilities. Non-energy consumption was an estimated 37-51% considering all available data and only 28-33% across matched facilities. Inconsistent reporting of discharge made it difficult to determine if consumption trends truly exist in Virginia, but monthly consumption appears to be persistent through time and slightly increasing in non-energy sectors. Industrial consumption in Virginia was also found to be higher than literature values. Results from this study are beneficial for water supply modeling and planning by providing more refined estimates of the actual stress withdrawals place on water supply.
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    A Dam Conundrum: The Role of Impoundments in Stream Flow Alteration
    Brogan, Connor O'Beirne (Virginia Tech, 2018-09-12)
    Over the past century, the world's rivers have become increasingly impounded to combat water scarcity and fossil-fuel reliance. Large dams have faded from popularity due to their adverse environmental effects, but small ponds and reservoirs continue to be constructed at high rates. Due to limited data regarding their size and flow, it has been difficult to assess how these smaller impoundments impact rivers. This study combined rainfall runoff data from the Chesapeake Bay Model with the unique routing framework of VA Hydro to create a simplistic hydrologic model capable of analyzing impoundment-induced flow alteration. Using standard design techniques and satellite imagery, a methodology was developed to build realistic stage-storage-discharge relationships for small and large impoundments. Eleven impoundments of the Difficult Run watershed were modeled within VA Hydro to assess their cumulative impact on downstream flow. Multiple models were created with different active impoundments and run for the full model period, 1984 - 2005. Flow alteration increased significantly with additional impoundments. Peak flows were attenuated as water was stored behind outlets, but median flows were increased as this water was slowly released. Average storm duration increased due to extended rising and falling limbs caused by impoundment outlets. Headwater channels increasingly ran dry, decreasing extreme low flows due to impoundment evaporation. Large reservoirs had a greater impact on median flows, but smaller ponds dominated low flow alteration. These results suggest that traditional hydrologic assumptions and metrics may be incapable of analyzing a changing flow regime without explicitly considering small and large impoundments upstream.
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    Ecohydrologic Indicators of Low-flow Habitat Availability in Eleven Virginia Rivers
    Hoffman, Kinsey H. (Virginia Tech, 2015-10-26)
    Increasing demand and competition for freshwater is threatening instream uses including ecosystem services and aquatic habitat. A standard method of evaluating impacts of alternative water management scenarios on instream habitat is Instream Flow Incremental Methodology (IFIM). The primary outputs of IFIM studies are: 1) habitat rating curves that relate habitat availability to streamflow for every species, lifestage, or recreational use modelled; and 2) habitat time series under alternative water management scenarios. We compiled 428 habitat rating curves from previous IFIM studies across 11 rivers in Virginia and tested the ability to reduce this number based on similarities in flow preferences and responses to flow alteration. Individual site-species combinations were reduced from 428 objects to four groups with similar seasonal habitat availability patterns using a hierarchical, agglomerative cluster analysis. A seasonal habitat availability (SHA) ratio was proposed as a future indicator of seasonal flow preferences. Four parameters calculated from the magnitude and shape of habitat rating curves were proposed as response metrics that indicate how a lifestage responds to flow alteration. Univariate and multivariate analyses of variance and post-hoc tests identified significantly different means for the SHA ratio, QP (F=63.2, p<2e-16) and SK (F=65.6, p<2e-16). A reduced number of instream flow users can simplify the incorporation of aquatic habitat assessment in statewide water resources management.
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    Meteorological Impacts on Streamflow: Analyzing Anthropogenic Climate Change's Effect on Runoff and Streamflow Magnitudes in Virginia's Chesapeake Bay Watershed
    Hildebrand, Daniel Steven (Virginia Tech, 2020-08-05)
    Anthropogenic climate change will impact Virginia's hydrologic processes in unforeseen ways in the coming decades. This research describes variability in meteorology (temperature and precipitation) and associated hydrologic processes (evapotranspiration) throughout an ensemble of 31 general circulation models (GCMs) used by the Chesapeake Bay Program (CBP). Trends are compared with surface runoff generation patterns for a variety of land uses to investigate climate's effect on runoff generation. Scenarios representing pairings of the tenth, fiftieth, and ninetieth percentiles of precipitation and temperature in the CBP 31-model ensemble were run through VADEQ's VA Hydro hydrologic model to investigate streamflow's response to climate. Temperature changes across the study area were minimized in the tenth percentile scenario (+1.02 to +1.24◦C) and maximized in the ninetieth (+2.20 to +3.02◦C), with evapotranspiration change following this trend (tenth: +2.84 to +3.81%; ninetieth: +6.53 to +10.2%). Precipitation change ranged from -10.9 to -7.30% in the tenth to +22.1 to +28.0% in the ninetieth. Runoff per unit area was largely dependent on land use, with the most extreme changes in runoff often seen in forested and natural land uses (-24% in tenth; +53% in ninetieth) and the least extreme seen in impervious and feeding space land(tenth: -11%; ninetieth: +30%). Both overall runoff per unit area and streamflow changed drastically from the base in the tenth (-20.4% to -25.9% change in median runoff; -19.8% to -27.1% change in median streamflow) and ninetieth (+30.4% to +53.7% change in median runoff; +33.0% to +77.8% change in median streamflow) percentile scenarios.
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    Monitoring and Managing River Corridors in the Midst of Growing Water Demand
    Keys, Tyler Adam (Virginia Tech, 2018-04-26)
    Rivers and their surrounding riparian and subsurface ecosystems, known as river corridors, are important landscape features that provide a myriad of ecological and societal benefits. While the importance of riverine flooding has been widely acknowledged and extensively studied, very little research has been conducted on the interactions between river channels and their adjacent floodplains. The importance of this hydrologic connectivity between rivers and floodplains has been emphasized in recent decades and now ecological engineering techniques such as stream restoration are often utilized to restore connectivity between streams and their riparian ecosystems. Despite its ubiquity in practice, there are still many basic components of river-floodplain connectivity that are not well understood. Furthermore, a lack of cost-effective monitoring techniques makes sustainable management of river corridors quite challenging. Thus, the overall goals of my dissertation were: 1) develop user-friendly river corridor monitoring techniques utilizing cost-effective approaches such as time-lapse digital imagery and satellite remote sensing and 2) identify the effects of anthropogenic activities on river corridor hydrologic and biogeochemical processes that occur at varying spatial and temporal scales during flood events. These goals were addressed through five independent studies that span spatiotemporal scales. The five studies utilized a combination of novel remote sensing, hydrologic/hydraulic modeling, and high frequency spatial sampling techniques to analyze river corridor dynamics. Results highlight that digital imagery and satellite remote sensing can be effective tools for monitoring river corridors in data scare regions. Additionally, impounding streams and river corridors alters floodplain connectivity and biogeochemical processing of reactive solutes such as nitrogen and phosphorus. Findings from this work highlight the important role that spatial and temporal scale plays in river corridor dynamics. Overall, this research provides new analytical techniques and findings that can be used to effectively monitor and manage river corridors.
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    Understanding the role of scale in assessing sediment and nutrient loads from Coastal Plain watersheds delivered to the Chesapeake Bay
    Nayeb Yazdi, Mohammad (Virginia Tech, 2020-07-17)
    Urban and agricultural runoff is the principal contributor to non-point source (NPS) pollution and subsequent impairments of streams, rivers, lakes, and estuaries. Urban and agricultural runoff is a major source of sediment, nitrogen (N) and phosphorus (P) loading to receiving waters. Coastal waters in the southeastern U.S. are vulnerable to human impacts due to the proximity to urban an agricultural land uses, and hydrologic connection of the Coastal Plain to receiving waters. To mitigate the impacts of urban and agricultural runoff, a variety of stormwater control measures (SCMs) are implemented. Despite the importance of the Coastal Plain on water quality and quantity, few studies are available that focus on prediction of nutrient and sediment runoff loads from Coastal Plain watersheds. The overall goals of my dissertation are to assess the effect of urban and agricultural watershed on coastal waters through monitoring and modeling, and to characterize treatment performance of SCMs. These goals are addressed in four independent studies. First, we developed the Storm Water Management Model (SWMM) and the Hydrologic Simulation Program-Fortran (HSPF) models for an urbanized watershed to compared the ability of these two models at simulating streamflow, peak flow, and baseflow. Three separate monitoring and modeling programs were conducted on: 1) six urban land uses (i.e. commercial, industrial, low density residential, high density residential, transportation, and open space); 2) container nursey; and 3) a Coastal Plain retention pond. This study provides methods for estimating watershed pollutant loads. This is a key missing link in implementing watershed improvement strategies and selecting the most appropriate urban BMPs at the local scale. Results of these projects will help urban planners, urban decision makers and ecological experts for long-term sustainable management of urbanized and agricultural watersheds.
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    Using Accumulation Based Network Identification Methods to Identify Hill Slope Scale Drainage Networks in a Raster GIS
    Burgholzer, Robert William (Virginia Tech, 2005-02-10)
    The simple accumulation-based network identification method (ANIM) in a raster Geographic Information System (GIS) posed by O'Callaghan and Mark (1984) has been criticized for producing a spatially uniform drainage density (Tarboton 2002) at the watershed scale. This criticism casts doubt on the use of ANIMs for deriving properties such as overland flow length for nonpoint source pollution models, without calibrating the accumulation threshold value. However, the basic assumption that underlies ANIMs is that convergent topography will yield a more rapid accumulation of cells, and thus, more extensive flow networks, with divergent, or planar terrain yielding sparser networks. Previous studies have focused on networks that are coarser than the hill-slope scale, and have relied upon visual inspection of drainage networks to suggest that ANIMs lack the ability to produce diverse networks. In this study overland flow lengths were calculated on a sub-watershed basis, with standard deviation, and range calculated for sub-watershed populations as a means of quantifying the diversity of overland flow lengths produced by ANIM at the hill slope scale. Linear regression and Spearman ranking analyses were used to determine if the methods represented trends in overland flow length as suggested by manual delineation of contour lines. Three ANIMs were analyzed: the flow accumulation method (O'Callaghan and Mark, 1984), the terrain curvature method (Tarboton, 2000) and the ridge accumulation method (introduced in this study). All three methods were shown to produce non-zero standard deviations and ranges using a single support area threshold, with the terrain curvature method producing the most diverse networks, followed by the ridge accumulation method, and then the flow accumulation method. At an analysis unit size of 20 ha, the terrain curvature method produced a standard deviation that was most similar to those suggested by the contour crenulations, -13.5%, followed by the ridge accumulation method, -21.5%, and the flow accumulation method, -61.6%. The ridge accumulation produced the most similar range, -19.1%, followed by terrain curvature, -24.9%, and flow accumulation, -65.4%. While the flow accumulation networks had a much narrower range of predicted flow lengths, it had the highest Spearman ranking coefficient, Rs=0.722, and linear regression coefficient, R2=0.602. The terrain curvature method was second, Rs=0.641, R2=0.469, and then ridge accumulation, Rs=0.602, R2=0.490. For all methods, as threshold values were varied, areas of dissimilar morphology (as evidenced by the common stream metric stream frequency) experienced changes in overland flow lengths at different rates. This results in an inconsistency in ranking of sub-watersheds at different thresholds. When thresholds were varied to produce average overland flow lengths from 75 m to 150 m, the terrain curvature method showed the lowest incidence of rank change, 16.05%, followed by the ridge accumulation method, 16.73%, then flow accumulation, 25.18%. The results of this investigation suggest that for all three methods, a causal relationship exists between threshold area, underlying morphology, and predicted overland flow length. This causal relationship enables ANIMs to represent contour network trends in overland flow length with a single threshold value, but also results in the introduction of rank change error as threshold values are varied. Calibration of threshold value (varying threshold in order to better match observed overland flow lengths) is an effective means of increasing the accuracy of ANIM predictions, and may be necessary when comparing areas with different stream frequencies. It was shown that the flow accumulation method produces less diverse networks than the terrain curvature and ridge accumulation methods. However, the results of rank and regression analyses suggest that further investigation is required to determine if these more diverse ANIM are in fact more accurate than the flow accumulation method.