Teresa B Culver

University of Virginia | UVa · Department of Civil and Environmental Engineering (CEE)

Nonpoint source (NPS) water quality trading (WQT) is a market-based approach to improving water quality. Past work has shown that these programs could increase localized pollutant loadings, in part by exporting water quality controls from urban to rural areas. Virginia's NPS WQT program has enabled thousands of transactions and may provide a model...

Bioretention systems have the potential of simultaneous runoff volume reduction and nitrogen removal. Internal water storage (IWS) layers and real-time control (RTC) strategies may further improve performance of bioretention systems. However, optimizing the design of these systems is limited by the lack of effective models to simulate nitrogen tran...

A process-based nitrogen model suitable for urban stormwater Best Management Practices (BMPs), when used as an extension to current stormwater models, can assist decision-making by predicting nitrogen removal performances. While such a model has not been created, process-based nitrogen modules for agricultural fields have been developed and applied...

Reinforcement learning agents can learn real-time stormwater system control strategies that balance the competing goals of flood mitigation and sediment capture in urban watersheds.

Numerous studies have documented the linkages between agricultural nitrogen loads and surface water degradation. In contrast, potential water quality improvements due to agricultural best management practices are difficult to detect because of the confounding effect of background nitrate removal rates, as well as the groundwater‐driven delay betwee...

Active stormwater control may play an important role in mitigating urban flooding which is becoming more common with climate change and sea level rise. In this paper we describe and demonstrate swmm_mpc, software we developed for simulating model predictive control (MPC) for urban drainage systems using open source software (Python and the EPA Stor...

Uncertainties about the age of base-flow discharge can have serious implications for the management of degraded environmental systems where subsurface pathways, and the ongoing release of pollutants that accumulated in the subsurface during past decades, dominates the water quality signal. Numerical groundwater models may be used to estimate ground...

Promising environmental mechanisms to control malaria are presently underutilized. Water level fluctuations to interrupt larval development have recently been studied and proposed as a low-impact malaria intervention in Ethiopia. One impediment to implementing such new environmental policies is the uncertain impact of climate change on water resour...

As hydropower dam construction in rapidly growing economies dislodges communities, rural development experts must help the displaced make their livelihoods in new lacustrine environments. One question is whether the dam infrastructure can directly benefit those who remain within the vicinity of the reservoir. Integrated water resource management se...

This work presents a new paradigm for the design of stormwater detention basins. Through simulation and optimization, this work seeks to find the design of a detention basin outlet control structure that reduces the ecological impairment to downstream water bodies. Ecological impairment is measured using the ecodifference, a metric that represents...

As hydropower dam construction in rapidly growing economies dislodges communities, rural development experts must help the displaced make their livelihoods in new lacustrine environments. One question is whether the dam infrastructure can directly benefit those who remain within the vicinity of the reservoir. Integrated water resource management se...

Through a simulation modeling approach, this paper seeks to modify the design of detention ponds to preserve the natural ecological flows while satisfying the requisite regulatory flow requirements. This paper will utilize an innovative ecological flow paradigm: the ecoflow statistics. The ecoflow statistics consist of nine hydrological flow statis...

Across the U.S., combined sewer overflows (CSOs) pose a serious threat to water quality in thousands of lake, river, and coastal ecosystems. The Milwaukee Metropolitan Sewerage District (MMSD) operates an extensive system of sanitary sewers to collect and convey wastewater originated by local sewer systems in a 420 sq. mile service area. The main c...

The objective of this research is to develop and demonstrate a methodology to specifically assess the interrelationships among estimated precipitation, observed streamflow, and hydrologic model performance. To satisfy this objective, this work introduces a new concept called "precipitation fidelity," which is the correspondence of stream outflow to...

The indicators of hydrologic alteration (IHA) is a statistical flow methodology for characterizing ecologically important stream-flows. Typically, IHA has been used to identify the extent of human effects on a stream's hydrology and to set management goals to restore the stream ecology. In this work, the use of the seven "extreme low flow" statisti...

This paper investigates the water resources implications of using a method of hydrological control to reduce malaria around the Koka reservoir in central Ethiopia. This method is based on recent findings that malaria is transmitted from the shoreline of the Koka reservoir, and on a similar method that was used to control malaria some 80 yr ago in t...

Predictions from complex watershed models are relied on by policy-makers for resource allocations and development decisions. However, most managers do not have access to effective and practical approaches to represent the uncertainty within these systems and within the complex models; nor can they readily incorporate uncertainty into the decision p...

Although the aquifers below the Eastern Shore of Virginia serve as the region's only sources of fresh water, increased development and intensifying groundwater demands have put this resource at risk. Simulation modeling is used as a tool to evaluate impacts of groundwater withdrawals on the aquifers. Using available monitoring data, a regional thre...

During development of a Total Maximum Daily Load (TMDL) allocation, the costs associated with the requisite control measures, typically Best Management Practices (BMPs), should be considered. The simple premise that minimizing load reductions will also minimize cost cannot be substantiated, since the costs are governed by factors beyond performance...

Identifying and quantifying the critical elements in a water distribution system has traditionally involved a great deal of judgment. With the coming of computerized hydraulic analysis, it became easier to "fail" a pipe in a distribution system to assess its impact on service. However, when a failure occurs in a real system, it does not remove a si...

This study applied a generalized likelihood uncertainty estimation (GLUE) approach to a Hydrological Simulation Program-Fortran (HSPF) model used for the simulation of hydrology and transport of fecal coliform bacteria at Moore's Creek, Va. The procedures of the GLUE application to Moore's Creek HSPF model include: (1) a Latin hypercube sampling ap...

The use of genetic algorithms for the dynamic optimal design of pump-and-treat groundwater remediation systems is demonstrated through two new dynamic formulations. In the first formulation in which the contaminant sorption was assumed to be in equilibrium, the lengths of management periods were decision variables. The second formulation assumed a...

Uncertainty originates from the variability in efficacy of the control measures, or Best Management Practices (BMP), used to implement a Total Maximum Daily Load (TMDL) allocation. A sustainable TMDL allocation should take into account this source of uncertainty at the implementation phase. This study characterizes the uncertainties in the pollutan...

Uncertainties in input parameters, such as hydraulic conductivities, may result in inconsistencies between simulated and observed groundwater flows and contaminant plumes. If a groundwater management model for aquifer remediation design is based upon incorrect input, non-optimal remediation policies may result. Typically, aquifer uncertainties have...

Optimization modeling has been shown to be an important tool for cost-effective groundwater remediation. Currently most optimal remediation design tools are deterministic, assuming full knowledge of all inputs. Those that include uncertainty, typically utilize a random sampling of possible conductivity fields as input, with each realization presume...

Hydrological calibration of mechanistic watershed simulation models often requires several years of continuous flow data. Unfortunately, historical flow information is highly limited for many ungauged or recently gauged watersheds. Synthetic flow generation methods could be used to extend the available flow records at data-limited watersheds and to...

The design of a compacted soil liner that includes sorptive amendments is presented and evaluated as a combinatorial optimization problem. An objective function based oil the materials costs. Opportunity costs. and construction costs of the liner was used to evaluate the effect of incorporating four sorptive materials: benzyltriethylammnonium-bento...

To account for uncertainty in the form of variability and incomplete knowledge in Total Maximum Daily Load (TMDL) studies, a Margin of Safety (MOS) is introduced, typically chosen arbitrarily to be 5%. This study characterizes significant uncertainties present in loading rates by using multiple scenarios that each act as real potential loads to the...

Uncertainties in input parameters, such as hydraulic conductivities may result in inconsistencies between simulated and observed groundwater flow and transport data. If a groundwater management model for aquifer remediation design is based upon incorrectly estimated flow and transport parameter data, non-optimal remediation policies may result. To...

The determination of the pollutant load distribution among different pollutant sources in a watershed is a critical step in total maximum daily load (TMDL) development. Under current TMDL practices, TMDL allocations are typically determined through a trial-and-error approach of reducing pollutant loadings until a watershed simulation model predicts...

Given the inherent uncertainty in groundwater management problems uncertainty in determining aquifer parameter values, identifying an optimal remediation strategy based on a deterministic description of the system may not yield an optimal and feasible design. This work builds on the robust genetic algorithm (GA) developed by Chan Hilton and Culver....

The impacts of physical and chemical aquifer heterogeneities on optimal remediation design, costs, and time to compliance are investigated by linking a genetic algorithm with a contaminant transport simulation model. Physical and chemical aquifer heterogeneities were grouped into three levels as follows: (1) hydraulic conductivity (K) heterogeneity...

To cost-effectively restore contaminated sites to productive use requires integrated planning of cleanup and reuse. Ultimate reuse objectives should guide remediation decisions, instead of being dictated by pre-described remediation plans. This study links a robust groundwater remediation approach with reuse planning. A genetic algorithm optimizer...

The determination of how pollutant loads should be distributed among different pollutant sources in the watershed, which is known as pollutant load allocation, is a critical step in Total Maximum Daily Load (TMDL) development. Under current TMDL practices, TMDL allocations are typically determined through a trial-and-error approach of reducing poll...

Two different optimal design models are used to compare pulsed and continuous pumping remediation schemes for mass transfer-limited aquifers. All optimal design models couple a genetic algorithm with a flow and transport simulation model. The static pulsed pumping design model compares pulsed pumping with multiple management periods to continuous p...

An analysis of the impact of total maximum daily load (TMDL) allocations on the potential leaching of nitrates to groundwater in the Muddy Creek/Dry River watershed of Virginia is presented. The Muddy Creek/Dry River watershed has experienced nitrate impairments to both surface water and groundwater. Using the Nitrate Leaching and Economic Analysis...

This work explores the sensitivity of optimal remedial design policies and their associated costs to the residual constraint violation, which is the sum of any small violations in constraints that may occur over all points of interest. To evaluate the sensitivity, a genetic algorithm is used to solve two different groundwater remediation design pro...

The impact of physical and chemical aquifer heterogeneities on optimal remediation design and costs is investigated by linking a genetic algorithm optimization library with a contaminant transport simulation model. Various levels of physical and chemical (sorption) aquifer heterogeneities are examined. In the first level, heterogeneity is limited t...

The development of the Nitrate Total Maximum Daily Load (TMDL) for the Muddy Creek/Dry River watershed in Virginia illustrates important factors leading to successful completion and approval of a TMDL, while also revealing limitations to effective, accurate water quality management within the TMDL program. The Muddy Creek/Dry River watershed, which...

One of the key challenges in the TMDL development is how to define the critical condition for a receiving water body. When point sources and nonpoint sources are considered in an “integrated” manner, the worst-case scenario is not obviously known because of the fact that pollutant loads come from both constant flow point sources and storm-driven, t...

There always exists some degree of uncertainty associated with groundwater problems, often in determining the aquifer parameter values. Therefore finding an optimal remediation strategy based on a deterministic description of the system may not yield an optimal and feasible design. This work develops a genetic algorithm (GA) approach that takes int...

There often is difficulty enforcing the given constraints when applying a genetic algorithm (a flexible stochastic search method) to optimal ground-water remediation design problems. This paper compares two methods for constraint handling within the genetic algorithm framework. The first method, the additive penalty method (APM), is a commonly used...

The rate of sorption of 1,2-dichlorobenzene (DCB) onto a natural sandy soil in water-saturated soil columns was measured. Desorption rates were also measured after allowing the solute-sorbent system to equilibrate during a no-flow period, ranging from 3 to 49 d. Two-site equilibrium/kinetic and Γ-distributed rate sorption models were then used to d...

Rate-limited sorption and desorption strongly influence the fate, transport, and remediation of organic pollutants in subsurface environments. In this study, the rates of sorption and desorption were quantified for 1,2-dichlorobenzene to and from five natural sorbents using a batch methodology. Solute/sorbent contact times of 3, 7, 14, 49, and 99 d...

Genetic algorithm optimization of pump-and-treat ground water remediation is used to explore the extent of bias introduced into remediation designs and costs by sorption assumptions. Remediation problems with equilibrium sorption and two-site kinetic sorption with different mass transfer rates are addressed. Under the time-scales and flow condition...

Typically in optimal groundwater remediation design, the objective is to minimize the cost of remediation while meeting the water quality constraints by the end of the remediation period. Given that many common groundwater contaminants are hazardous at very low concentrations, even a small violation of the water quality may be the difference betwee...

Objective functions to describe the operating and capital costs of granular activated carbon (GAC) treatment are incorporated into a management model for dynamic optimal pump-and-treat groundwater remediation design. The optimization approach, quasi-Newton differential dynamic programming including a constant shift in the Hessian Matrix, could not...

Simulation models for the fate and transport of groundwater contaminants are important tools for testing our understanding of transport phenomena at long-term contaminated sites and for designing remedial action plans. A finite difference formulation for contaminant transport including a distribution of contaminant mass-transfer rates between the w...

A dynamic optimal control algorithm for ground-water remediation was extended to incorporate treatment facility capital costs, as a function of the peak operating rate. Our approach to including the capital costs of treatment required no additional control variables and only a single additional state variable. Incorporation of the capital costs of...

Differential dynamic programming with quasi-Newton approximation (QNDDP) is combined with a finite element groundwater quality simulation model to determine optimal time-varying pumping policies for reclamation of a contaminated aquifer. The purpose of the QNDDP model is to significantly reduce the large computational effort associated with calcula...

Vapor-phase transport of organic pollutants is one of the important pathways in the distribution and attenuation of volatile organic compounds in the vadose zone. In this study, the impact of vapor-phase partitioning and of the physical-chemical properties of organic pollutants on vapor-phase transport was assessed. An experimentally derived relati...

A successive approximation linear quadratic regulator (SALQR) method with management periods is combined with a finite element groundwater flow and transport simulation model to determine optimal time-varying groundwater pump-and-treat reclamation policies. Management periods are groups of simulation time steps during which the pumping policy remai...

A flexible finite element transport model, which includes the impact of vapor sorption, is developed to simulate the movement of volatile organic compounds (VOCs) in variably saturated porous media. The two-dimensional numerical model predicts contaminant transport by aqueous advection, aqueous dispersion, aqueous and vapor diffusion, and surface v...

Several modifications of the linear-quadratic regulator (LQR) optimization algorithm are developed, and the computational efficiency of each algorithm with respect to groundwater remediation is evaluated. In each case, the optimization model is combined with a finite element groundwater flow and transport simulation model to determine the optimal t...

Unsaturated zone models incorporating the impact of vapor-phase sorption on transport of volatile organic compounds are presented with closed form solutions for one- and two-dimensional cases. In addition to vapor-phase sorption the models incorporate liquid-phase sorption, liquid advection, gaseous diffusion, and volatilization into soil air space...

We conducted laboratory experiments in the summers of 1986 and 1987 to examine the effects of Daphnia pulex body size and ration level on growth of age-0 yellow perch Perca flavescens. Daphnia pulex rations were set at 25 and 40% of yellow perch dry weight. Specific growth rate tended to be higher for smaller fish and decreased with fish size at bo...

Many watershed modeling studies are being conducted to develop Total Maximum Daily Load (TMDL) levels and corresponding management plans for watersheds with surface water impairments. While sufficient water quality information may exist for the regulatory agency to classify a watershed as water quality impaired, these systems may be highly data-lim...

Thesis (M.S.)--Cornell University, Jan., 1989. Bibliography: leaves 129-135.