Download or read book Water Quality Conditions in Chesapeake Bay Using Model Results written by Arthur J. Butt and published by . This book was released on 1993 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Using Water Quality Models in Management a Multiple Model Assessment Analysis of Confidence and Evaluation of Climate Change Impacts written by Issac David Irby and published by . This book was released on 2017 with total page 193 pages. Available in PDF, EPUB and Kindle. Book excerpt: Human impacts on the Chesapeake Bay through increased nutrient run-off as a result of land-use change, urbanization, and industrialization, have resulted in a degradation of water quality over the last half-century. These direct impacts, compounded with human-induced climate changes such as warming, rising sea-level, and changes in precipitation, have elevated the conversation surrounding the future of water quality in the Bay. The overall goal of this dissertation project is to use a combination of models and data to better understand and quantify the impact of changes in nutrient loads and climate on water quality in the Chesapeake Bay. This research achieves that goal in three parts. First, a set of eight water quality models is used to establish a model mean and assess model skill. All models were found to exhibit similar skill in resolving dissolved oxygen concentrations as well as a number of dissolved oxygen-influencing variables (temperature, salinity, stratification, chlorophyll and nitrate) and the model mean exhibited the highest individual skill. The location of stratification within the water column was found to be a limiting factor in the models’ ability to adequately simulate habitat compression resulting from low-oxygen conditions. Second, two of the previous models underwent the regulatory Chesapeake Bay pollution diet mandated by the Environmental Protection Agency. Both models exhibited a similar relative improvement in dissolved oxygen concentrations as a result of the reduction of nutrients stipulated in the pollution diet. A Confidence Index was developed to identify the locations of the Bay where the models are in agreement and disagreement regarding the impacts of the pollution diet. The models were least certain in the deep part of the upper main stem of the Bay and the uncertainty primarily stemmed from the post-processing methodology. Finally, by projecting the impacts of climate change in 2050 on the Bay, the potential success of the pollution diet in light of future projections for air temperature, sea level, and precipitation was examined. While a changing climate will reduce the ability of the nutrient reduction to improve oxygen concentrations, that effect is trumped by the improvements in dissolved oxygen stemming from the pollution diet itself. However, climate change still has the potential to cause the current level of nutrient reduction to be inadequate. This is primarily due to the fact that low-oxygen conditions are predicted to start one week earlier, on average, in the future, with the primary changes resulting from the increase in temperature. Overall, this research lends an increased degree of confidence in the water quality modeling of the potential impact of the Chesapeake Bay pollution diet. This research also establishes the efficacy of utilizing a multiple model approach to examining projected changes in water quality while establishing that the pollution diet trumps the impact from climate change. This work will lead directly to advances in scientific understanding of the response of water quality, ecosystem health, and ecological resilience to the impacts of nutrient reduction and climate change.

Download or read book Water Quality Conditions in the Chesapeake Bay System written by Thomas H. Pheiffer and published by . This book was released on 1972 with total page 346 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Toward A Comprehensive Water Quality Model For The Chesapeake Bay Using Unstructured Grids written by Xun Cai and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chesapeake Bay is one of the most productive ecosystems on the US east coast which supports various living resources and habitat, and therefore has significant impacts on human beings and ecosystem health. Developing the capability of accurately simulating the water quality condition in the Chesapeake Bay, such as seasonal hypoxia, phytoplankton production, and nutrient dynamics, helps to better understand the interactions of hydrodynamical and biochemical processes, and more importantly, to predict conditions under changing climate and human intervention. Currently, most Chesapeake Bay models use structured grids that lack the flexibility for local refinements to fit complex geometry over both large and small scales, which hampers the allocation of local TMDLs for shallow water and small tributaries. In addition, few of them extend their simulations beyond the water column state variables, such as dissolved oxygen and nutrients, to include other living resources such as vegetation. These limitations motivate the model developments in this dissertation of: (1) a new comprehensive water quality model using high-resolution unstructured grids, which possesses the cross-scale capability to study interactions among water bodies and processes of different scales; and (2) a tightly coupled tidal marsh model, which is linked to the water quality model for water column to study the interactions between the marshes and surrounding aquatic system. The new modeling tool can be effectively utilized as a powerful tool for adaptive management in the Chesapeake Bay and can also be exported to other estuaries in the world.In this dissertation, Chapter 2 focuses on the development of a high-resolution water quality model in the water column and sediment flux part of the water quality model. This part of this study also demonstrates the importance of the correct representation of geometry, and the detrimental effects of artificial bathymetry smoothing on model simulations. Chapter 3 of this dissertation studies the impacts of sea-level rise (SLR) on seasonal hypoxia and phytoplankton production in the Chesapeake Bay with the newly developed water quality model. SLR is predicted to increase the hypoxic volume in the Chesapeake Bay by altering the physical processes and enhancing the estuarine respirations. Phytoplankton production in the shallow shoals is also predicted to increase under SLR, as a result of increased light utilization. Chapter 4 of this dissertation focuses on developing a new marsh model in the hydrodynamic-water quality model framework. This new model extends the model coverage to the tidal wetlands which are periodically inundated. The tidal marshes are suggested to affect the estuarine oxygen, carbon, and nutrient dynamics through tidal exchange, e.g., contributing the diel DO cycle. Chapter 5 studies the impacts of SLR on the biochemical processes in the York River Estuary, a tributary of the Bay that has extensive tidal marshes, with the fully-coupled hydrodynamic-water quality-marsh model. The SLR is predicted to enhance the exchanges between the marshes and the adjacent channel, which in turn further impacts the estuarine biochemical processes.

Download or read book Integrated Analysis of Chesapeake Bay Monitoring Data written by and published by . This book was released on 1998 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Chesapeake Bay Water Quality Modeling written by Virginia. State Water Control Board. Chesapeake Bay Office and published by . This book was released on 1991 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Achieving Nutrient and Sediment Reduction Goals in the Chesapeake Bay written by National Research Council and published by National Academies Press. This book was released on 2011-09-26 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Chesapeake Bay is North America's largest and most biologically diverse estuary, as well as an important commercial and recreational resource. However, excessive amounts of nitrogen, phosphorus, and sediment from human activities and land development have disrupted the ecosystem, causing harmful algae blooms, degraded habitats, and diminished populations of many species of fish and shellfish. In 1983, the Chesapeake Bay Program (CBP) was established, based on a cooperative partnership among the U.S. Environmental Protection Agency (EPA), the state of Maryland, and the commonwealths of Pennsylvania and Virginia, and the District of Columbia, to address the extent, complexity, and sources of pollutants entering the Bay. In 2008, the CBP launched a series of initiatives to increase the transparency of the program and heighten its accountability and in 2009 an executive order injected new energy into the restoration. In addition, as part of the effect to improve the pace of progress and increase accountability in the Bay restoration, a two-year milestone strategy was introduced aimed at reducing overall pollution in the Bay by focusing on incremental, short-term commitments from each of the Bay jurisdictions. The National Research Council (NRC) established the Committee on the Evaluation of Chesapeake Bay Program Implementation for Nutrient Reduction in Improve Water Quality in 2009 in response to a request from the EPA. The committee was charged to assess the framework used by the states and the CBP for tracking nutrient and sediment control practices that are implemented in the Chesapeake Bay watershed and to evaluate the two-year milestone strategy. The committee was also to assess existing adaptive management strategies and to recommend improvements that could help CBP to meet its nutrient and sediment reduction goals. The committee did not attempt to identify every possible strategy that could be implemented but instead focused on approaches that are not being implemented to their full potential or that may have substantial, unrealized potential in the Bay watershed. Because many of these strategies have policy or societal implications that could not be fully evaluated by the committee, the strategies are not prioritized but are offered to encourage further consideration and exploration among the CBP partners and stakeholders.

Download or read book Water Quality Conditions in Chesapeake Bay System written by and published by . This book was released on 1972 with total page 343 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Technical Analysis of Response of Chesapeake Bay Water Quality Model to Loading Scenarios written by and published by . This book was released on 1994 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Chesapeake Bay Watershed Model Application and Calculation of Nutrient and Sediment Loadings written by Gary W. Shenk and published by . This book was released on 1998 with total page 641 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Modeling the Impacts of Climate Variability and Change on Circulation and Salinity in Chesapeake and Delaware Bays written by Andrew Ross and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation discusses the use of numerical models to simulate the effects of climate variability and change on Chesapeake and Delaware Bays, two large coastal plain estuaries in the Mid-Atlantic Region of the United States that are both home to productive ecosystems, important ports, and large concentrations of human population. Estuaries like these bays are uniquely characterized by salinity variation from riverine freshwater to oceanic saltwater, both horizontally and vertically, and by the strength of their tides. From a meteorological perspective, estuaries are interesting because they are influenced by many aspects ofweather and climate variability, including runoff and winds. Future climate changes, including changesin river discharge and mean sea level, are also likely to produce significant changes in estuarine salinity and circulation and could alter estuarine ecosystems. To predict the effects these changes may haveon estuarine salinity, circulation, and ecosystems, numerical model simulations are often applied.However, the predictive capability of numerical models is unknown due in part to a lack of knowledge about historical trends and whether numerical models can reproduce them. This dissertation is composed of three studies that address this lack of knowledge. The first study of this dissertation analyzes data from tide gauges in Chesapeake and Delaware Bays and compares the results with model simulations to determine what trends are present and whether the numerical model correctly predicts these trends. When using the numerical model for predictions, it is also important to account for uncertainty in the model and its inputs, but doing so is difficult due to the chain of computationally expensive models typically used to simulate estuaries. The second study of this dissertation examines a method to account for uncertainty in future river discharge, and the third study conducts an analysis of which inputs the numerical model is most sensitive to.In the first study, statistical models show negative M2 amplitude trends at the mouths of both bays, while some upstream locations have insignificant or positive trends. To determine whether sea-level rise isresponsible for these trends, a term for mean sea level is included in the statistical models and the results are compared with with predictions from numerical and analytical models. The observed and predicted sensitivities of M2 amplitude and phase to mean sea level are similar, although the numerical model amplitude is less sensitive to sea level. The sensitivity occurs as a result of strengthening and shifting of the amphidromic system in the Chesapeake Bay and decreasing frictional effects and increasing convergence in the Delaware Bay. After accounting for the effect of sea level, significant negative background M2 and S2 amplitude trends are present; these trends may be related to other factors such as dredging, tide gauge errors, or river discharge. Projected changes in tidal amplitudes due to sea-level rise over the twenty-first century are substantial in some areas, but depend significantly on modeling assumptions.The second study examines the impacts of methods for model selection on projections of runoff change for the Susquehanna River Basin. The results from an ensemble of 29 global climate models and 29 corresponding hydrological model simulations were compared with the results that would have been obtained by applying five different selection strategies to the climate model data and using only the selected models to drive the hydrological model. Only one method, the KKZ algorithm, produced results that met the objective of the method and were not strongly sensitive to the number of models selected. Regardless of the selection method used, the results for small model subsets (fewer than about 7 models) were highly variable and failed to cover the uncertainty present in the full model dataset. On the other hand, results from the complete model ensemble may be affected by structurally and statistically similar models. This study shows that the methods and models used in similar top-down studies should be carefully chosen and that the results obtained should be interpreted with caution.Finally, estuarine physics and water quality are strongly controlled by climate and oceanographic variability.Climate and oceanographic conditions are likely to change in the future as a result of global climate change, and it is important to consider how these changes, and how uncertainty surrounding these changes,could affect water quality and management. To do so, numerical models are typically used to simulate estuarine physics and water quality under scenarios of future conditions. However, the numerical models typically used for simulating estuaries are computationally demanding, limiting the ability to understand and quantify uncertainty in the model results. In the third study of this dissertation, a computationally inexpensive statistical model, or metamodel, is tested as a surrogate for numerical model simulations. The metamodel is fit to 12 numerical model simulations of the Chesapeake Bay and used to simulate stratification, circulation, and mean salinity under sampled probability distributions of projected future mean sea level, river discharge, and tidal amplitudes along the shelf. The simulations from the metamodel show that future salinity, stratification, and circulation are all likely to be higher than present-day averages. However, the metamodel indicates that model projections of salinity and stratification are highly sensitive to uncertainty about future tidal amplitudes along the shelf. Since previous studies have focused on potential changes in either river discharge or sea level while neglecting any change in tidal amplitude, these results demonstrate the importance of conducting a thorough sensitivity and uncertainty analysis. Future studies should build from this concept by including more sources of uncertainty, such as wind speed and direction and model parameters and structures.The results in this dissertation show that although numerical models are capable of reproducing some past changes, the impacts of future climate and oceanographic changes on these estuaries remain highly uncertain. Salinity and stratification in the Chesapeake Bay are fairly likely to increase as a result of a highly probable increase in mean sea level, although exact changes are especially sensitive to changes in tidal amplitude. Model simulations of future tides in both bays appear to be sensitive to the methods used to model sea-level rise even though the simulations of past tides in this dissertation are not. In future work, it will be important to consider this uncertainty, to consider other uncertainties that were neglected in this dissertation, and to examine the impacts on biogeochemistry and overall ecosystem health.

Download or read book Hydrodynamics and Transport for Water Quality Modeling written by James L. Martin and published by CRC Press. This book was released on 1998-12-15 with total page 820 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydrodynamics and Transport for Water Quality Modeling presents a complete overview of current methods used to describe or predict transport in aquatic systems, with special emphasis on water quality modeling. The book features detailed descriptions of each method, supported by sample applications and case studies drawn from the authors' years of experience in the field. Each chapter examines a variety of modeling approaches, from simple to complex. This unique text/reference offers a wealth of information previously unavailable from a single source. The book begins with an overview of basic principles, and an introduction to the measurement and analysis of flow. The following section focuses on rivers and streams, including model complexity and data requirements, methods for estimating mixing, hydrologic routing methods, and unsteady flow modeling. The third section considers lakes and reservoirs, and discusses stratification and temperature modeling, mixing methods, reservoir routing and water balances, and dynamic modeling using one-, two-, and three-dimensional models. The book concludes with a section on estuaries, containing topics such as origins and classification, tides, mixing methods, tidally averaged estuary models, and dynamic modeling. Over 250 figures support the text. This is a valuable guide for students and practicing modelers who do not have extensive backgrounds in fluid dynamics.

Download or read book Chesapeake Bay Watershed Model Application and Calculation of Nutrient and Sediment Loadings written by and published by . This book was released on 1998 with total page 641 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Sources Fate and Transport of Nitrogen and Phosphorus in the Chesapeake Bay Watershed written by Scott W. Ator and published by Geological Survey (USGS). This book was released on 2011 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: Spatially Referenced Regression on Watershed Attributes (SPARROW) was used to provide empirical estimates of the sources, fate, and transport of total nitrogen (TN) and total phosphorus (TP) in the Chesapeake Bay watershed, and the mean annual TN and TP flux to the bay and in each of 80,579 nontidal tributary stream reaches. Restoration efforts in recent decades have been insufficient to meet established standards for water quality and ecological conditions in Chesapeake Bay. The bay watershed includes 166,000 square kilometers of mixed land uses, multiple nutrient sources, and variable hydrogeologic, soil, and weather conditions, and bay restoration is complicated by the multitude of nutrient sources and complex interacting factors affecting the occurrence, fate, and transport of nitrogen and phosphorus from source areas to streams and the estuary. Effective and efficient nutrient management at the regional scale in support of Chesapeake Bay restoration requires a comprehensive understanding of the sources, fate, and transport of nitrogen and phosphorus in the watershed, which is only available through regional models. The current models, Chesapeake Bay nutrient SPARROW models, version 4 (CBTN_v4 and CBTP_v4), were constructed at a finer spatial resolution than previous SPARROW models for the Chesapeake Bay watershed (versions 1, 2, and 3), and include an updated timeframe and modified sources and other explantory terms.

Download or read book Review of the New York City Watershed Protection Program written by National Academies of Sciences, Engineering, and Medicine and published by National Academies Press. This book was released on 2020-12-04 with total page 423 pages. Available in PDF, EPUB and Kindle. Book excerpt: New York City's municipal water supply system provides about 1 billion gallons of drinking water a day to over 8.5 million people in New York City and about 1 million people living in nearby Westchester, Putnam, Ulster, and Orange counties. The combined water supply system includes 19 reservoirs and three controlled lakes with a total storage capacity of approximately 580 billion gallons. The city's Watershed Protection Program is intended to maintain and enhance the high quality of these surface water sources. Review of the New York City Watershed Protection Program assesses the efficacy and future of New York City's watershed management activities. The report identifies program areas that may require future change or action, including continued efforts to address turbidity and responding to changes in reservoir water quality as a result of climate change.

Download or read book Achieving Nutrient and Sediment Reduction Goals in the Chesapeake Bay written by National Research Council and published by National Academies Press. This book was released on 2011-10-26 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Chesapeake Bay is North America's largest and most biologically diverse estuary, as well as an important commercial and recreational resource. However, excessive amounts of nitrogen, phosphorus, and sediment from human activities and land development have disrupted the ecosystem, causing harmful algae blooms, degraded habitats, and diminished populations of many species of fish and shellfish. In 1983, the Chesapeake Bay Program (CBP) was established, based on a cooperative partnership among the U.S. Environmental Protection Agency (EPA), the state of Maryland, and the commonwealths of Pennsylvania and Virginia, and the District of Columbia, to address the extent, complexity, and sources of pollutants entering the Bay. In 2008, the CBP launched a series of initiatives to increase the transparency of the program and heighten its accountability and in 2009 an executive order injected new energy into the restoration. In addition, as part of the effect to improve the pace of progress and increase accountability in the Bay restoration, a two-year milestone strategy was introduced aimed at reducing overall pollution in the Bay by focusing on incremental, short-term commitments from each of the Bay jurisdictions. The National Research Council (NRC) established the Committee on the Evaluation of Chesapeake Bay Program Implementation for Nutrient Reduction in Improve Water Quality in 2009 in response to a request from the EPA. The committee was charged to assess the framework used by the states and the CBP for tracking nutrient and sediment control practices that are implemented in the Chesapeake Bay watershed and to evaluate the two-year milestone strategy. The committee was also to assess existing adaptive management strategies and to recommend improvements that could help CBP to meet its nutrient and sediment reduction goals. The committee did not attempt to identify every possible strategy that could be implemented but instead focused on approaches that are not being implemented to their full potential or that may have substantial, unrealized potential in the Bay watershed. Because many of these strategies have policy or societal implications that could not be fully evaluated by the committee, the strategies are not prioritized but are offered to encourage further consideration and exploration among the CBP partners and stakeholders.

Download or read book Clean Coastal Waters written by National Research Council and published by National Academies Press. This book was released on 2000-08-17 with total page 422 pages. Available in PDF, EPUB and Kindle. Book excerpt: Environmental problems in coastal ecosystems can sometimes be attributed to excess nutrients flowing from upstream watersheds into estuarine settings. This nutrient over-enrichment can result in toxic algal blooms, shellfish poisoning, coral reef destruction, and other harmful outcomes. All U.S. coasts show signs of nutrient over-enrichment, and scientists predict worsening problems in the years ahead. Clean Coastal Waters explains technical aspects of nutrient over-enrichment and proposes both immediate local action by coastal managers and a longer-term national strategy incorporating policy design, classification of affected sites, law and regulation, coordination, and communication. Highlighting the Gulf of Mexico's "Dead Zone," the Pfiesteria outbreak in a tributary of Chesapeake Bay, and other cases, the book explains how nutrients work in the environment, why nitrogen is important, how enrichment turns into over-enrichment, and why some environments are especially susceptible. Economic as well as ecological impacts are examined. In addressing abatement strategies, the committee discusses the importance of monitoring sites, developing useful models of over-enrichment, and setting water quality goals. The book also reviews voluntary programs, mandatory controls, tax incentives, and other policy options for reducing the flow of nutrients from agricultural operations and other sources.