Impact of Clear Air Act Regulations on Nitrogen Fate and Transport in the Neuse River Basin

2012 S.C. Water Resources Conference - Exploring Opportunities for Collaborative Water Research, Policy and Managemen

The environmental fate, transformation, and speciation of nano copper oxide in a freshwater environment

The use and production of engineered nanomaterials have grown rapidly over the past few decades due to their unique properties and versatility. As a result of widespread industrial applications, nanomaterials have evolved into their own unique class of emerging contaminants. However, the full extent of nanomaterials’ impact on the environment is currently unknown. In this study, we use the Water Quality Analysis Simulation Program (WASP, version 8.32) to investigate the fate, transformation, and speciation of nano copper oxide (nanoCuO), a common component of antifouling boat-bottom paints, in a freshwater environment over the course of 101 years. WASP serves as a powerful modeling framework that allows users to create dynamic, mechanistic water quality models. WASP’s recently upgraded Advanced Toxicant module allows for novel investigations of nanomaterials, including the parameterization of heteroaggregation and dissolution processes. To our knowledge, our study is the first to use WASP to investigate the fate and transport of any copper-based nanomaterial. In addition to nanoCuO, we also modeled the byproduct of its dissolution (ionic copper, Cu2+), which is of particular interest to regulatory agencies due to its well-known toxic effects on aquatic organisms. Using WASP, we modeled the variables, including dissolved organic carbon and suspended particulate matter, and processes governing the behavior of both nanoCuO and Cu2+ once released to the surface waters and sediments of Lake Waccamaw, North Carolina from boats coated with nanoCuO bottom paint. We also simulated water temperature to investigate the effects that temperature has on the behavior of nanoCuO and Cu2+. After 101 years, we found the highest nanoCuO and Cu2+ accumulation in Lake Waccamaw’s surface sediments, reaching total concentrations of 4.9 mg Cu/kg and 1.3 mg Cu/kg, respectively. Our results may benefit research efforts to predict the toxicity of nanoCuO used widely in aquatic systems

Using a Multimedia Modeling Approach to Simulate Eutrophication in the Pawcatuck River Estuary

The Pawcatuck River Estuary (PRE), composed of the Pawcatuck River and Little Narragansett Bay (CT/RI, USA), is a coastal plain estuary subject to environmental stress. Anthropogenic nutrient loading, watershed land use changes, and urbanization have contributed to eutrophication, which results in hypoxia and seagrass loss. To understand these processes, a one-dimensional, numerical, process-based model was developed to interpret and predict spatial variations in water quality, using WASP8 (Water Analysis Simulation Program, v 8.32). Our PRE WASP Model included five different sub-modules: Dynamic Wave, or DYNHYD5, was used for hydrodynamics, the heat module for water temperature, the advanced eutrophication module for water quality and biological components, and the sediment diagenesis module for sediment oxygen demand and benthic nutrient exchanges. A Hydrological Simulation Program - FORTRAN (HSPF) model, developed by RESPEC (2022), modeled the Wood-Pawcatuck watershed to provide upstream boundary inputs and watershed loads. The multimedia modeling approach created a WASP model which represented hydrodynamics and water quality. The combination of the modeling effort and analysis of observed data demonstrated the presence of a salinity wedge reaching further upstream than originally anticipated. The model captured decreases in dissolved oxygen (DO) and increases in phytoplankton (chlorophyll a) moving upstream. The simulation of macroalgae confirmed nutrient depletion and shading in Little Narragansett Bay. Due to the constraints of the one-dimensional model, the observed, vertical DO gradient was not captured. Our findings also emphasize the importance of the salt wedge and impact of sediment oxygen demand on hypoxia in benthic waters. These insights will be used to support management efforts and total maximum daily load (TMDL) development for ecosystem restoration. Further research will include exploring trade-offs of expanding into two- and three-dimensions using Environmental Fluid Dynamics Code (EFDC), as well as simulating the impact of climate change scenarios and ocean acidification

A Survey of Precipitation Data for Environmental Modeling

There is always a challenge of obtaining the “best” data to inform environmental models. Here we present different types of available precipitation datasets while detailing temporal and spatial resolution, potential errors in the dataset, and optimal performance scenarios. Our goal is to inform modelers of the various types, resolutions, and sources of precipitation data available for environmental modeling. Precipitation is the main driver in the hydrological cycle and modelers use this information to understand water quality and water availability. Environmental models use observed precipitation information for modeling past or current conditions, while simulated data are used to predict future conditions as well as recreate historic conditions. Several precipitation datasets and data generation methods such as National Climatic Data Center (NCDC) rain gauges, National and Global Land Data Assimilation (NLDAS, GLDAS), Next Generation Weather Radar, and Stochastic Weather Generators are described, giving their strengths and weaknesses. USEPA’s Hydrologic Micro Services (HMS) project has developed a collection of interoperable water quantity and quality modeling components that leverage existing internet-based data sources and sensors via a web service. The precipitation component of USEPA’s Hydrologic Micro Service (HMS) will provide the information and data from multiple sources through the web service for modeling purposes

An Overview of Rainfall-Runoff Model Types

This paper aims to inform the audience of the strengths and weaknesses of various rainfall-runoff models. Runoff plays an important role in the hydrological cycle by returning excess precipitation to the oceans and controlling how much water flows into water systems. Water resource managers use runoff data from models to help understand, control, and monitor the quality and quantity of water resources. Access to runoff data can be time consuming and restrictive. The goal of the USEPA’s Hydrologic Micro Service (HMS) project is to develop a collection of interoperable water quantity and quality modeling components that leverage existing internet-based data sources and sensors via a web service. Each component may have multiple implementations, ranging from coarse to detailed levels of physical process modeling. Each rainfall-runoff model contains algorithms that control the calculation of runoff. Models can be categorized by the structure and spatial processing of these algorithms into empirical, conceptual, physical, lumped, semi-distributed, and distributed models. Several runoff models, including SCS Curve Number, Hydrological Simulation Program-Fortran, and Penn State’s Integrated Hydrological Modeling System, are described, providing information to determine which best suits the modeling objective

Urban Stream Burial Increases Watershed-Scale Nitrate Export

Nitrogen (N) uptake in streams is an important ecosystem service that reduces nutrient loading to downstream ecosystems. Here we synthesize studies that investigated the effects of urban stream burial on N-uptake in two metropolitan areas and use simulation modeling to scale our measurements to the broader watershed scale. We report that nitrate travels on average 18 times farther downstream in buried than in open streams before being removed from the water column, indicating that burial substantially reduces N uptake in streams. Simulation modeling suggests that as burial expands throughout a river network, N uptake rates increase in the remaining open reaches which somewhat offsets reduced N uptake in buried reaches. This is particularly true at low levels of stream burial. At higher levels of stream burial, however, open reaches become rare and cumulative N uptake across all open reaches in the watershed rapidly declines. As a result, watershed-scale N export increases slowly at low levels of stream burial, after which increases in export become more pronounced. Stream burial in the lower, more urbanized portions of the watershed had a greater effect on N export than an equivalent amount of stream burial in the upper watershed. We suggest that stream daylighting (i.e., uncovering buried streams) can increase watershed-scale N retention

Poster Abstract: Effects of precipitation data source selection on SWAT hydrologic simulation

Precipitation is one of the major inputs for hydrological modeling and often it is the most important driver in watershed models. Even though precipitation measurements at gages are considered as the most accurate datasets, gages are unable to capture the spatial and temporal variability of precipitation. Interpolated gridded precipitation data sources have become increasingly available as alternatives to ground based measurements that address spatiotemporal issues. However, the use of gridded precipitation sources is limited, mainly due to mismatch of these gridded data to the requirements of models and difficulty in processing. This study uses the U.S. EPA Hydrologic Micro Services (HMS) infrastructure to acquire and process precipitation inputs for Soil and Water Assessment Tool (SWAT) from Daily Surface Weather Data (DAYMET), North American Land Data Assimilation System (NLDAS), Global Land Data Assimilation System (GLDAS), and Precipitation-elevation Regressions on Independent Slopes Model (PRISM). Global Historical Climate Network-Daily (GHCN-D), an integrated database of daily climate summaries from ground-based stations across the globe, was used as reference data to evaluate how closely the gridded data represent precipitation. SWAT was used to identify the effects of different sources on hydrological processes in an agricultural catchment. The preliminary results indicated that there were considerable differences among GHCN-D (the observed data) and the gridded data in terms of number and consecutive wet and dry days. PRISM and DAYMET closely matched GHCN-D in those indices, while NLDAS and GLDAS showed much weaker correlations with GHCN-D. Similar differences were also observed for SWAT streamflow simulations

Simulating Toxicant Concentrations in Surface Waters and Sediments: Advances in the Water Quality Analysis Simulation Program (WASP8)

Toxicant concentrations in surface waters and sediments are of environmental concern due to their potential impacts on ecological and human receptors. Numerical, process-based, mass balance models are one way to understand a system and its governing processes, assist in supporting management decisions, and evaluate different toxicant release scenarios. The US Environmental Protection Agency has developed and continues to improve the Water Quality Analysis Simulation Program (WASP), which is one of the more widely used water quality models in the US and the world. WASP is a modeling framework with which the user can develop a water quality model for nutrients or toxicants over a range of complexities and temporal and spatial scales. With the release of WASP version 8, the architecture of the toxicant module has been updated to allow for an increased number of state variables, including chemical solutes, particulates, and nanomaterials; as well explicitly simulating pathogens, temperature, different classes of dissolved organic carbon, and salinity. This presentation will focus on the recent developments, including the revised WASP8 structure and interface and the advances in simulating different classes of toxicants in surface waters and sediments. Details will be given on the new structure for handling light intensity in stream segments, including the distinction of different wavelengths of light, and on simulating nanomaterials, different particle attachment processes, and handling the transformation and production of one state variable to another. A WASP8 example is presented for simulating chemical, nanomaterial, and solid concentrations in the Cape Fear River, North Carolina, USA

Hydrologic Micro Services (HMS) Architecture

An often encountered issue in hydrological and water quality modeling is matching the problem statement with available model(s). Workflows can consist of a single model or be composed by linking multiple models to address the problem statement. This often requires custom-written software wrappers and/or the use of modeling frameworks. Modelers often spend significant amounts of time parameterizing the selected model(s) because many were developed before access to environmental databases were available online. The entire model may have to be used even if the problem statement requires only a subset of the its functionality. Individual models may not simulate all the physical processes to the detail level required by the problem statement, or may not simulate all the desired water quality constituents, leaving the modeler to simulate proxy constituent(s). A componentized system, Hydrologic Micro Services (HMS), is being developed to address these issues. The HMS architecture contains a collection of inter-operable data and modeling services. The water quantity and quality components can be used to construct workflows tailored to specific problem statements. The primary design objective of HMS is to make the components available as RESTful web services, as well as desktop libraries, so they can be easily integrated within complex workflows. Each component may have multiple implementations ranging from macro (coarse) to micro (detailed) that will allow users to choose the appropriate level of detail for the problem statement