James L. Martin

Hydrodynamic Modeling of First-Order Transport Timescales in the St. Louis Bay Estuary, Mississippi

AbstractThe transport timescales residence time, exposure time, and age of water are evaluated for the St. Louis Bay estuary, Mississippi, to investigate the impacts of freshwater inflows and tidal dynamics from Mississippi Sound on the estuary’s transport characteristics. The timescales are explicitly defined and computed using a hydrodynamic model and tracer experiments for a set of 11 hydrologic scenarios designed to represent permanent low, average, and high flow conditions. Results indicate that (1) the estuary’s residence time can vary between 2.0 and 134.5 days during high and low flow conditions, respectively; (2) under low flow conditions dispersive processes caused by the tidal dynamics at the estuary’s open boundary may be dominant, and the returning flows can increase the exposure times up to 30% in relation to the residence times; (3) during high flow conditions advective transport caused by the freshwater flows may be dominant resulting in exposure times similar to the residence times; and, ...

Modeling the Factors Controlling Phytoplankton in the St. Louis Bay Estuary, Mississippi and Evaluating Estuarine Responses to Nutrient Load Modifications

AbstractSeveral biochemical and physical factors regulate phytoplankton primary productivity and algal bloom events in estuarine environments. Some of the most important factors include nitrogen, phosphorus and silica availability, light availability, and estuarine flushing potential. A better understanding of these processes is necessary to support sound management strategies that take into account the hydrological, hydraulic, and biochemical connectivity between estuaries and their watersheds. In this paper the factors controlling phytoplankton productivity in a tributary estuary of the northern Gulf of Mexico, the St. Louis Bay estuary, Mississippi, and the system responses to nutrient load alterations are studied. For this purpose a coupled hydrodynamic and water quality model based on U.S. EPA computer models was implemented. The writers present an evaluation of the model predictive capacity, and its implementation to study the processes controlling phytoplankton dynamics, nutrient cycling, and oxyge...

Analysis of Hydrological Processes Applying the HSPF Model in Selected Watersheds in Alabama, Mississippi, and Puerto Rico

The goal of this study was to evaluate the Hydrological Simulation Program – FORTRAN (HSPF) to gain more insight in the underlying causes and mechanisms of hydrological processes in an upland basin in Alabama and Mississippi (1,856-km2 Luxapallila Creek), a humid subtropical watershed in coastal Alabama (140-km2 Fish River), and a steep-slope tropical catchment in Puerto Rico (99-km2 Rio Caonillas). For each watershed model, rainfall, potential evapotranspiration, and streamflow time series from January 1999 to December 2000 were used to calibrate model parameters and 2001 time series were applied to verify model results. In each study area, actual evapotranspiration was the main mechanism of water loss followed by river discharge. Annual baseflow values ranged from 58% of total discharge in Luxapallila Creek basin to 84% of total discharge in Fish River watershed. In Luxapallila Creek and Fish River, interflow was the primary mechanism of direct runoff; however, surface runoff was the main process of direct runoff in Rio Caonillas. The HSPF model was successfully adapted to model daily streamflow processes in Luxapallila Creek basin and Rio Caonillas catchment with coefficient of determination and Nash and Sutcliffe coefficient values between 0.61 and 0.71 for the entire period; however, the Fish River watershed model performance was poor. The poor performance is likely due to the lack of rainfall time series available within the watershed boundaries. In general, this study showed the robustness of the HSPF model in extreme environments (small catchments vs. large basins, flat vs. hilly areas, low vs. moderate/high runoff potential, tropical marine vs. humid subtropical climates).

In-stream hydrokinetic power: Review and appraisal

AbstractThe objective of this paper is to provide a review of in-stream hydrokinetic power, which is defined as electric power generated by devices capturing the energy of naturally flowing water—stream, tidal, or open ocean flows—without impounding the water. North America has significant in-stream energy resources, and hydrokinetic electric power technologies to harness those resources have the potential to make a significant contribution to U.S. electricity needs by adding as much as 120  TWh/year from rivers alone to the present hydroelectric power generation capacity. Additionally, tidal and ocean current resources in the U.S. respectively contain 438  TWh/year and 163  TWh/year of extractable power. Among their attractive features, in-stream hydrokinetic operations do not contribute to greenhouse gas emissions or other air pollution and have less visual impact than wind turbines. Since these systems do no utilize dams the way traditional hydropower systems typically do, their impact on the environme...

Temperature and Conductivity Modeling for the Buffalo River

Abstract A hydrodynamic and water quality transport study of the Buffalo River has been conducted. Using a two-dimensional (laterally averaged) model and with appropriate specification of boundary conditions, the transport of river water temperature and conductivity has been simulated for the period of June-August, 1988. The model results are compared with measurements both for temperature and conductivity. Stratification patterns are well described by the model. The results also suggest that heat flux through the water surface is primarily responsible for the stratification during the heating process in the summer. The simulated conductivity compares well with the measurement for most situations but underestimates in regions close to the mouth. Such discrepancies are attributed to neglecting point and non-point source loadings in the simulation.

IMPACTS OF LAND USE CHARACTERIZATION IN MODELING HYDROLOGY AND SEDIMENTS FOR THE LUXAPALLILA CREEK WATERSHED, ALABAMA AND MISSISSIPPI

The Hydrological Simulation Program - Fortran (HSPF), interfaced with the Better Assessment Science Integrating Point and Nonpoint (BASINS), was used to evaluate the impact of land use (as characterized by different land use/land cover (LU/LC) datasets) on hydrology and sediment components of the Luxapallila Creek watershed. The 1,770 km2 watershed is located in Alabama and Mississippi. Simulation of the watershed processes were tested at the hillslope and at the watershed outlet for the period between 1985 and 2003. Three LU/LC databases were used: the Geographic Information Retrieval and Analysis System (GIRAS), the Moderate Resolution Imaging Spectroradiometer land cover product (MODIS MOD12Q1), and the National Land Cover Dataset (NLCD). The two main land use categories revealed by the three LU/LC databases were forest and agricultural lands. Whereas forest cover mechanisms were the main source of water loss in hydrology simulation, agricultural land was the main source of sediment export in sediment modeling. Land use datasets of coarser spatial resolution (MODIS and GIRAS) produced larger HSPF estimations for sediment fraction values than land use datasets identifying smaller percentages of those agricultural land cover classes (NLCD). Differences in agricultural land characterization among the land use datasets showed that sediment predictions were more sensitive than streamflow predictions to the scale and resolution of land use datasets. Choosing the right land use dataset will impact the modeling of sediments and, potentially, other water quality constituents that are related with agricultural activities.

A Comparison of Bayesian Methods for Uncertainty Analysis in Hydraulic and Hydrodynamic Modeling

We evaluate and compare the performance of Bayesian Monte Carlo (BMC), Markov chain Monte Carlo (MCMC), and the Generalized Likelihood Uncertainty Estimation (GLUE) for uncertainty analysis in hydraulic and hydrodynamic modeling (HHM) studies. The methods are evaluated in a synthetic 1D wave routing exercise based on the diffusion wave model, and in a multidimensional hydrodynamic study based on the Environmental Fluid Dynamics Code to simulate estuarine circulation processes in Weeks Bay, Alabama. Results show that BMC and MCMC provide similar estimates of uncertainty. The posterior parameter densities computed by both methods are highly consistent, as well as the calibrated parameter estimates and uncertainty bounds. Although some studies suggest that MCMC is more efficient than BMC, our results did not show a clear difference between the performance of the two methods. This seems to be due to the low number of model parameters typically involved in HHM studies, and the use of the same likelihood function. In fact, for these studies, the implementation of BMC results simpler and provides similar results to MCMC. The results of GLUE are, on the other hand, less consistent to the results of BMC and MCMC in both applications. The posterior probability densities tend to be flat and similar to the uniform priors, which can result in calibrated parameter estimates centered in the parametric space.

A Hydrological Model of the Mobile River Watershed, Southeastern USA

A hydrological model of the Mobile Bay watershed located in the northern Gulf of Mexico, (Alabama, USA) is presented. The modeling of hydrological processes is performed using the Hydrological Simulation Program Fortran (HSPF). The project region was divided into two sectors for simplifying the modeling task: an upland watershed (that included streams not draining directly to the Mobile Estuary), and several watersheds of selected streams that drain directly to the Mobile estuary (namely: Fish River, Magnolia River, and Chickasaw Creek). The Better Assessment Science Integrating Point & Nonpoint Sources (BASINS) GIS system was used to perform most of the geospatial operations, although ArcGis and ArcInfo were also used to complement geospatial processing that was not available in BASINS.

Wetlands for Wastewater Treatment.

This paper provides a review of the treatment technologies, which utilize natural processes or passive components in wastewater treatment. In particular, this paper primarily focuses on wetland systems and their applications in wastewater treatment (as an advanced treatment unit or decentralized system), nutrient and pollutant removal (single and multiple pollutants, and metals), and emerging pollutant removal (pharmaceuticals). A summary of studies involving the plant (vegetation) effects, wetland design and modeling, hybrid and innovative systems, storm water treatment and pathogen removal is also included.

Estimation and Propagation of Parameter Uncertainty in Lumped Hydrological Models: A Case Study of HSPF Model Applied to Luxapallila Creek Watershed in Southeast USA

Estimation and Propagation of Parameter Uncertainty in Lumped Hydrological Models: A Case Study of HSPF Model Applied to Luxapallila Creek Watershed in Southeast USA Explicit quantification of the uncertainty associated to the predictions of a hydrologic model is a necessary activity to objectively evaluate and report the limitations of the model caused by different sources of error. The current state of the practice of hydrologic modeling indicates that parametric uncertainty is considered as one of the most important sources of uncertainty. Some of the most relevant problems remaining in the practice include the identification of the principal parameters affecting model predictions and quantification of parameter ranges. This study evaluated stochastically one of the most popular deterministic watershed water quality models for decision making in USA.