IberWQ: A GPU Accelerated Tool for 2D Water Quality Modeling in Rivers and Estuaries

Este artigo inclúese no número especial "Modelling Flow, Water Quality, and Sediment Transport Processes in Coastal, Estuarine, and Inland Waters"[Abstract] Numerical models are useful tools to analyze water quality by computing the concentration of physical, chemical and biological parameters. The present work introduces a two-dimensional depth-averaged model that computes the most relevant and frequent parameters used to evaluate water quality. High performance computing (HPC) techniques based on graphic processing unit (GPU) parallelization have been applied to improve the efficiency of the package, providing speed-ups of two orders of magnitude in a standard PC. Several test cases were analyzed to show the capabilities and efficiency of the model to evaluate the environmental status of rivers and non-stratified estuaries. IberWQ will be freely available through the package Iber.European Commission; INTERREG-POCTEP; 0034_RISC_ML_6_EXunta de Galicia; ED431C 2017/64-GRCXunta de Galicia; ED481A-2017/31

Environmental Consequences of a Power Plant Shut-Down: A Three-Dimensional Water Quality Model of Dublin Bay

A hydro-environmental model is used to investigate the effect of cessation of thermal discharges from a power plant on the bathing water quality of Dublin Bay. Before closing down, cooling water from the plant was mixed with sewage effluent prior to its discharge, creating a warmer, less-saline buoyant pollutant plume that adversely affects the water quality of Dublin Bay. The model, calibrated to data from the period prior to the power-plant shut-down (Scenario 1), assessed the water quality following its shut-down under two scenarios; (i) Scenario 2: continued abstraction of water to dilute sewage effluents before discharge, and (ii) Scenario 3: sewage effluents are discharged directly into the Estuary. Comparison between scenarios was based on distribution of Escherichia coli (E. coli), a main bathing quality indicator. Scenarios 1 and 2, showed almost similar E. coli distribution patterns while Scenario 3 displayed significantly higher E. coli concentrations due to the increased stratification caused by the lack of prior dilution

Optimizing the design of an estuarine water quality monitoring network by optimal control techniques

In this work, we propose a novel methodology in order to automatically optimize the location of the sampling points for a water quality monitoring network in an estuary, in such a way that any unknown pollution source can be identified (both in intensity and location) from the data supplied by those sampling points. In the central part of the article, after a rigorous mathematical formulation of the environmental problem, the full details of its numerical implementation are given. Finally, we present and analyze the results when applying the above proposed technique to study a real case in Ría of Vigo (northwestern Spain).Agencia Estatal de Investigación | Ref. TED2021-129324B-I00Universidade de Vigo/CISU

Application of a Hydrodynamic and Water Quality Model for Inland Surface Water Systems

This chapter introduces basic concepts, properties, and principles of different processes in inland surface water and analytical methodologies. The fundamentals of surface water hydrodynamics, including water properties, hydrodynamic processes, Cartesian coordinate-based governing equations, and boundary and initial conditions were reviewed. The fate and transport of contaminants in surface water were introduced. Based on aforementioned theory and principles, two hydrodynamic-water quality models were developed for studying a lake and a river, respectively. A stratified 3D model was used to investigate the circulation and E. coli transport in the nearshore region of Lake Michigan. The modeling results show that stratified phenomenon exists in the near region, and a 3D model is necessary even though a previous 2D model works well for the shallow water environment. A 2D depth-averaged water quality model was developed to estimate the fate and transport of four contaminants in the San Joaquin River of California. The modeling results indicate that it took 20 days for these contaminants to transport from the upstream to the downstream in the research domain. These models can be effectively used for inland surface water restoration and management

The response of microalgal biomass and community composition to the chemical and physical dynamics of two Eastern Cape estuaries

Water quality characteristics of estuaries are influenced by both natural and anthropogenic activities. Estuaries situated in coastal urban areas are exposed to more perturbations than those in rural settings. This study determined the drivers of phytoplankton biomass and community composition in two Eastern Cape estuaries and evaluated the anthropogenic activities that influence the overall health of each estuary. The estuaries were sampled in summer and winter (2014, 2015). The water quality of the estuaries was determined by measuring the variability in physico-chemical parameters (salinity, temperature, dissolved oxygen and pH), nutrients, phytoplankton biomass and composition and faecal bacteria. Results show that both Mngazana and Nahoon are well oxygenated (~ 6.0 mg l-¹) and are saline systems (~ 35 ppt) due to low freshwater inputs into both estuaries. Mngazana Estuary exhibited low nutrient inputs along the length of the estuary including Creeks 1 and 2 with low chlorophyll a (4.0 ± 0.2 µg Chl-a r¹) being recorded during this study while Nahoon Estuary had an overall chlorophyll a of 3.5 ± 0.3 µg Chl-a r¹. The two estuaries were dominated by flagellates with phytoplankton blooms recorded seasonally. Possible eutrophic conditions were evident along the upper reaches of Nahoon indicated by nutrient accumulation and by the presence of cyanobacteria. This also this reflected the possible anthropogenic nutrient inputs originating from the Nahoon catchment despite the low freshwater inflow. The presence of faecal bacteria counts along both estuaries indicates the need for further investigation into the source of faecal contamination. The use of nutrient analyses and phytoplankton composition during this study enabled a clear description of the water characteristics of the investigated estuaries. Furthermore, the need for the adherence to freshwater flow requirements of estuaries to limit the dominance of marine waters was clearly illustrated. Urban runoff due to impervious surfaces increases nutrient inputs into estuaries while rural use of estuarine waters introduces contaminants into the system; coupled with low freshwater inputs and eutrophic conditions, the deterioration of estuarine water quality over time demonstrates the need for effective monitoring of these systems

Dynamic tracing of fecal bacteria processes from a river basin to an estuary using a 2D/3D model

In this study fecal bacteria processes have been investigated using the EFDC 2D/3D model, based on local refinements using an orthogonal curvilinear grid system and with the model being applied to Ribble river basin, through the estuary, and into the Fylde Coast. The input fluxes from numerous minor rivers and streams within the basin were solved using a grid-based distributed hydrological model (GDHM) and a river network 1D model (RNM1D), developed by the authors. The detailed measured hydrodynamic data, included tide levels and nearshore ADCP 3D velocity field data at four sites and with data being recorded over a 2-week period. During this period continuous monitoring using four types of tracers was also undertaken across the Ribble basin, which included sampling for E. coli (EC) and Intestinal Enterococci (IE) parameters. Monitoring devices, in the form of buoys, were also used and moved with currents, driven by upstream discharges, tides, waves and wind. The results showed: (i) the grid system gave a detailed topographical representation of the transition zones from the river system to the estuary and coast, with the hydrodynamic and related solute transport processes being well represented; and (ii) the model predicted results fit generally well with the water stage, 3D flow velocity profiles (with some errors in the bottom and surface layers), and E. coli concentrations. The tracer paths from the injection sites were simulated using a Lagrangian particle tracking method, which showed that the tracer from the north bank outfalls and the Ribble river could propagate to the highly popular bathing beaches at Blackpool, particularly under the action of South Westerly winds. More detailed solutions and refinements (e.g., wave driven by the wind and density flows caused by different salinities, temperatures, and suspended sediment concentrations) need to be considered in the next stage of this study

Environmental consequences of a power plant shut-down: A three-dimensional water quality model of Dublin Bay

A hydro-environmental model is used to investigate the effect of cessation of thermal discharges from a power plant on the bathing water quality of Dublin Bay. Before closing down, cooling water from the plant was mixed with sewage effluent prior to its discharge, creating a warmer, less-saline buoyant pollutant plume that adversely affects the water quality of Dublin Bay. The model, calibrated to data from the period prior to the power-plant shut-down (Scenario 1), assessed the water quality following its shut-down under two scenarios; (i) Scenario 2: continued abstraction of water to dilute sewage effluents before discharge, and (ii) Scenario 3: sewage effluents are discharged directly into the Estuary. Comparison between scenarios was based on distribution of Escherichia coli (E. coli), a main bathing quality indicator. Scenarios 1 and 2, showed almost similar E. coli distribution patterns while Scenario 3 displayed significantly higher E. coli concentrations due to the increased stratification caused by the lack of prior dilution

Lakewide and Nearshore Microbial Water Quality Modelling in Lake St. Clair

Lake St. Clair is a freshwater lake in the Lake Huron to Erie corridor in the Great Lakes Basin. Millions of people in Canada and the United States rely on that water source for drinking, fishing and recreational purposes. Lake St. Clair’s watershed is heavily impacted by human activity, which can result in contamination of its waters by fecal matter of human or animal origin containing waterborne pathogens, and thus pose a direct threat to human health. Common sources of such pollution include combined sewer overflows, wastewater treatment plant bypasses, and agricultural application of manure derived from animal fecal waste. Several such sources are present in Windsor Essex County (WEC), Ontario, Canada, which is located along the southern edge of Lake St. Clair. Two popular public beaches and drinking water intakes are located in the nearshore region adjacent to the southern edge. Fecal microbial pollution is currently monitoring using fecal indicator bacteria (FIB), such as Escherichia coli (E. coli). Monitoring methods have several limitations including their inability to predict water quality in real-time or in advance, or to identify potential sources of contamination for more effective management. Mathematical models are tools that can be very effective and complementary to monitoring in overcoming its limitations. Model predictions can be real-time or near real-time and also help to identify or exonerate potential sources of microbial pollution. In the current study, two types of modelling approaches that are commonly being used in the assessment of microbial contamination in beach waters and lakes were investigated: statistical modelling based on multiple linear regression (MLR) and hydrodynamic-ecological modelling. The statistical MLR models developed for Sandpoint Beach in Lake St. Clair showed higher accuracy in the range 64-78%, for predicting both exceedance and non-exceedance of the applicable standard, as compared to 54% accuracy obtained using the current method based on E. coli measurements. Amongst the MLR models developed, an increase of about 5-14% in model performance was observed when qualitative sky weather condition was included. Results with mechanistic structured grid high-resolution AEM3D model developed for Lake St. Clair showed that four major tributaries (Thames, Sydenham, St. Clair and Clinton River) are unlikely to be responsible for the E. coli exceedances of provincial guideline observed at Sandpoint Beach. Amongst the major tributaries, predicted E. coli concentrations were dominated by the contribution of St. Clair River for most of Lake St. Clair. The maximum predicted E. coli concentration from the combined input of the major tributaries was less than 100 CFU/100 ml for most of the lake and less than 10 CFU/100 ml at Sandpoint Beach. Predicted E. coli were significantly affected by varying water temperature and sunlight result in the temporal and diurnal dynamics of microbial water quality in Lake St. Clair. About 12–148% differences in predicted E. coli concentrations were observed at six drinking water intakes located in Lake St. Clair when time-variable decay rates were used instead of a constant decay rate. Also, on average nighttime E. coli predictions were 21–68% higher at these water intakes, as compared to daytime levels. Results from the AEM3D model showed that while the flow contribution of eight smaller tributaries in Windsor Essex Region to the lake is insignificant (less than 0.2%), their contribution to the adjacent nearshore region along the southern edge of Lake St. Clair could be quite significant. Within about 1 km from the shoreline of this nearshore region, flow contributions from the small tributaries were estimated in the range between 18-35%, while their contribution to E. coli concentration was estimated to be more than 80%. Results with mechanistic unstructured grid TUFLOW-FV/AED2+ lakewide model and with a finer mesh nested model over a 2 km region surrounding Belle River showed differences of up to a factor of four in predicted E. coli concentrations at adjacent Lakeview Park West Beach (LP Beach). The differences reduced to a factor of up to 1.3 at nearby Lakeshore WTP intake located about one km away from shore. While the average contribution of the Belle River to E. coli concentrations at Lakeshore WTP intake was predicted to be \u3c20%, the contribution increased to \u3e80% when higher concentrations (10-35 CFU/ 100 ml) were predicted. The results also indicate that the construction of the marina may have contributed to some increase in E. coli concentrations at LP Beach from the external sources considered. However, construction of a new 150 m jetty in 2018, in place of the 25 m jetty separating Belle River from LP Beach, is expected to reduce the E. coli concentrations at LP Beach from the same sources by about 80%

Modelling the Water Quality of the Patos Lagoon, Brazil

A two-dimensional depth integrated finite element modelling suite comprising the flow model TELEN4AC-2D and the water quality model WQFLOW-2D has been calibrated to simulate the physics and chemistry of the Patos Lagoon and Estuary system in southern Brazil for the investigation of nutrients, primary production and faecal bacteria. The model has been evaluated for use as a predictive tool to aid the decision making process for the rehabilitation and management of the shallow embayment of Saco da Mangueira adjacent to the city of Rio Grande in the lower Patos Estuary. This bay is one of several shallow areas bordering the city which suffers from the water quality pollution problems associated with eutrophication due to the influence of multiple and conflicting human impacts including the disposal of waste water from domestic and industrial sources such as the fertiliser industry, fish processing, and petroleum refining. The validated flow model indicated a very weak circulation in the Saco da Mangueira with velocities an order of magnitude lower than in the estuary. Simulations conducted to evaluate transport and mixing time scales demonstrated limited water exchange between the bay and the estuary principally controlled by wind direction and duration, with efolding flushing times between 21 and 45 days using observed wind and river flow data. The water quality modelling undertaken in this research represents the first reported application of WQFL0W-2D to the Patos lagoon and estuary system, and the first water quality modelling exercise of any kind reported to date for the Saco da Mangueira. Calibration and validation processes demonstrated that WQFLOW-2D could simulate annual average observed concentrations of water quality variables consistently and confirmed the eutrophic nature of the waters within the Saco da Mangueira. The model was used as a comparative tool to evaluate the predicted performance of hypothetical engineering schemes designed to improve the water quality within the bay and water exchange at the mouth. A number of recommendations were made including an imperative requirement for the collection of pollutant input and process data to reduce the level of uncertainty associated with the water quality model.HR Wallingford Limite