Evaluation of E.coli losses in a tidal river network using a refined 1-D numerical model

Predicting the rate of Escherischia coli (E.coli) loss in a river network is one of the key conditions required in the management of bathing waters, with well verified numerical models being effective tools used to predict bathing water quality in regions with limited field data. In this study, a unique finite volume method (FVM) one-dimensional model is firstly developed to solve the mass transport process in river networks, with multiple moving stagnation points. The model is then applied to predict the concentration distribution of E.coli in the river Ribble network, UK, where the phenomena of multiple stagnation points and different flow directions appear extensively in a tidal sub-channel network. Validation of the model demonstrates that the proposed method gives reasonably accurate solution. The verification results show that the model predictions generally agree well with measured discharges, water levels and E.coli concentration values, with mass conservation of the solution reaching 99.0% within 12 days for the Ribble case. An analysis of 16 one-year scenario runs for the Ribble network shows that the main reduction in E.coli concentrations occurs in the riverine and estuarine regions due to the relatively large decay rate in the brackish riverine waters and the long retention time, due to the complex river discharge patterns and the tidal flows in the regions

Hydro-epidemiological modelling of bacterial transport and decay in nearshore coastal waters

In recent years, society has become more aware and concerned with the environmental and human health impacts of population growth and urbanisation. In response, a number of legislative measures have been introduced within Europe (and globally), which have sparked much cross-disciplinary research aimed at predicting and quantifying these impacts, and suggesting mitigation measures. In response to such measures this paper is focused on improving current understanding of, and simulating water quality, in the form of bacterial transport and decay, in the aquatic environment and particularly in macro-tidal environments. A number of 2D and 3D hydro-epidemiological models were developed using the TELEMAC suite to predict faecal bacterial levels for a data rich pilot site, namely Swansea Bay, located in the south west of the UK, where more than 7,000 FIO samples were taken and analysed over a two year period. A comparison of 2D and 3D modelling approaches highlights the importance of accurately representing source momentum terms in hydro-epidemiological models. Improvements in 2D model bacterial concentration predictions were achieved by the application of a novel method for representing beach sources within the nearshore zone of a macro-tidal environment. In addition, the use of a depth-varying decay rate was found to enhance the prediction of Faecal Indicator Organism concentrations in 3D models. Recommendations are made for the use of these novel approaches in future modelling studies

Proceedings of the XXVIIIth TELEMAC User Conference 18-19 October 2022

Hydrodynamic

Kentucky Water Resources Research Institute Annual Technical Report FY 2010

The 2010 Annual Technical Report for Kentucky consolidates reporting requirements for the Section 104(b) base grant award into a single document that includes: 1) a synopsis of each research project that was conducted during the period, 2) citations for related publications, reports, and presentations, 3) a description of information transfer activities, 4) a summary of student support during the reporting period, and 5) notable awards and achievements during the year

Integrated modelling of hydrological and hydrodynamic processes, dynamic bacteria decay with climate change and intensive farming in riverine and estuarine water

The water quality deteriorations in river and estuarine waters are a global issue. Particularly, the water quality impairment due to contamination of Faecal Bacteria Indicator, such as E. coli and Faecal Coliform in river channel, estuary bathing and shellfish waters are of special interests due to potential risks to human health. These indicators are important in water quality assessment outlined in both EU Water Framework Directive and US Clear Water Act. The hypothesis of the study is that the global climate change and intensive farming would cause severe deterioration to faecal coliform levels in these water bodies. Approaches to quantify these impacts are carried out with numerically modelling through catchment model Soil and Water Assessment Tool (SWAT) and hydrodynamic model DIVAST with the focus in the coastal catchment of river Frome and Piddle connected to a natural harbour in Dorset, southern England. Firstly, the SWAT model is employed to assess the catchment flow regime and set up the baseline condition of river flow in both hourly and daily time step. The hourly simulation using Green & Ampt infiltration has excellent model performance with Nash Sutcliff Efficiency (NSE) an

Integrated modelling studies of solute transport in river basin systems

Surface water and groundwater systems are linked dynamically in reality as the one generally impacts directly on the other. Traditionally, however, these two water bodies have more often than not been treated as different entities by water managers and other professionals. The issue of the compartmentality of these two resources is the main focus of the study described herein. In this study, an existing 1D-2D hydro-environmental surface water model that includes a groundwater model (DIVAST-SG) has been extended to 2-D and refined through testing against three laboratory studies. A surface water-groundwater system model using foam to replicate groundwater material was created in the laboratory and the results of the hydrodynamic processes (i.e. water elevations and flowpaths) were compared with the numerical model predictions. On the whole the comparisons showed good agreement. However, dye studies for replicating pollutant transport did not show such good agreement and this discrepancy was thought to be due to a number of reasons. In the second series of studies, the groundwater material was then replaced with the more traditional sand embankment and again results for both hydrodynamic and solute transport processes (by way of dye studies) from the laboratory set up were compared with the numerical predictions which were in almost perfect agreement. In the same tidal basin, a Severn Estuary model was then designed and set up. Although there were differences from the prototype owing to space and scaling difficulties, the results showed good agreement for both tidal amplitudes and tidal currents with the predictions from the numerical model and particularly the tidal amplitudes were found to compare favourably with field studies. Tracer results from the physical model also showed consistency with simulations from previous researchers in the main estuary. Overall, the purpose of this study, which was to investigate the manner in which flow and solute (conservative tracer) fluxes interacted between surface and sub-surface flows, for simulated riverine and tidal conditions, has been achieved. These experiments and the corresponding datasets are thought to be unique

Development of a hydroinformatics software tool: Enteric bacteria transport modelling associated with sediment transport.

This study presents investigations on microbiological water quality numerical modelling. Emphases have been laid on the model development by implementing state-of-the-art technologies in terms of the new research branch in water science, established in 1980s - hydroinformatics. In the study, new mathematical equations for modelling bacterial re-suspension from bottom sediments and disappearance due to sediment deposition are established. Therefore, the bacterial re-suspension from bottom sediments is firstly modelled. The bacterial sedimentation equations presenting bacterial disappearance due to sediments settling process in natural waters is also introduced, which is independent from the well- known first order decay model. Based on the new equations, an integrated 1-D and 2-D hydroinformatics water quality simulation model has been developed, carrying out sediment transport associated bacteriological water quality modelling. The model therefore performs modelling work including hydrodynamic modelling, sediment transport modelling and bacterial decay modelling which is associated with the sediment transport processes. The new bacterial decay model encompasses the terms of bacterial first order decay, bacterial resuspension and the bacterial deposition. Object-oriented methodologies are employed in the integration of the sediment-associated multi-dimensional water quality model to encompass well-tested existing modules, by implementing Fortran 90 and Visual Basic 6.0 programming languages to deploy the advanced numerical schemes and provide a state-of-the-art GUI system. Validation and calibration of the integrated sediment-linked water quality model has been carried out in its application to the Bristol Channel and Severn Estuary by using vast volumes of data from in-situ field measurements including: diffuse faecal indicator sources of 29 riverine inputs point faecal indicators sources of 34 WwTW outfalls daily- recording hourly observed sunlight radiation data downstream real-time tidal water elevation boundary data upstream Severn River flowrate variations and the bathymetry data across the 1-D and 2-D domain. Satisfied calibration results were obtained and the model was successfully validated to estimate the enterococci concentration levels at beach bathing water compliance locations, thereby could now be applied to other estuarine environments

The occurrence and origin of salinity in non-coastal groundwater in the Waikato region

Aims The aims of this project are to describe the occurrence, and determine the origin of non-coastal saline groundwater in the Waikato region. High salinity limits the use of the water for supply and agricultural use. Understanding the origin and distribution of non-coastal salinity will assist with development and management of groundwater resources in the Waikato. Method The occurrence of non-coastal groundwater salinity was investigated by examining driller’s records and regional council groundwater quality information. Selected wells were sampled for water quality analyses and temperatures were profiled where possible. Water quality analyses include halogens such as chloride, fluoride, iodide and bromide. Ratios of these ions are useful to differentiate between geothermal and seawater origins of salinity (Hem, 1992). Other ionic ratio approaches for differentiating sources and influences on salinity such as those developed by Alcala and Emilio (2008) and Sanchez-Martos et al., (2002), may also be applied. Potential sources of salinity include seawater, connate water, geothermal and anthropogenic influences. The hydrogeologic settings of saline occurrence were also investigated, to explore the potential to predict further occurrence. Results Numerous occurrences of non-coastal saline groundwater have been observed in the Waikato region. Where possible, wells with relatively high total dissolved solids (TDS) were selected for further investigation. Several groundwater samples are moderately saline and exceed the TDS drinking water aesthetic guideline of 1,000 g m-3 (Ministry of Health, 2008). Selected ion ratios (predominantly halogens) were used to assist in differentiating between influences on salinity such as seawater and geothermal. Bromide to iodide ratios, in particular, infer a greater geothermal influence on salinity, although other ratios are not definitive. The anomalously elevated salinity observed appears natural but nevertheless has constrained localised groundwater resource development for dairy factory, industrial and prison water supply use. Further work may show some relationship with geology or tectonics, which could assist prediction of inland saline groundwater occurrence