Models

Since 2021, we have been developing a suite of models to highlight the flow and dispersal of Norovirus, faecal coliforms, and AMR genes, and other viruses from wastewater treatment plants into the environment, using CASCADE, TELEMAC, and DELFT3D as our primary modelling platforms. 

Following an intensive year-long water quality survey of the Conwy River, along with Combined Sewer Overflow (CSO) data provided by Dŵr Cymru/Welsh Water, our modelling objective is to simulate this period and better understand the controls and seasonal variability in viral dispersal through the river-estuary-coastal continuum.

We use the model to investigate extreme events or idealised scenarios and generate spatial risk maps to inform water quality managers. 

We have developed a high-resolution estuarine and catchment water quality model to simulate viral dispersal in the Conwy Estuary and the surrounding waters of Northwest Wales. This model has revealed that small or steep catchment-estuary systems like Conwy are sensitive to short-duration heavy rainfall events, whereas larger systems are more responsive to sustained weather fronts. These findings highlight the need for diverse modelling techniques and data resolutions when up-scaling nationally. 

The TELEMAC-2D model simulates theoretical viral peaks released from Llanrwst and Betws-y-Coed during a high-flow river event (October 20, 2013), using high-resolution spatial (~20m) and temporal (~15-minute) data. It has proven effective in shallow and intertidal regions, with tidal forces derived from the TPXO global tidal database. Bathymetry data is gathered from a variety of sources, including Admiralty charts, multibeam surveys, and LIDAR surveys.

Here we can observe the theoretical release and dispersal of a virus from a wastewater discharge point upstream in the Conwy River and its movement out into Conwy Bay. Initially, the model uses realistic hydrodynamics but theoretical data (e.g. position, timing and concentration), which will later be updated with actual field data as research progresses.

This model tracks how virus particles travel from Wastewater Treatment Works (WwTWs) in Betws-y-Coed and Llanrwst to the tidal limit. Itassumes a 30-minute pulse of virus particles entering a ‘virus free’ river. Virus concentrations are estimated based on measurements from each WwTW discharge point, with concentrations recorded in GC L-1. The discharge flows are set at 0.01 and 0.025 m3 s-1 and virus concentrations at 200,000 GC L-1.

River flows are based on historic data, with discharge at Llanrwst of ~6 m3 s-1, slightly below average flow. Currently, the model focuses on advection (movement with the flow) but will later include dispersion and in-stream processing as more field and laboratory data become available.

In addition, we have developed a salinity model for the North Wales coast using DELFT3D, which helps predict how salinity influences viral and bacterial dispersal and persistence in the coastal zone.