HIGHLIGHTS. DEM source influence the slope, resolution to basin perimeter of a watershed.The flat terrain area influences watershed delineation.The sub-basin co

Predicting and characterising groundwater flow and solute transport in engineering and hydrogeological applications, such as dimensioning tracer experiments, rely primarily on numerical modelling techniques. During software selection for numerical modelling, the accuracy of the results, financial costs of the simulation software, and computational resources should be considered. This study evaluates numerical modelling approaches and outlines the advantages and disadvantages of several simulators in terms of predictability, temporal control, and computational efficiency conducted in a single user and single computational resource set-up. A set of well-established flow and transport modelling simulators, such as MODFLOW/MT3DMS, FEFLOW, COMSOL Multiphysics, and DuMu^X were tested and compared. These numerical simulators are based on three numerical discretisation schemes, i.e., finite difference (FD), finite element (FE), and finite volume (FV). The influence of dispersivity, potentially an artefact of numerical modelling (numerical dispersion), was investigated in parametric studies, and results are compared with analytical solutions. At the same time, relative errors were assessed for a complex field scale example. This comparative study reveals that the FE-based simulators COMSOL and FEFLOW show higher accuracy for a specific range of dispersivities under forced gradient conditions than DuMu^X and MODFLOW/MT3DMS. FEFLOW performs better than COMSOL in regard to computational time both in single-core and multi-core computing. Overall computational time is lowest for the FD-based simulator MODFLOW/MT3DMS while the number of mesh elements is low (here < 12,800 elements). However, for finer discretisation, FE software FEFLOW performs faster.

Residents of Chattogram city areas in Bangladesh use drinking water from three sources, namely CWASA (Chattogram Water supply and Sewerage Authority), groundwater (tube-well), and commercial jar. In this study, we examined the quality of drinking water from these sources following an analytical and residents' perception. Water samples (both untreated and treated) from above three sources were collected from six locations across Chattogram city, and pH, total dissolved solids (TDS), total suspended solids (TSS), bicarbonate, electrical conductivity (EC), salinity, and microbial load were studied following the state-of-art testing methods. A total of 149 respondents were interviewed to understand their perception on the physical properties of water. The pH value of water from all sources and locations and irrespective of treatments, varied from 6.54 to 7.02. TDS of tube-well water in two locations exceeded the standard limit (1000 mg/l). In most locations, TSS varied from 40 to 1888 mg/l (treated and untreated) against the standard value of 10 mg/l, while bicarbonate of CWASA and tube-well water in most locations was also higher than the permissible amount (500 mg/l). Except for jar water, EC of CWASA and tube-well water (treated and untreated) in most locations were higher than the standard value (500 μS) and a similar situation was observed for salinity content. The microbial load was found beyond the permissible limit (0 CFU/ml) for all sources and locations. These parameters of water quality have also been reflected in residents' perceptions of drinking water. Respondents reported an unpleasant odour (56%), the presence of suspended particles (17%), and so CWASA water is not good for drinking (76%). Authorities (CWASA) need to take action toward a safe drinking water supply for residents.