Water quality models are broadly classified into two types one is physical and another is mathematical models [
41]. In addition, these models can be classified into 1D, 2D, and 3D based on the level of the complexity of the computer replica, the data requirements (including comprehensive records and limited data specification predictions), the type of approach used (such as physically based, conceptual, and empirical), the type of pollutant being modelled (such as nutrients, sediment, and salts), the regions of application, the nature of the model (whether it is deterministic or stochastic), the state being analyzed (whether it is a steady state or flexible simulation), and the spatial analysis method used (whether it is lumped or distributed) [
42].
Table 1 summarizes the benefits, drawbacks, suitability, and underlying assumptions of 1D, 2D, and 3D models. Alternatively, models can be classified as tactical, operational, strategic, or directed models, depending on their extent and spatial scales [
43]. The SKM (2011) classification scheme categorizes the water's quality models into catchment, in-stream, and ecological response models. Utilizing the rainfall-runoff mechanism as a basis, catchment models simulate the corresponding loads of pollutants. Simulated in-stream models represent in-stream aquatic quality processes and the hydrodynamic behaviour of flows. Ecological response models represent how an ecosystem reacts to stresses, such as changes in flow and water quality. Three categories exist for models of water quality: dynamic/stochastic, constant state, and dynamic models. Steady-state models are employed to analyze prolonged patterns and perform regular surveillance. Dynamic/stochastic models are designed for capturing short-term fluctuations, ongoing monitoring, and long-term patterns. Dynamic models are designed primarily for short-term mobility and continuous tracking to facilitate operational management [
44]. Water modelling models can be categorized as simulation or optimization models [
45]. The simulation model delineates and portrays alterations in water quality through a mathematical framework. Optimization models are frequently used to determine the minimum amount of alternative data required before conducting the model simulation. Models are commonly categorized based on their complexity, the water they are used for, and the water quality metrics they can predict. Applying a complicated model to a specific scenario becomes exceedingly challenging and costly due to the data needed [
46]. The primary controlling principle for model development is the law of preservation of energy, momentum, and mass preservation [
47]. Various formulas can be utilized to construct a water quality model, with a specific choice depending on the parameters to be modelled [
48]. A variety of water quality models, such as Agricultural Non-Point Source, AGWA, ANSWERS-2000, APEX, AQUA-TOX, BASINS, EFDC, EPD-RIV1, GLEAMS/CREAMS, HSPF, KINEROS2, LSPC, MIKE SHE, NLEAP, PRMS, QUAL2E, QUAL2K, SWAT, SWMM, WAM, WARMF, WASP7, WCS, and AquaChem, have been employed for the analysis of water quality.
Table 2.
An overview of Groundwater Numerical Models.
|
Scope |
Advantages |
Challenges |
Assumptions |
1D models |
Analysis of aquifer characteristics like hydraulic conductivity and porosity
Simulation of vertical contaminant transport phenomena
Insight into groundwater flow behavior in vertical columns
Decision support for well placement and groundwater remediation strategies
|
Applied rapidly to analyze lake and reservoir water with no prior calibration and with a limited database of measurements
The most straightforward and often employed techniques for analyzing the quality of river water
|
They cannot estimate the temporal fluctuation of concentration.
They do not encompass the intricate chemical, physical, and biological processes occurring in water.
|
Usually applicable to rivers, as well as estuaries as well as lakes with significant length-width ratios.
Applicable in extensive watercourses, rivers, brooks, and constricted passages
|
2D models |
Incorporation of horizontal variations in hydraulic properties and boundary conditions
Realistic representation of subsurface heterogeneity and flow pathways
Assessment of groundwater-surface water interactions
Analysis of the influences of land-use changes on groundwater resources
|
Specific characteristics can be analyzed at various time intervals, such as hourly, daily, weekly, monthly, and yearly.
It is important to assess water quality at different depths.
|
This process necessitates meticulous calibration and is very responsive to variations in numerous factors of water quality.
The models necessitate a greater amount of data and more proficient analytical users compared to one-dimensional models.
|
Applicable for simulating water quality primarily in reservoirs, deep rivers, and lakes.
Assumes substantial variations in water quality throughout both the lateral and longitudinal profiles of the watercourse.
|
3D models |
Comprehensive representation of subsurface hydrogeological systems
Capture of intricate flow patterns and heterogeneity
Site-specific assessments for detailed groundwater resource management
Addressing contemporary water resource challenges with improved accuracy and reliability
|
|
|
Relevant for investigating alterations in the water quality of dams, lakes, deep rivers, water bodies, estuaries, and seabays
|