## 3 Research Methodology
### Datasets
#### 3.1.2 Data Collection  
The model is trained using dataset 1, which is sourced from China. The samples were collected from several large lakes and rivers. [PERSON] et al. (2014) also employed this dataset in their research. The water's quality is represented by the final column, which is designated as a consequence. A total of five columns are present, with four of them defining the water's parameters--potential of hydrogen (pH), dissolved oxygen (DO), concentration of chemical oxygen demand (CODMn), and ammonia (NH3-N)--in Table 3. The water quality was classified and predicted using six classes, ranging from excellent to bad: 1, 2, 3, 4, 5, and 6 (worse than 5). A total number of 34,607 data points are in this dataset ([PERSON] et al., 2014).  
The BWDB is the source of dataset 2, which is shown in Figure 2, and the data were collected from the southern region divisions of Khulina, Barisal, and Chittagong for the period of 2012-13. A total of 69 groundwater samples (duplicate) were analyzed in the laboratories of BUET, the University of Dhaka, and DPHE to verify and cross-check the quality of the analysis. Two categories of water quality parameters were collected, namely physical parameters and chemical parameters. The physical parameters include temperature, pH, Eh, EC, salinity, TDS, and arsenic. The chemical parameters that were collected include significant anions, cations, and trace elements. The values of the water quality parameters were determined in the field using field test kits, as well as in the laboratories of the BWDB, Dhaka University, BUET, and DPHE.  
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Parameters** & **Units** & **Banglades** **Standards’ **Drinking** **Limit ([PERSON] et al., 2014)** & **WHO Drinking** **Limit ([PERSON] et al., 2014)** \\ \hline pH & – & 6.5–8.5 & 6.5–8.5 \\ \hline DO & mg/L & 5 & 6 \\ \hline COD & mg/L & 10 & 4 \\ \hline NH3-N & mg/L & 0.5 & 0.5 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Water quality standards.  
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**pH** & **DO (mg/L)** & **CODMn (mg/L)** & **NH3-N (mg/L)** & **Result** \\ \hline
7.09 & 10 & 5.7 & 0.33 & 3 \\ \hline
6.8 & 11.6 & 6.3 & 0.59 & 4 \\ \hline
9.41 & 7.94 & 10.8 & 0.1 & 6 \\ \hline
7.65 & 7.21 & 4 & 0.44 & 2 \\ \hline
8.57 & 10.9 & 0 & 0.15 & 1 \\ \hline
7.85 & 7.57 & 9.2 & 1.82 & 5 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Features of dataset 1.  
In this dataset, there are a total of 1045 data points and 28 parameters, but WQI is not mentioned in this dataset.  
Table 4 shows the monitoring events and the total number of samples taken in the dry and wet seasons for well nests, line wells (up to 100 m), line wells (up to 30 m), and surface water. Line wells are a series of water wells that are drilled at regular intervals along a straight line to access or monitor a broader area. In contrast, nested wells are multiple wells that are drilled at a single location but at varying depths to target specific aquifer strata. The primary distinction is that line wells extend horizontally throughout a region, whereas nested wells are vertically aligned at a single location.  
Figure 2: Location of collected samples in dataset 2 (Image source is the BWDB [34]).