## 4 Groundwater Level Prediction Techniques
### Physically Based Numerical Method--Modflow  
Physically based numerical models remain the best methods to study the characteristics of groundwater. This is because they require comprehensive details of the physical properties of aquifer. Among the different physically based numerical models, MOD-FLOW is the most used model in the literature; it models groundwater movement in three dimensions using finite differences. Until the last decade, MODFLOW was used extensively, especially when sufficient data are not available. Depending upon the problem, several approaches are designed for MODFLOW, i.e., the head-oriented approach (HOA) is used to determine the three-dimensional flow of groundwater, the velocity-oriented approach (VOA) comes in handy when computing the velocity of flowing groundwater [48]. However, certain steps are needed to formulate such a model, i.e., grid design, boundary setting, time steps, and hydrologic and aquifer characteristic variables selection. [PERSON] and [PERSON] [49] calibrated MODFLOW in Uttar Pradesh, India to simulate groundwater levels. Data mostly comprising of water levels collected between 2005 and 2013 were used in the study. In addition, the impact of pumping and recharge rate on the groundwater levels was also studied, and it aimed to predict the groundwater levels for five years ahead. The results showed a declining trend in groundwater levels in the region. \begin{table}
\begin{tabular}{l l l l l} \hline \hline
**Data Shape** & **Data Classification** & **Data Source** & **Access Date** & **Availability** \\ \hline \multirow{2}{*}{Shapefile or Vectorial} & \multirow{2}{*}{Rock permeability and porosity} & [[https://borealsdata.ca/dataset.shtml?](https://borealsdata.ca/dataset.shtml?)]([https://borealsdata.ca/dataset.shtml?](https://borealsdata.ca/dataset.shtml?)) & \multirow{2}{*}{(10 February 2023)} & \multirow{2}{*}{Worldwide} \\  & & persistield=\(\text{dei}\)?3A10.5683/SP2/TTJNIU & & \\ \hline \multirow{2}{*}{Raster} & \multirow{2}{*}{Climatic data} & [[https://apps.ecmwf.int/datasets/](https://apps.ecmwf.int/datasets/)]([https://apps.ecmwf.int/datasets/](https://apps.ecmwf.int/datasets/)) & (10 February 2023) & \multirow{2}{*}{Worldwide} \\ \hline \multirow{2}{*}{Raster} & MODIS products & [[https://appeears.earthdatcloud.nasa.gov/](https://appeears.earthdatcloud.nasa.gov/)]([https://appeears.earthdatcloud.nasa.gov/](https://appeears.earthdatcloud.nasa.gov/)) & (10 February 2023) & \multirow{2}{*}{Worldwide} \\ \hline \multirow{2}{*}{Raster} & Digital surface model (DSM) & [[https://asterweb.jpl.nasa.gov/gglem.asp](https://asterweb.jpl.nasa.gov/gglem.asp)]([https://asterweb.jpl.nasa.gov/gglem.asp](https://asterweb.jpl.nasa.gov/gglem.asp)) & (10 February 2023) & \multirow{2}{*}{Worldwide} \\ \hline Database & Climatic data & [[https://swat.tamu.edu/data/cfsr](https://swat.tamu.edu/data/cfsr)]([https://swat.tamu.edu/data/cfsr](https://swat.tamu.edu/data/cfsr)) & (10 February 2023) & \multirow{2}{*}{Worldwide} \\ \hline Database & Climate projections & [[https://esgf-data.dkrz.de/search/esgf-dkrz/](https://esgf-data.dkrz.de/search/esgf-dkrz/)]([https://esgf-data.dkrz.de/search/esgf-dkrz/](https://esgf-data.dkrz.de/search/esgf-dkrz/)) & (10 February 2023) & \multirow{2}{*}{Worldwide} \\ \hline Database & River network spatial data & [[https://water.ieng.ox./web/giskrf?](https://water.ieng.ox./web/giskrf?)]([https://water.ieng.ox./web/giskrf?](https://water.ieng.ox./web/giskrf?)) & \multirow{2}{*}{(10 February 2023)} & \multirow{2}{*}{Korea} \\  & & pNEN/LNO-89 & & \\ \hline \multirow{2}{*}{Database} & National Water Resources & \multirow{2}{*}{[[http://www.wamis.go.kr/](http://www.wamis.go.kr/)]([http://www.wamis.go.kr/](http://www.wamis.go.kr/))} & \multirow{2}{*}{(10 February 2023)} & \multirow{2}{*}{Worldwide} \\  & Management Comprehensive Information System & & & \\ \hline Database & Geographic information & Water Environment Geographic Information & (10 February 2023) & \multirow{2}{*}{Worldwide} \\ \hline \hline \end{tabular}
\end{table}