Is the entropy-weighted water quality index a suitable index for evaluating the groundwater quality in Ha'il, Saudi Arabia?

Abstract This study examined the groundwater quality in Ha'il according to World Health Organization (WHO) standards using the entropy-weighted water quality index (EWQI) more accurately. The study investigated several parameters in groundwater quality and found that more than 75% of the changes in Ha'il can be attributed to four main factors (MF1, MF2, MF3, and MF4). The MF1 was found to have the biggest role in controlling more than 33% of the changes in the water quality. Due to the entropy calculations for each parameter, zinc was found to have the highest rate of influence on groundwater quality. The results of the EWQI showed that the highest number of samples (76%) had Rank 2 and good quality. Also, it was tried to couple EWQI with machine-learning techniques to improve the model performance and survey the related results in this study. The results showed that the efficiency criteria are improved noticeably. Root-mean-square error decreases by 25%, and the determination coefficient (R2) increases by 27.94%.