In Peru, many environmental liabilities produce Acid Mine Drainage (AMD) which flow into rivers affecting their water quality, likewise, many of these liabilities transport large amounts of heavy metals, endangering every water-dependent living organism. In this context, for the evaluation of the parameters involved, we used the grey clustering method, which, based on the theory of grey systems, is presented as a remarkable alternative to the classical statistical methods. In this study we assessed the impact of the Ticapampa environmental liability on the water quality of Santa river using data collected in 2010 from four strategically located monitoring points along the river. The analyzed parameters were evaluated according to the parameters established by DS N° 004-2017-MINAM. Results showed that water quality from monitoring points located upstream (P1) and downstream (P2) with respect to the location of the environmental liability and according to Peruvian law, were of A1 (good) quality; which means that it can be purified using disinfectants. On the other hand, at two points located within the limit of the liability, the water quality was identified as A2 (moderate) and A3 (low) quality, which means it can be purified using conventional and special treatment respectively. Therefore, the grey clustering method has proven to be of great utility for water-quality-assessment related studies and can be applied in other studies which focus on this kind of analysis. In addition, the present results can be useful for Peruvian authorities in their decision making benefiting the communities nearby, animals and environment of study.