Surface water is an important source for drinking water supply in Brahmani River, Odisha, India. However, this basin plays an important role in local economy and ecosystem. This resource is extensively utilized for drinking, irrigation, and industrial activities globally. Thus, rapid use of water quality leads to serious water pollution. An attempt has been made in this work to understand the suitability for human consumption, considering 15 water quality (WQ) parameters collected yearly from seven water sources from Brahmani River Basin, Odisha. Time frame taken into consideration is 10 years (2013–2023). Integrated Determination of Objective Criteria Weights (IDOCRIW/I)-based water quality index (WQI) and MCDMs like Complex Proportional Assessment (COPRAS) method were applied to compute the results. The concept COPRAS was introduced in the current work, to apply weights and rough set theory to generate an impartial and trustworthy depiction of each sample location's overall pollution levels. The interpolation method such as Inverted Distance Weighted (IDW) was applied in ArcGIS software to produce the spatial map. The results showed that the river water is somewhat alkaline and the DO seems to be in good health when compared to the ranges or values provided by standard organizations as addressed by WHO, for evaluating WQ. Most of the parameters evaluated were found to fall within the allowable limits of the WHO standards. The results of integrated (I) weights indicated that WQ status belonged to good-poor quality of water. It is noted that principal stations such as J-(1), (2), (3) and (7) found to be high values, indicating poor H2O and having more impact on WQ. It was also come into fact that the location J-(7) had the second-highest integrated weight. This culminates primarily with point-based pollution such as wastewater from household and industrial sources, non-point sources such as agricultural activities and natural phenomena such as soil erosion and flooding. The visualization of the COPRAS method suggests that J-(1) was the most polluted station, based on its rank and its performance score (Ui = 100). The study recommended continuous pollution monitoring and local regulations to reduce the entrance of both diffuse and point-source pollution into the river. Hence, special attention should be given to maintain ecological sustainability. Moreover, the water quality methods, which are discussed extensively in the paper, can also provide an overall idea about indexing for further research.