<p>Water is the main supporter of the sustainability of life and ecosystems on Earth. Water quality, quantity, and security have become a global challenge that requires interventions for their conservation and protection. Quality water preserves human health and the aquatic environment. Surface waters in the Mirushë River watershed represent a vital resource for the community and biodiversity that lives within this watershed. This study aims to address the water quality of the Mirushë River using the method provided by the United States National Sanitation Foundation. The Water quality index calculation was carried out for the Bajë and Volljak monitoring stations with data for the period 2019–2023 and included the parameters: water temperature, turbidity, pH, dissolved oxygen, biochemical oxygen demand, total dissolved solids, nitrates, and phosphates. The water quality index at the Bajë station showed values ​​from 78.57 to 92.86, while at the Volljak station 73.48 to 80.74, classifying the Mirushë River water from average to good. The main objective of this paper was to see the variation of Water Quality Index (WQI) at these two monitoring stations of the Mirushë River, while the results obtained by this paper are an indicator that suggests taking preventive measures to prevent the deterioration of water health in the Mirushë River with the aim of its safe use and preservation of the aquatic ecosystem. The results of this paper also help address the objectives for sustainable development, specifically in development goal (Sustainable Development Goal 6) water and sanitation.</p>