Investigating Physicochemical Properties of Rangazak and Challou River in Ukhrul District, Manipur

Abstract

Rivers are the primary source of surface water and are important for the conservation of ecological integrity, biodiversity, fisheries, agriculture and domestic needs. Ecologically important but one of the least studied freshwater systems are the hill streams of North-East India. The present study is the first comprehensive assessment of the physico-chemical properties of the Rangazak and Challou Rivers of Ukhrul district, Manipur which are two important tributaries of the Chindwin-Irrawaddy drainage system. Water quality was monitored for a period of one year (October 2024 to August 2025) at six sampling sites (three sites per river) for water temperature, pH, total dissolved solids (TDS), dissolved oxygen (DO) and total alkalinity using standard methods. Data were statistically analyzed using one way ANOVA (p < 0.05). The annual mean water temperature was found to be 18.6 ± 0.8°C in the Challou River and 19.2 ± 0.5°C in the Rangazak River with a clear seasonal pattern from the winter (January) with 4.3–4.6°C to the maximum of 30.4°C in August. The pH was weakly alkaline to neutral (annual mean 8.1 ± 0.4 and 8.3 ± 0.2, respectively). DO levels remained high throughout (6.15–9.2 mg/L) with a clear inverse relationship with temperature and TDS values (annual mean: 150.9 ± 14.1 and 148.1 ± 9.2 mg/L) far below the WHO permissible limit of 500 mg/L. Total alkalinity was low to moderate (29.2 ± 3.4 and 27.4 ± 3.2 mg/L as CaCO3) and contributed primarily by OH− and CO32− ions with lowest values in April and highest in June. The seasonal variations in all parameters were typical of natural climatic and hydrological processes and not of human disturbance, suggesting that both rivers are relatively natural, healthy freshwater ecosystems. The results provide important baseline information for the conservation of fresh water biodiversity, habitat suitability assessment and sustainable river basin management in the region. Long-term monitoring and its integration with biological diversity studies is recommended.