Multivariate Assessment of Seasonal Water Quality Dynamics in the Tuivawl River, Mizoram, Northeast India: Implications for Sustainable Water Resource Management

Abstract

Rivers of NE India are undercharacterised and lie within the Indo-Burma Biodiversity Hotspot. This study established the first multivariate baseline of surface water quality of the Tuivawl River, Saitual District, Mizoram, and determined whether water quality is under the primary control of season or longitudinal position along the river channel. Seventy-two site-month observations were collected from three stations over a ~25 km reach from November 2022 to December 2024, spanning winter, summer and rainy seasons. Fifteen physico-chemical and bacteriological parameters were measured following APHA standard methods and analysed using Kruskal-Wallis H tests, Pearson correlation, PCA, weighted arithmetic WQI and K-means clustering. Eleven of the 13 physico-chemical parameters differed significantly among seasons (p < 0.05), with none differing among sites, indicating that season exerts greater control on water quality than longitudinal position in this reach. PCA extracted three components explaining 68.01% of total variance: mineralisation-ionic enrichment (PC1: 42.01%), thermal transport (PC2: 14.50%) and nutrient-biological activity (PC3: 11.49%). Mean WQI was 94.59 ± 59.48 (“Very Poor”) in winter, rising to 222.75 ± 198.61 (“Unsuitable”) in summer and 385.83 ± 239.46 (“Wastewater”) in the rainy season, driven by coliform counts reaching the detection limit at all three stations. K-means clustering (k = 3) reproduced the seasonal structure without any site signal.  Health risk in this river is not adequately captured by physico-chemical monitoring alone, and the dataset provides a pre-degradation baseline to guide sanitation planning, riparian protection and sustainable water resource management in Mizoram.