Assessment of water quality of Dhansiri River at Interstate Boundary of Assam and Nagaland (North-Eastern India) using Principal Component Analysis

Abstract

Effective management of transboundary river systems is a critical global challenge, particularly in developing regions where water quality degradation can fuel interstate conflict and hinder sustainable development. This study applies Principal Component Analysis (PCA), a robust multivariate statistical technique, to evaluate the water quality of the Dhansiri river, a tributary of the river Brahmaputra flowing along the interstate boundary between Assam and Nagaland in north-eastern India. Quarterly monitoring data from January 2022 to June 2024, comprising 19 physicochemical and biological parameters from five stations, were analyzed to identify key pollution sources and regional trends. PCA reduced data dimensionality while preserving explanatory power, revealing site-specific pollution patterns. Upstream stations (Nagaland) exhibited strong loadings for pH, hardness and calcium, indicating geological influence from limestone terrain. Downstream sites (Assam) showed elevated biochemical oxygen demand, nitrate and fecal coliforms, tracing pollution to untreated sewage, agricultural runoff and industrial discharge including effluents from cement plants. For instance, Bokajan and Numaligarh (Assam) stations reflected distinct anthropogenic pressures. These findings underscore PCA’s applicability in transboundary water governance, offering a data-driven framework for policymakers worldwide. The methodology and results are especially relevant for developing countries grappling with similar hydrological and institutional complexities, making the study a transferable model for integrated river basin management.