This study examines the major ion chemistry of the Tenga River in the Dahung area in Arunachal Pradesh of India. The samplings were carried out during the post-monsoon period and all the analysis were carried out following the standard procedures. Tenga river water is characterised by the following relative ionic abundances: Mg > Ca > Na > K > Fe and SO4 - > Cl- > NO3 > PO4 -. Hydrochemical analyses indicate that dolomite weathering and dissolution of feldspathoid group and evaporite sediments are the major contributing factors towards the composition of the river water. In the absence of major industrial activity in the region, the other significant impact on water quality of the river is due to the agricultural and livestock operations through farmland runoff.
