The Ob and the Lena Rivers are considered in the research. They are two biggest rivers of Russian Arctic and have the annual runoff 405 and 530 km ³ /year correspondingly. Analyse of multiyear data of Russian Hydrometeorological Survey (Roshydromet) and own measurements in the mouths areas allow to describe a tendency of water resource and water quality development in these regions according to climate change and human impact. Long-term river runoff and concentration of major and trace elements in water have been compare for regime data of Roshydromet and own field observation results. Increasing of some hydrological and hydrochemical parameters are available with declining of others simultaneously. Slight runoff increase lead to cleaning of water that have been marked for several pollutants for the Ob and Lena Rivers. In spite of “very dirty” water quality at Salekhard – Ob, amount of hazard pollution events (wastewater drainage) has been declined last decade with increase of water overloading by trace elements. Ecosystem well-being has within-year variability and slightly develops to higher ecosystem quality by the effect of climate change. Investigation of two rivers allow to say about the Big Arctic Rivers’ runoff tendency and ecological state enhancement in the Arctic Ocean inner shelf in general.