"This study assesses the relationship between snow cover and river runoff in five large northern watersheds: the Ob, Yenise, Lena, Yukon, and Mackenzie basins. Remotely sensed snow cover extent (1966-2002), snow water equivalent data (1988-2001), and river discharge at the river mouths (1966-1999) are used to assess the association between snow cover and river runoff cycles. Long-term air temperature (1966-2002) and precipitation data (1988-2002) are used to explain the differences in snow cover conditions among different watersheds and different years. Good consistency is found between basin snow cover extent area and snow water equivalent. A clear correspondence of streamflow to basin snow cover change is identified in all the basins. The extreme cases of temperature, precipitation, snow water equivalent, and the associated discharge conditions have also been investigated, and no variable has a predominant role in determining the magnitude or timing of snow pack and stream flow regime"