Contemporary and Scenario Changes in River Runoff in the Don Basin

Abstract

The results presented in the study characterize variations of river runoff in the Don Basin in the period of instrumental observations and under scenario conditions of global anthropogenic warming, which are likely in the early current century. Integral-difference curves are used to identify long-term phases of higher/lower annual and seasonal runoff of the Don and its major tributaries over the period 1870–2010. The length of the phases varies from 10 years to many decades (for Don runoff of the dry seasons). The identified contrast phases show statistically significant difference in the seasonal runoff and, in the majority of rivers, annual runoff as well; it varies from 10 to >100%. A model of monthly water balance and ensemble-averaged model scenarios of changes in air temperature, precipitation, and evaporation under anthropogenic climate warming, developed under IPCC CMIP3 and CMIP5, are used to assess the possible changes in Don runoff at Razdorskaya in the first three decades of the current century. Scenario changes in the mean long-term river runoff are far less than its differences typical of the long-term phases of its higher/lower values and its changes caused by anthropogenic impact on drainage basins and in river channels.