Effects of Reservoirs on Streamflow in the Boreal Region

The circumpolar boreal region is generally well endowed with water resources relative to its low population. The most common natural river flow pattern is the nival regime in which snowfall accumulated during the long winter is rapidly melted in the spring, releasing large meltwater fluxes that cause the hydrograph to peak. Human development has altered this flow rhythm through water use and consumption. Reservoirs constructed for hydro-power production change the timing of flow while water withdrawal for consumptive purposes causes changes in both the timing and the amount of discharge. The most profound effects come with river diversion which alters the annual flows and re-distributes the monthly discharges, with the donor river losing water and the recipient river and the connecting channel gaining flows. Examples are drawn from Canada and Siberia to illustrate the effects of reservoir operation on streamflow. Flow regulation produces hydrological impacts that have local to regional consequences.