The potential impacts of climate and forest changes on streamflow for micro-, meso- and macro-scale catchments in Norway

This is the authors' abstract. We don't add key points for this paper.

Six forest dominant catchments in Norway: two are micro- (< 10 km 2 ), two are meso- (< 1000 km 2 ) and two are macro-scale (> 10000 km 2 ) catchments. This study focuses on the combined climate and forest impacts on streamflow, hydrological components as well as flood and low flow levels. In addition, the relative contributions of climate and forest impacts are distinguished. This study provides the first hydrological projections in Norwegian catchments driven by both the climate projections and their corresponding forest projections. Due to warmer climate and higher precipitation under the Representative Concentration Pathway scenarios (RCP2.6 and RCP4.5), continuous increase in forest timber volume is projected in five out of six catchments. The combined effects of climate and forest development lead to median changes in annual streamflow ranging from −2 % to 8 %. Climate is the major driver of streamflow changes, and forest growth slightly offsets the increase in streamflow caused by climate and reduces runoff generation locally. Forest growth reduces the flood levels caused by climate by up to 3 % in all catchments except one with large clear-cutting areas. Forest growth leads to increase in low flow levels in three coniferous forest dominant catchments while it aggravates the low flow conditions in the catchments with high coverage of deciduous forest in the summer half-year. • We simulated forest growth and management using an advanced forest simulator. • We improved climate impact projections in six forest dominant catchments in Norway. • Climate change is the major driver of hydrological change in the future. • Forest growth reduces extremes in coniferous forest dominant catchments. • Forest growth aggravates low flow risk in deciduous forest dominant catchments.