Ecological and hydrological responses to climate change in an urban-forested catchment, Nagara River basin, Japan

Annual changes in temperature, precipitation, and stream flow in a forested watershed were investigated by statistical analysis of various time-series records. Climate change was apparent not only in increased temperature but also in altered precipitation patterns including a longer no-precipitation period, shorter precipitation duration, and changes in the cyclical interval of heavy rain. Such climate changes led to a shorter precipitation-runoff response, a decreased amount of effective precipitation, and an increase in sediment yields due to increased evapotranspiration and decreased soil moisture. Rapid urbanisation in some forested watersheds may cause larger peak flows and decreased low flows by significantly reducing soil infiltration capacities. In contrast, forests have minimal influence on landslides, debris flows, or floods caused by extreme natural events. The combined effects of vegetation cover and topography explained the differences in summer runoff and maximum daily specific discharges among experimental catchments and in the behaviour of the same catchments during individual storms. The results of this study demonstrate that forests in headwater watersheds in Japan generally help create favourable water flow conditions and reduce water-related disasters. (C) 2012 Elsevier B.V. All rights reserved.