Impact of Climate Change on River Discharge Projected by Multimodel Ensemble

Abstract

This study investigates the projections of river discharge for 24 major rivers in the world during the twenty-first century simulated by 19 coupled atmosphere–ocean general circulation models based on the Special Report on Emissions Scenarios A1B scenario. To reduce model bias and uncertainty, a weighted ensemble mean (WEM) is used for multimodel projections. Although it is difficult to reproduce the present river discharge in any single model, the WEM results produce more accurate reproduction for most rivers, except those affected by anthropogenic water usage. At the end of the twenty-first century, the annual mean precipitation, evaporation, and runoff increase in high latitudes of the Northern Hemisphere, southern to eastern Asia, and central Africa. In contrast, they decrease in the Mediterranean region, southern Africa, southern North America, and Central America. Although the geographical distribution of the changes in precipitation and runoff tends to coincide with that in the river discharge, it should be emphasized that the change in runoff at the upstream region affects the river flow in the downstream region. In high-latitude rivers (Amur, Lena, MacKenzie, Ob, Yenisei, and Yukon), the discharge increases, and the peak timing shifts earlier because of an earlier snowmelt caused by global warming. Discharge tends to decrease for the rivers in Europe to the Mediterranean region (Danube, Euphrates, and Rhine), and southern United Sates (Rio Grande).

Uncertainty in climate change impacts on water resources in the Rio Grande Basin, Brazil

“…An ensemble mean of the different outputs may be considered as a form to summarize the projections (Nohara et al, 2006;Christensen and Lettenmaier, 2007), however in our case it would probably mask the results since nearly half of the GCMs suggest an increase while the other half suggest a decrease in streamflow.…”

Comparison of climate change signals in CMIP3 and CMIP5 multi-model ensembles and implications for Central Asian glaciers

“…Huss, 2011;Farinotti et al, 2012), for river basins worldwide (e.g. Nohara et al, 2006), or for selected glaciers (e.g. Giesen and Oerlemans, 2010), no detailed assessments are available for Central Asia.…”

Potential Predictability of Seasonal Mean River Discharge in Dynamical Ensemble Prediction using MRI/JMA GCM

“…A linear river routing model with a constant effective current velocity of 0.4 m/s (GRiveT) is used (Nohara et al 2006). The model uses surface and subsurface runoffs computed in MJ98 as inputs and a global river channel network within a 0.5°× 0.5°grid box (TRIP; Oki and Sud 1998) as a constant boundary condition.…”

“…The data analyzed in the present study covers the 50-yr period from 1951 to 2000. The models captured the climatology of the P E, snow, and river discharges (Nakaegawa et al 2003;Nohara et al 2006), which provides an opportunity for further analysis.…”