HR: 17:15h
AN: GC44A-07 INVITED    [Abstracts]
TI: Changes in the Discharge of Major Rivers in the Ganges, the Brahmaputra and the Yangtze Rivers During the Next 100 years
AU: * Webster, P J
EM: pjw@eas.gatech.edu
AF: School of Earth & Atmospheric Sciences Georgia Institute of Technology, 311 Ferst Dr NW, Atlanta, GA 30332,
AU: Jian, J
EM: jun.jian@eas.gatech.edu
AF: School of Earth & Atmospheric Sciences Georgia Institute of Technology, 311 Ferst Dr NW, Atlanta, GA 30332,
AB: Our goal is to estimate the behavior of future river discharge in the Brahmaputra, Ganges, and Yangtze Rivers, forced by increasing greenhouse gas concentrations. Such determinations are critical in order to determine risk from flooding or droughts in the context of rapidly increasing populations. We concentrate on the hydrological discharge in three major river basins: the Yangtze, the Ganges, and the Brahmaputra as these rivers are critical for survival of a large proportion of humankind, where there are extensive historical records of discharge and proven relationships with sea surface temperature variations in the present era. We aim to project the river discharge during the next 100 years under the full range of IPCC greenhouse gas scenarios. We use the suite of IPCC-AR4 CMIP3 climate models to determine future discharge. However, the projected precipitation from models have very large regional model-to-model variability, which limits the ability to quantify the regional precipitation trends. To overcome this problem, we use a basic statistical quantile-to-quantile technique to build a mapping index linking each modeled 20th century river basin precipitation and associated observed 20th century discharge. Model adequacy is stratified by their ability to simulate the observed annual cycle and a set of models chosen for each river basin. Using the "good" models so chosen, the future discharge of the Yangtze, the Ganges, and the Brahmaputra over the next 100 years are for different emission scenarios. The Yangtze, Ganges, Brahmaputra mean wet season river discharges are projected to increase up to 15-25% at the end of 21st century under high greenhouse gases concentration scenarios (SRESA1B and SRESA2). Besides greater river discharge, flooding risk determined by year-to-year variability also increases substantially. Scenarios with fixed greenhouse gas concentration suggest little discharge change on mean value, year-to-year variation, and model-to-model deviation. It is estimated that the Yangtze, Brahmaputra and Ganges river basins might have population doubling times of between 45 and 90 years. Based on these numbers, the amount of fresh water available in these river basins for agriculture, human consumption and industrial use in the present era are compared with that will be available in the future. Despite the anticipated increase in river discharge, the amount of fresh water available per capita is expected to decrease by 50-75%, suggesting the approach of a societal-climate tipping point.
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 1620 Climate dynamics (0429, 3309)
DE: 1630 Impacts of global change (1225)
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting