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Evaluation of Climate Change Effects on Discharge Generation in a Heterogeneous Watershed

Author(s): Freddy Soria; So Kazama

Linked Author(s): So Kazama

Keywords: Glacierized catchments; Environmental flows

Abstract: Much has been said about the effects of climate change in watershed runoff generation, and the heterogeneous characteristics of mountainous systems deserves special attention. This paper analyzes the observations of current trends of temperature, precipitation, and discharge, and their probable future variations. The catchment is interesting as it is influenced by glacierized regions on the upstream region, and non-glacierized landscapes in the middle and lower part. Variations in glacier areal projections are estimated through temporal series of Landsat platforms (ETM 7 imagery), as the indicator of climate change effects. Future trends of climatic conditions are evaluated through comparing mean monthly projections from the Community Climate System Model version 3 CCSM3 and the Model for Interdisciplinary Research on Climate version 3.2 MIROC3.2hi-res (high resolution) Global Circulation Models GCM. Rise of discharge was significant for the periods 1982-1983 and 1997-1998 hit by ENSO events, where is observed and increase from 35%to 85%in terms of annual discharge at stations Zongo and Zongo plant. The trends suggest contribution from glaciers, as precipitation in stations nearby did not increase. Such effect seemed observable downstream at Santa Rita station, 70 km downstream, although difficult to confirm due to limited data, and a gap with no records few months after the phenomena, which cannot be confirmed because such rise seem to be a tendency that cannot be confirmed due to a gap with no records. Much more significant than the rise on annual discharge are the rising trends of temperatures, considering the relatively short period where they were observed (about thirty years). Deserves special attention the rise of teo degrees centigrade observed in La Paz station due to urban effect (Temperature=0.04years+11.06). The city is approximately 200km from the region of the glaciers, and although the direct effect is not accounted in this manuscript, some influence should definitely be expected. In stations located both on the dry Altiplano and on the eastern side of the Cordillera Real, showed “only” a rise of one degree centigrade, also within the same period of time (e.g. for El Alto: T=0.014t+7.47). Output data from the circulation models considered also showed an average rising trend of one degree centigrade (for CCSM3: T=0.023t+9.52, and for the MIROC3.2hi-res: T=0.028t+8.62). The effect of temperature should be direct, as the variable is an indicator of the rates of radiation in the region. For the near future, temperature rise is evident, but no such evidence is describes by the runs of the A1B scenario of the GCMs considered. The effect on snow generation should be immediate. Finally, based on the circulation models and the past observations, we can say that the glaciers would have a life of no more than 20 years (T=0.003t+10.06 as outlined by the CCSM3)


Year: 2010

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