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CLIMATE CHANGE EFFECTS ON WATER RESOURCES AVAILABILITY OVER A SNOW INFLUENCED BASIN IN CENTRAL CHILE.

Congress: 2008
Author(s): additional author: XIMENA VARGAS
Civil engineer, Professor of Departamento de Ingeniería Civil de la Facultad de Ciencias Físicas y Matemáticas Universidad de Chile, xvargas@ing.uchile.cl

Keyword(s): Climate change, snow- influenced basin, water availability
AbstractIntroduction The results of global circulation model over certain zone show variations in two important weather variables necessary to assess water availability, temperature and rainfall. How to assess water availability at local scale in a reliable way is a nowaday’s challenge. To estimate water resources availability in the future taking in account the climate change, it is usual to use a hydrological simulation model that, previously, must be calibrated using observed variables. This study aim to assess water availability at local level, considering different possibilities inside the selected statistical downscaling method using as case study a snow influenced basin in central Chile. Objective To compare water availability obtained using a hydrological simulation model considering average and individual meteorological input series of A2 and B2 downscaled scenarios from 1980 to 2005. Methodology The water availability assessment was achieved through a downscaling of the weather impacted variables of a general climate model (GCM) and the application of these downscaled variables into an hydrological model to simulate the basin discharge. The data downscaling was done through SDSM 3.1 (Wilby and Dawson, 2004) a program with a statistic-stochastic approach. The selected GCM was HadCM3 from Hadley Centre (UK), A2 and B2 scenarios. The hydrological model selected was Sacramento (Burnash et al, 1973) with a coupled snow model, based in Snow-17 (Anderson, 1978, Muñoz, 2006). The comparison between observed data (1980-2005) and climate change scenarios using average (Osses, 2006) and individual series were used to assess the climate change scenarios performance in the gaged period. Results Analyzing the flows generated with individual series of the downscaled weather variables (temperature, rainfall and evaporation) it is possible to see a good relationship, statistical and quantitative, with the observed values (1980-2005). The flow generated with the average serie of the generated weather variables shows an overestimation of the discharge and a poor statistical relationship with the observed values (1980-2005). Conclusions The use of average input series is a poor approach to assess the water availability. Better results can be obtained using individual series of statistical downscaled weather variables. References Anderson, E. A. (1978). Snow Cover Energy Exchange. National Weather Service River Forecast System Manual and Documentation II.2.1-1, NOAA Office of Hydrology, National Weather Service, USA. Burnash, R.J.C., R.L Ferral, and R.A. McGuire (1973). A Generalized Streamflow Simulation System, Conceptual Modeling for Digital Computer. U.S. Department of Commerce, National Weather Service and State of California, Department of Water Resources, Sacramento, CA., USA. Muñoz, R. (2006). Análisis de Técnicas de Escalamiento Espacial de Variables Meteorológicas en Cuencas Nivo-pluviales utilizando el Modelo Sacramento de Simulación Hidrológica (Analysis of Meteorological Variable Scaling Techniques in Watershed with Snow and Rain Areas using Sacramento Model), Study to apply for the Civil Engineering Title, Universidad de Chile, Santiago, Chile. Osses, A. (2006). Influence of Climate Change on Drinking Water Supply from a Reservoir in Santiago, Chile. MSc Thesis, Institute for Technologies in the Tropics, University of Applied Sciences Cologne, Cologne, Germany. Wilby, R. L. and C. W. Dawson (2004). Using SDSM Version 3.1: A Decision Support Tool for the Assessment of Regional Climate Change Impacts, User Manual. Available at https://co-public.lboro.ac.uk/cocwd/SDSM/.
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