IANIGLA   20881
INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Quantifying changes (gradual and abrupt) in the hydrologic regime of the cordilleran basin
Autor/es:
VICH, ALBERTO I. J.; BIZZOTTO, FEDERICO; VACCARINO, EMILCE; CORREAS, MARIANA; MANDUCA, FLORENCIA
Lugar:
Santiago de Chile
Reunión:
Congreso; UGI 2011 Regional Geographic Conference; 2011
Institución organizadora:
Unión Geográfica Internacional (UGI) y el Instituto Geográgico Militar (IGM)
Resumen:
The Andes cordillera constitutes the main regulating system of the water cycle at continental scale and there are numerous evidences that it is experiencing important environmental transformations, associated to changes in climatic conditions. This work attempts bettering the knowledge of the water offer and evaluating the impact of the climatic change over the superficial water resources in some basins, which headwaters are at the Andes cordillera and hills of the Argentine west, in a wide latitudinal gradient. The work was done detecting abrupt changes and long term trends in the runoff regime.  We analyzed 29 gauging stations and we determined 22 flow volume variables. The methodology we used is based on parametric (Student t)  and non-parametric (SROC, Mann-Kendall and corrections) tests. Both afforded similar results for a 5% signification level. Of the 629 temporal series analyzed we detected changes in   194  series with changes in the parametric trends and 165 series with changes in non-parametric trends, most of them corresponding to the low water periods.  Results show a high degree of uncertainty if the analyzed series do not comply with the conditions of normality, independence and randomness, according to the method applied. Said conditions were verified, with the first one fulfilling only 37% of the cases and the other two conditions 63% and 67% respectively. The different methods to determine abrupt changes in the hydrologic variables series show relatively different results. The different tests require the condition of distribution normality (Pettitt, Students sequential t, Worsley, Buishand). These are aspects that occur in only a few cases thus introducing a significant uncertainty level in the results. The Pettitt test did not identify abrupt changes in practically none of the analyzed series. The Worsley test is quite limited as it requires records with more than 50 observations. Generally the Student Sequential t test points at statistically meaningful breaking points more frequently than other tests. Notwithstanding, many times there are multiple leaps that none of the used tests identifies.. The breaking point usually happens in the 70's,but the series are not very extended.
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