Resumo

LAURO, Carolina; VICH, Alberto  e  MOREIRAS, Stella Maris. Streamflow variability of river basins from Cuyo region. Geoacta [online]. 2015, vol.40, n.2, pp.28-51. ISSN 1852-7744.

Detecting trend and step changes in hydrological variables is important issue if we want to evaluate climate variability in Cuyo river systems which are essential for water resources management. The aim of this article is to detect changes of fluvial regime in basins from Mendoza and San Juan province (Cuyo region). We worked with data from 23 gauge stations between 31º y 35º S. First we made an exploratory data analysis, then we applied parametric and non parametric tests for detecting trends and step changes. We analyzed 19 hydrological variables with 95% level of significance. As a result we find that 73% of variables analyzed are not normally distributed, and neither they are independent and random. The outliers found are consistent with years of occurrence of ENSO events. 76% of the analyzed variables showed no significant trends, 26% showed positive trends and 1.2 % negative. The increasing trends were found in minimum, or winter flows variables. On the other hand, the decreasing trends found were associated with maximum or summer flows. 58% of detected step changes were positive while 9% were negative. Step changes were detected mostly during the 70s and were positive. In the 50s the detected jumps detected were negative. Positive and negative jumps were found in the 80 and 90. While in the last decade were the positive. The lack of homogeneity in flow series could be due to multiple factors, whether natural or anthropogenic origin. The basins studied have low human intervention, so the changes detected are more likely to arise from variation in climate.

Palavras-chave : Hydrological variables; Trend; Step change; Cuyo.

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