Resumo

VILLANUEVA-DIAZ, José et al. Hydroclimate variability reconstructed with tree rings for the Lerma Chapala basin in Guanajuato. Tecnol. cienc. agua [online]. 2012, vol.3, n.4, pp.05-26. ISSN 2007-2422.

A historic understanding of climate is essential to determine its long-term variability and trends. Six tree-ring chronologies covering roughly 250 years were developed for the Lerma Chapala basin, in the states of Guanajuato, Jalisco and Queretaro. Two species were used for this purpose, Taxodium mucronatum and Pinus cembroides. For the central-southern region of Guanajuato, one seasonal winter-spring (January-June) precipitation reconstruction was developed for the period 1770-2007, and for the northwestern section two were generated--one for the period March-September, extending back 208 years (1790-2007) and an annual reconstruction (January-December) covering 158 years. Severe hydroclimatic events were present in the reconstructions, as reported by historical records, including those producing grain scarcity, famine, epidemic outbreaks, migrations, as well as other disasters such as droughts in the 1860s, 1890s, 1920s, 1950s, 1970s, and 1990s. These serve to verify the reliability of the reconstructions. A historical analysis of ENSO and its impact on precipitation, ring width indices, and rainfed crop production was very inconsistent and only severe ENSO events affecting precipitation in Guanajuato were detected. This behavior indicates the need to more thoroughly investigate other climatic variables that, in addition to the ENSO phenomenon, may explain the hydroclimate variability in this region.

Palavras-chave : Guanajuato; Lerma Chapala; dendrochronology; ring width index; reconstructed precipitation; hydroclimate variability; ENSO; droughts.