Recent rainfall and runoff variability in central Argentina

Laguna Mar Chiquita, a closed, shallow, hypersaline lake in central Argentina (∼30–31°S, 62–63°W), is a sensitive marker of high- and low-frequency changes in regional hydrology and, therefore, of climatic changes at middle latitudes in southeastern South America. Its drainage basin and neighboring areas, including the Sierras Pampeanas de Córdoba, and Sierra del Aconquija (27–33°S, 62–66°W), are under the influence of diverse climate drivers that determine a complex behavior in rainfall and runoff dynamics. Statistical (Mann–Kendall and seasonal Kendall trend tests) and spectral analyses (Fourier and wavelet transform) of the available data show that: (a) there is significant evidence that rainfall has increased in the region since the 2nd half of the 20th century; (b) concurrently, runoff has also increased, particularly in the northern tributaries (north of 31°S) of Mar Chiquita; (c) northern rainfall and discharge records mostly exhibit an apparent near-decadal (also near-bidecadal in runoff) climatic signature; and d) the ENSO influence on rainfall appears faint but discernible in the southern (south of ∼31°S) portion.