Autumn soil water surplus during ENSO events in argentine pampean flatlands

Abstract

The main argentine agricultural region (840,000 km2) is located in the pampean flatlands of Buenos Aires, Santa Fe, Córdoba, La Pampa, San Luis and Entre Ríos provinces. Differing phases of ENSO (El Niño and La Niña) have differing impacts on soil moisture conditions across the study area. Daily soil water balances are estimated for the period 1961 - 2003 using records from 76 meteorological stations, and the daily soil water surplus is employed as the major output in the present paper. The sum of autumn soil water surpluses (March, April and May) is analysed, because they are those that have more harmful effects on the crop of the cultivations of the precedent summer and also partially control the risk of floods in the important agriculture and urban areas. Moreover, these months represent the highest soil water surplus values of the year. ENSO events are identified using the multivariate index (MEI). The probabilities of occurrence of predetermined soil water surplus and hence risk are calculated and mapped. The south and south-western areas are generally free of risk during all ENSO events, while the north-eastern area (Santa Fe, Entre Ríos and north-eastern of Buenos Aires) reveal high risks of saturated soils and floods during autumn especially during El Niño years.