Evolution of annual soil water surplus in Pampean Region (Argentina)

Floods are a constant in the central eastern region of Argentina as well as droughts. Almost every year, one of these two extreme hydrologic events takes place and sometimes, both of them. The temporal evolution of soil water surplus, during sixty years, is studied in nine meteorological stations. These are located in important areas whose land uses have economic and social impact. They are localized in the provinces of Cordoba, Santa Fe, Entre Rfos province, La Pampa and Buenos Aires. Daily meteorological data were provided by the National Meteorological Service and the period considered was 1951-2010. Soil water balance was performed according the model used Forte Lay et al. which is based on Thornthwaite-Mather method and the normal daily mean reference evapotranspiration was estimated by the Penman-Monteith formula. In the present paper the parameter soil water surplus is used as an index of flood risk. Makesens methodology was used for the statistical analysis; this is based in non parametric test Mann-Kendall for the trend study and the non parametric method Sen for the magnitude. All the analyzed stations showed different evolution of soil water surplus and have experienced flood risk in some moment of the studied period.