Determinación de campos areales de precipitación y evapotranspiración en la margen izquierda de la cuenca del Paraná en territorio de Argentina. I: polígonos de Thiessen y kriging

Abstract

Precipitation (P) and potential evapotranspiration (ETP) are terms of the water balance equation that are at the catchment scale. This work presents results of precipitations and evapotranspiration estimations obtained by interpolations performed both by Thiessen polygons and the kriging geostatistical technique; the study involves catchments located at the left bank of the Paraná river, within Argentinean territory, having discharge records. Thus, twelve catchments located in the provinces of Misiones, Corrientes and Entre Ríos have been studied. For this purpose, the available meteorological data sets recorded during a common period of time, i.e. between 1970 and 2010, within the perimeter and in the external neighbourhood of each catchment have been used. Before assessing average precipitation and ETP of the domain areas nonexistent monthly data were approximated form neighbour stations. Then, the spatial contribution of each measurement site to the areal domain has been weighted. Monthly precipitation and ETP showed spatial dependency that was modelled by linear and Gaussian semivariograms, respectively. In comparison with the Thiessen polygon methods, ordinary kriging provided lower areal domain estimates of precipitation in 11 out of the 12 basins studied catchments, and the higher differences were observed at those of the Misiones province. It was concluded that increasing the complexity of the method used for estimating areal precipitation or ETP shows no evidence of better estimates of these variables.