Distribución de la precipitación y la evapotranspiración en territorio argentino de Cuenca del Plata

Abstract

Land management and land use planning need a sound knowledge of the available natural resources, and water is one of the most important of these resources. Accurate determination of the water balance and available water for different uses requires a rather dense network of hydrometeorological measurements. Precipitation (P) and potential evapotranspiration (ETP) are two terms of the water balance of major research interest in several disciplines, including Hydrology, Climatology and Agronomy. Meteorological station networks provide P and ETP data, which are commonly used for interpolation. This study analyses the spatial and temporal distribution of P and ETP on the Argentina territory of the La Plata basin. The analysis covers the 1970-2010 period and the data sets studied were provided by the National Water Resources Authority (SSRH), National Meteorological Service (SMN) and National Agricultural Technology Institute (INTA). The study was conducted both, at the annual and monthly temporal scales. Missing data were estimated using conventional methods. Pluviometry was available for 94 locations, while ETP was estimated from meteorological data at 38 weather stations using the Penman-Monteith method. The results showed specific trends for the spatial and temporal distribution of P and ETP. Average annual rainfall ranged from 499 mm to 2077 mm. Most of the studied area of the La Plata basin in Argentina is lowlands or plains, where P shows a strong trend to increase from east to west; however to the west of the plains, in Andes region, P may increase with altitude. Average annual ETP ranged from 899 mm to 1719 mm. Roughly, ETP decreases as P increases, even if there is not a total overlap of maxima and minima values of these two variables. Subsequently, the Chaco Seco region located to west of the plains ETP becomes higher than P. Analysis of temporal variability of yearly rainfall in the period 1970-2010 showed a clear increasing trend from 1970s to 2000, followed by a modest decreasing trend between 2000 and 2010. The information obtained in this study is highly important for water resource management and allocation planning, hydrological modelling, recharge assessment, and irrigation scheduling.