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The current global climate conditions differ from the historical average data. In the Arid Chaco this trend is reflected in the advance of the agricultural frontier towards the east of the subregion, due partially to an increase in the precipitation. The aim of this paper is to analyze temporal changes of temperature and precipitation, and the ENSO influence over these variables. The historical series of the Arid Chaco climate were analyzed for six locations for the period 1931-2011. The results show positive trends in precipitation and average temperatures, although increasingly variable. Precipitations and temperature are inversely related, possibly as a result of the advance of cold fronts from the south, causing precipitation. Nevertheless, the linear regressions between both variables do not fit significantly (p<0,05). Changes in the location of high and low pressure centers in the subregion explain another part of the variation in mean annual temperatures and precipitation. Many of the observed climate anomalies coincide with ENSO events, although the intensity of these events have little relation with the intensity of climate anomalies in the subregion. [ABSTRACT FROM AUTHOR]

Climate variability (CV) and climate change (CC) have been associated to global changes or to changes in the climate regime and have shown remarkable effects on the hydrological cycle. Water shortage, changes in precipitation intensity, and variability of extreme events are gaining more importance. Because of the increase in air temperature and the changes in precipitation, CC is increasing the competition for fresh water and is impacting hydrological processes and regimes, causing in some cases a larger flow of pollutants and sediments in lakes and rivers, water quality degradation, alteration of the rate of bio-geochemical processes, and reduction of dissolved oxygen concentration. The need for adapting to CC is urgent when large economic and social changes are occurring that affect usage of water resources (WR). CC is increasing the vulnerability of badly-managed water systems, creating an urgent need to build a new framework for the management of WR. In this paper, an integrated water resource management concept (IWRM) is presented, which is gaining acceptance as a CC adaptation strategy. [ABSTRACT FROM AUTHOR]

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