Basis to study the alterations of the hydrological regime and its ecological importance in Argentina

In this work, we propose the bases for assessing the ecohydrological changes resulting from direct and indirect human activities at a regional scale in Argentina. The climatic, morphological and geological diversity of the territory is manifested in different ecoregions and in a high diversity of lotic and lentic environments which are closely linked to the water systems. Daily flows, groundwater levels, flooded surfaces or hydrometric heights have different influences depending on the ecoregion considered in each water system. The historical hydrological information with continuity and records with a sufficient extension for the analysis of the alterations of the hydrological regime are relatively scarce and restricted to 163 measuring stations. The application of a conceptual model for the analysis of hydrological alterations is proposed, followed by the study of temporal variations in the hydrological and morphological conditions prior to the anthropic activity (pre-impact), to then consider the new hydrological-ecological situation (post-impact), on the basis of which appropriate measures should be adopted to mitigate the ecological damage when they occur. Although there are various methodologies to conduct this analysis, considering the availability of current data in Argentina, we propose the use of the methodological framework based on the ELOHA (Ecological Limit of Hydrological Alteration) concept for the analysis of hydrological alterations. Although the holistic method provides the best results and the least uncertainty, considering the heterogeneity, scarcity and lack of continuity of hydrological records at a general level, the proposed technique could be a good approximation at a regional scale. It is concluded that it will be necessary to adapt the methodological bases and analysis techniques to this condition in order to create a database for the strategic planning of water resources in Argentina.