CONICET | Buscador de Institutos y Recursos Humanos

The Atuel River fluvial system (ARFS; ~34°30´S-70°09?W, ~37°30´S-67°00?W) is located in central-west Argentina, in the South American Arid Diagonal (~200 mm/year rainfall). Its perennial seasonal-regime flow originates from snowfall ablation in the Andes Cordillera catchment mountain area. At the extra-andean lands, the middle basin is a transporting zone formed by a proximal piedmont with alluvial fans, and to the east, by a main trunk stream (MTS) crossing the San Rafael tectonic block. In the AR lower basin, the MTS bifurcates into a distributary drainage network formed by many meandering streams flowing along the Depresión de la Travesía plain and disappearing into a terminal wetland area. The AR lower basin alluvial sedimentary record consists of three main morphological units: a Regional Aggradational Plain (late Pleistocene- early Holocene), a fill terrace (middle and late Holocene), and a present floodplain (≤ ca. 400 yr BP.).Today, the ARFS is a ?misfit? fluvial system compared with the previous glacial-stage flows. In addition, on the 40?s started the construction of a series of dams at the AR transporting reach affecting the lower basin fluvial regime which uppermost part turned into an agricultural irrigated oasis in detriment of the terminal wetland area. At the lower basin the fluvial network was also modified by channel constructions to derivate water for irrigation, and soils became strongly salinized. As a result, the present active surface runoff zone in the lower basin and particularly at the wetland area has a minimum expression, it is restricted to channel, marshes, and crevasse splays of the Arroyo de La Barda, the only present-day active channel. Consequently, this extreme misfit condition in the AR lower basin conducted to a major socio-economic impoverishment of this arid land historically used by local people for agricultural-livestock activities, and now totally diminished and restricted to subsistence livestock farming.