Preliminary studies of water, snow and ice in the Quebrada del Medio, Hans Stepanek rock glacier, Mendoza, Argentina

SILEO NOELIA; TROMBOTTO LIAUDAT DARÍO; DAPEÑA, CRISTINA; BODIN, XAVIER; MARCOSIG, IVANNA; TABOADA, NICOLÁS A.

Postdam

Congreso; XI INTERNATIONAL CONFERENCE ON PERMAFROST 2016; 2016

International Permafrost Association

This paper intends to give some insights into the hydro-geochemical behavior of groundw ater and surface w ater related to glaciers, covered glaciers and rock glaciers in the Vallecitos River basin. The goal of our study is to characterize different w ater origins and their hydrogeochemical composition in a typical cryogenic environment. The basin includes permafrost in situ as w ell as temporary and perennial snow patches. It also aims at understanding the dynamics of w ater w ithin the cryogenic system, in particular inside the rock glaciers, in order to determine potential reservoirs of fresh w ater for the local population. The study area is located betw een 69º 22 ´and 69º 25´ W and 32º 56 ´and 32º 58´ S, in the Cordón del Plata range, Cordillera Frontal, Mendoza, Argentina. The highest peaks in this region the summit of Cerro Rincón. A netw ork of surface w ater sampling has been set up w ith the main points corresponding to springs, streams and the Vallecitos River, together w ith sampling points for seasonal snow patches and ice. A rain collector for isotope samples recording of any event has been installed, in order to generate a local meteoric w ater register. The first results reveal several differences betw een the three main sub- basins of the Vallecitos River basin. Different w ater sources and circulation patterns can be identified w hich are reflected in the hydrogeochemical and isotopic results (Sileo et al., 2015). Among the studied sampling points (Van06 and Vmn07) in this region, a temperature drop from 5 ºC to2.6 ºC, a pH rise from 5.5 to 7.5, and variations in the concentrations of Zn, Cd, Ni, Mn and Si in relation to different altitudes are observed. Betw een the mentioned tw o points there is a horizontal distance of 800 m, w here the stream flow s underground, flow ing (apparently)through the active rock glacier nose and changing its physical and chemical properties (Fig. 1). The decline of the toxic values of Ni at Vmn07, in comparison to higher values at higher altitude, found at the bottom of the cryoform gives it a special significance in terms of hydrochemical periglacial processes associated to some particular chemical elements, because something occurs for the retention of elements in its internal sedimentary structure. Furthermore, other underground w ater inputs from other sources, such as sub-superficial melting w ater of parts of the rock glacier can explain physico- chemical phenomena at lower altitudes and they should not be discarded. In 2015, geodetic GPS measurements and terrestrial photogrammetric survey detected movements of the active layer, which appear to express internal changes of its cryogenic structure (Bodin and Trombotto, 2015).