Ion and isotope chemistry as indicators of different geographic regions and water sources to the upper Mendoza river basin, Central Andes of Argentina.

CRESPO SEBASTIAN; ARANIBAR JULIETA; GOMEZ LAURA; SCHWIKOWSKI MARGIT; BRUETSCH SABINA; CARA LEANDRO

San Rafael

Encuentro; IAI CRN 2047B Documenting, understanding and projecting changes in the hydrological cycle in the American Cordillera.; 2014

Inter American Institute, Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales

The Mendoza River, located in the North of Mendoza province (Argentina) yields an average of 47m3/s, and provides water for domestic use, irrigation, industry, and hydroelectric energy generation for more than 1 million inhabitants. This water supply is mainly dependent on snow and ice melt from the Andes. Climate change may modify spatial and seasonal patterns of precipitation and glacier melt, so it is important to quantify the contributions of each source to the river flow. We propose that differences in precipitation systems, geology, and sediment contact times of different sources and recharge areas provide chemical and stable isotope signatures to the water, allowing the identification of its geographic and hydrogeologic origin. In these latitudes (~33ºS), the Andes present two main mountain ranges with North-South direction, which receive different contributions of precipitation from Atlantic and Pacific moisture sources: Cordillera Frontal and Cordillera Principal. Water from both mountain ranges had different stable isotope and ion chemistry. Water derived from different ice bodies, snow, and groundwater also differed on either stable isotope or ion composition. This study indicates that it is possible to identify the contribution of precipitation from different geographic areas (Cordillera Principal and Cordillera Frontal) and water sources (groundwater, glacier, debris covered glacier and rock glacier) to the streams of the Mendoza river basin.