20 years of mass balances on the Piloto glacier, Las Cuevas river basin, Mendoza, Argentina

LEIVA, J.C.; G.A. CABRERA AND L.E .LENZANO

GLOBAL AND PLANETARY CHANGE

ELSEVIER

Año: 2007 p. 10 - 16

0921-8181

Abstract Climatic changes of the 20th century have altered the water cycle in the Andean basins of central Argentina. The most visible change is seen in the mountain glaciers, with loss of part of their mass due to decreasing thickness and a substantial recession in the last 100 years. This paper briefly describes the results of glacier mass balance research since 1979 in the Piloto Glacier at the Cajón del Rubio, in the headwaters of Las Cuevas River, presenting new results for the period 1997-2002. Within the 24-year period, 67% of the years show negative net annual specific balances, with a cumulative mass balance loss of -10.50 m water equivalent (w.e.). Very large interannual variability of net annual specific balance is evident, due largely to variations in winter snow accumulation, with a maximum net annual value of +151 cm w.e. and a minimum value of -230 cm w.e. Wet El Niño years are normally associated with positive net annual balances, while dry La Niña years generally result in negative balances. The glacier contribution to Las Cuevas River runoff is analysed based on the Punta de Vacas River gauge station for a hypothetical year without snow precipitation (YWSP), when the snowmelt component is zero. Extremely dry years similar to a YWSP have occurred in 1968-1969, 1969-1970 and 1996-1997. The Punta de Vacas gauge station is located 62 km downstream from Piloto Glacier, and the basin contains 3.0% of uncovered glacier ice and 3.7% of debris-covered ice. The total glacier contribution to Las Cuevas River discharge is 82±8% during extremely dry years. If glacier wastage continues at the present trend as observed during the last 2 decades, it will severly affect the water resources in the arid central Andes of Argentina. A first stage of increased glacier runoff should occur due to enhanced melting, with a subsequent stage of runoff declination. Keywords:  glacier mass balance, glacier contribution to runoff, Argentinian Central Andes