The great drought of 1968-69 in the Cordillera de los Andes. Impacts and responses.

PRIETO M. R.; ARANEO D. C.; VILLALBA R.

Valdivia, Chile

Otro; Third Science Meeting, IAI Collaborative Research Network 2047.; 2010

IAI

The increased frequency of extreme droughts in the Andes Cordillera over the last 100 years has also been associated with a greater demand for water for domestic use, irrigation and energy production. The constantly increasing population further heightens the hazard associated with these events. In addition, the extraordinary recession of glaciers over this period also reduces the capacity for regulation of Andean streamflows in times of shortage. The present work studies the extreme drought event of 1968-69 in the Argentinean Central Andes using historical documentation, tree rings and meteorological records. This case study leads to an appreciation of the significant impact produced by water shortages during the spring-summer period of those years. This is particularly true for a province such as Mendoza in which agricultural, economic and daily life depends on the flow of rivers originating from the eastern flanks of the Andes Cordillera. The results of this study could be useful in establishing guidelines for political actions to prevent or at least, alleviate the effects of similar future droughts. However, the significant population increase in Mendoza since the 1968-69 drought and the present infrastructure problems related to usage of the water resource would further exacerbate these effects. The critical situation reported by the newspapers of 1967-68 and 1968-69 related to the scarcity of snow in the cordillera and the reduction of glacier melt due to the relatively low temperatures during the spring of those years. This led to lower discharge in the provincial rivers and in the groundwater, reducing water availability for agriculture. It also produced an electrical energy shortage because of the lack of water for the generating hydro plant on the Atuel River. This led to dynamiting of the snow-ice meltwater-fed Atuel lake to lower its level and release water for power generation downstream on the Atuel River. We also examine the consequences of the water shortage through the economic and energy data from the Direccion de Estadísticas of the Province of Mendoza as related to surface and groundwater resources, plus impacts on wetland environments, agricultural production and population. The 1968 - 69 drought was an event of great intensity and complexity that severely affected the water available for irrigation, water use in the city of Mendoza and electric power generation in the Atuel river. Similar droughts in the 40´s and 50´s, did not result in scale of reporting seen during the 1968 - 69 event. We believe that the impact was larger because, prior to 1958, when the first hydroelectric plant started on the Atuel River, the energy in Mendoza was mainly obtained by thermal generation and through small power plants. The local press emphasized the dwindling streamflow because of the alarms raised during November and December 1968 by the problems of reduced electric power generation. These alarms continued in January, February and March of 1969 because of water shortages for agricultural production, that dropped 30 and 40% in that year. These observations lead to consideration of the potential consequences of a similar event in the future. Even though the cultivated area and agricultural water demands might be similar, the population of Mendoza has more than doubled and the energy demand for domestic and industrial consumption is considerably larger than in 1968. We concluded that the there has been an exponential increase in the vulnerability of the Mendoza population to drought and that it will continue to increase in the future.