versión On-line ISSN 0717-7178
Investig. mar. v.30 n.1 supl.Symp Valparaíso ago. 2002
Drought Frequency and its Social
Impacts in the Semi-Arid Region of
Department of Environmental Sciences and Natural
Resources, University of Chile,
Santa Rosa 11, 315 - La Pintana, Santiago de Chile,
This research was aimed at characterizing some of the basic features of the precipitation regime of the Limarí River basin, exploring the relationship between precipitation anomalies and ENSO, and measuring the vulnerability to drought of a subset of the rural population living in the Comunidades Agrícolas of this basin. Another objective was to explore the effectiveness of public policies to mitigate the impacts of drought among those most vulnerable.
Results and Discussion
The Limarí River basin is located south of the southern fringe of the hyper-arid Atacama Desert in Chile, in an area that is usually considered as semi-arid. The climate in the study area is distinctly Mediterranean. In fact, 85.7 percent of the annual precipitation is concentrated in the winter (May-August), while summer is usually dry. The rainiest month of the year is July, after which precipitation decreases rapidly. Thus, the study area has a long-term annual precipitation average of 161.6 ±117.7 mm while the coefficient of variation is 0.59.
Winter precipitation in the study area is significantly correlated to Niño 3 and Niño 3+4 Sea Surface Temperature (SST). During the period 1950-1999, the study area suffered 15 severe droughts. Nonetheless, only one of them occurred during a strong La Niña event while an 86.6 percent of the extreme droughts occurred during neutral to moderate La Niña events. Overall, the study area suffered from intense droughts during thirty percent of the years of the second half of the XX Century. This figure has profound implications for both the rural households and the policy makers in the area.
The area was settled early during colonial times. Copper, gold and silver mining soon became the most important economic activities. The mining process required, however, large amounts of timber for the smelters. Agricultural activities such as wheat cropping and animal husbandry used the lands cleared by the miners. Thus, several authors have speculated that late during the XIX Century the Limarí River basin must have lost most of its natural vegetation. Many small farmers, organized in the so-called Comunidades Agrícolas, made their living from wheat cropping and goat husbandry, just as they usually do nowadays in order to ensure the subsistence of their families.
The Comunidades Agrícolas is an institutional arrangement that was put in place in the study area during the Colonisation, as a way to ensure survival of several right-holders that share common access to natural resources such as land and water in a dry environment. Nonetheless, some findings of this research indicate that allocation of these resources, after land property rights were distributed among the Comuneros, is not necessarily equitable. Sharp differences in the availability of land and water among families of the same Comunidad generate different (in)abilities to cope with extreme droughts.
Other findings point in the direction of lack of drought planning. Even though extreme droughts are frequent, local public agencies do not act proactively. Instead, a Regional Drought Commission in charge of allocating emergency funds provided by the central government is put in place while the drought lasts. This Commission disappears with the first rain. Unfortunately, most of the emergency aid is not distributed among those rural families most vulnerable.
Thus, this research proposes a methodology to measure vulnerability that can be used by local governments to determine who is more vulnerable and their spatial distribution.