Distribución espacial y controles ambientales de las represas (tajamares) en el Chaco Árido

Abstract

Arid regions are characterized by water shortage throughout the year, which constrains both the vegetation growth and the supply of water for livestock consumption. The Arid Chaco (~10 Mha) hosts extensive and low-investment livestock systems based on rainwater harvesting stored in dams (small impoundments) as the main source of water supply. In this study, we characterized the spatial distribution of dams in the Arid Chaco and analyzed their relationship with biophysical variables (e.g. rainfall, vegetation, roads). For these purposes, we used satellite images, vector information and performed multivariate analysis on a spatial grid of 135 cells of 0.25°x0.25°. In total, 7920 dams were identified (1 dam every 1230 ha), with maximum densities of 1 dam every 185 ha but also cells without dams associated with the presence of mountains, salt flats and dunes. Dam density was higher in cells with higher densities of livestock establishments, roads and cattle stock (r=0.63, r=0.56 and r=0.51, respectively; P<0.01 in all cases), and in cells with higher mean annual rainfall and lower interannual rainfall variability (r=0.62 and r=-0.47, respectively; P<0.01 for both cases). Although the mean annual rainfall was the best-associated variable with the distribution of dams at the regional scale, this relationship weakened towards the extremes of the gradient (arid and sub-humid). This may be due to anthropic factors such as the low profitability of livestock systems, the previous land uses or land-use changes. The results of this study represent a first attempt to assess the importance of impoundments in the Arid Chaco. We believe that this study may be useful not only to understand livestock production, but also for future studies related to the conservation of wildlife and the development of rural towns in the region.