Disentangling a century of water harvesting development in the Paraguayan dry Chaco flatlands

Abstract

Improving water harvesting in flat drylands is one of the great challenges that humanity will face in the coming years. Based on a remote sensing approach, we mapped and determined the drivers of water harvesting systems (ponds of ~1 ha) distribution in the Mennonite colonies of the Paraguayan Chaco. A total of 59,251 ponds were detected. The average pond density was one for every 4 km², showing a very heterogeneous spatial distribution (14% of the sampled territory has no ponds). Pond density was mainly explained by mean annual precipitation (36.01% of increment in MSE), while soil variables (slope, texture) showed no explanatory power. Our findings show that the decision on where to build ponds is strategically made based on production development needs, without considering the environment's natural capacity to "generate water" (catchment areas). This ability makes water harvesting in the Paraguayan Chaco as interesting as unique in the world.