CONICET | Buscador de Institutos y Recursos Humanos

Rainwater harvesting (RWH) has been essential for the establishment of human settlements in many dryregions of the world that lacked suitable surface or groundwater resources. A vast fraction of the SouthAmerican Dry Chaco ecoregion still relies on RWH to support, not only livestock production, but domesticand industrial uses as well. As a result, water capture and storage infrastructure is widely disseminatedthroughout the region. In this paper we characterized the most typical RWH systems in two contrastinglydeveloped sub-regions of Dry Chaco, ranging from extensive ranching to intensive beef and dairy production(central Argentina and western Paraguay, respectively). In each sub-region, we quantified RWHsystems density, spatial distribution and associations with landscape features; furthermore, we illustratedhow the daily dynamic of water stock in a typical RWH system contributes to assess their captureand storage efficiency. We found that randomly distributed low sophisticated RWH systems prevailed incentral Argentina, while clustered distributed high sophisticated ones were more common in westernParaguay. RWH systems density was ten times higher in western Paraguay (0.94 vs. 0.098 units/km2),showing an exponential association with land cleared fraction and proximity to villages. The daily dynamicof water stock of the RWH impoundment showed that water harvest events were exponentiallyassociated with precipitation magnitude events (R2 ¼ 0.86), while annual water losses were explained byinfiltration and evaporation fluxes (59 vs. 41%, respectively). Across both sub-regions, RWH accounts forless than 1% of the annual precipitation, playing a minor role on the regional water balance; however at alocal level, they can affect several hydrological fluxes including the onset of groundwater recharge andthe mitigation of extreme runoff events.©