The dynamics of cultivation and floods in arable lands of central Argentina

Abstract

Abstract. Although floods in watersheds have been associated with land-use change since ancient times, the dynamics of flooding is still incompletely understood. In this paper we explored the relations between rainfall, groundwater level, and cultivation to explain the dynamics of floods in the extremely flat and valuable arable lands of the Quinto river watershed, in central Argentina. The analysis involved an area of 12.4 million hectare during a 26-y period (1978–2003), which comprised two extensive flooding episodes in 1983–1988 and 1996–2003. Supported by information from surveys as well as field and remote sensing measurements, we explored the correlation among precipitation, groundwater levels, flooded area and land use. Flood extension was associated to the dynamics of groundwater level, but these two variables displayed a poor association with rainfall, being particularly decoupled from it during the rainy periods. Correlations between groundwater level and flood extension were positive in all cases, but while highly significant relations (P<0.01) were found in highlands, non significant relations (P>0.05) predominate in lowlands. Our analysis supports the existence of a cyclic mechanism driven by the reciprocal influence between cultivation and groundwater levels in highlands. This cycle would involve the following stages: (a) cultivation boosts the elevation of groundwater levels through decreased evapotranspiration; (b) as groundwater level rises, floods spread causing a decline of land cultivation; (c) flooding propitiates higher evapotranspiration favouring its own retraction; (d) cultivation expands following the retreat of floods. Thus, cultivation would trigger a destabilizing feedback self affecting future cultivation in the highlands. It is unlikely that such sequence can work in lowlands. The results suggest that rather than responding directly and solely to the same mechanism, floods in lowlands may be the combined result of various factors like local rainfall, groundwater level fluctuations, surface and subsurface lateral flow, and water-body interlinking. Although the hypothetical mechanisms proposed here require additional understanding efforts, they suggest a promising avenue of environmental management in which cultivation could be steered in the region to smooth the undesirable impacts of floods.

Trade‐offs in water and carbon ecosystem services with land‐use changes in grasslands

“…In contrast, the Argentinean agro‐pastoral system may currently be experiencing a lose–lose scenario under market pressures to cultivate rain‐fed crops in the productive humid Pampas (Viglizzo et al. ), increasing flooding risks while driving livestock production to the marginal drier grasslands and potentially increasing woody plant dominance in the drier grasslands (Archer ).…”

Climate change in Argentina: trends, projections, impacts and adaptation

“…In the Espinal, an ecoregion of the Chaco‐Pampean plains, 20% of ecosystems were lost and 60% of the forests were removed between 1987 and 2009 . In the Pampa region, flood extension has been associated with the dynamics of groundwater levels that have been influenced by precipitation and land‐use change . In addition, the disappearance of natural and semi‐natural habitats in these heavily transformed agricultural landscapes will have substantial negative effects on the provision of natural pest control services …”

Surface moisture area during rainfall–run‐off events to understand the hydrological dynamics of a basin in a plain region

“…At a local scale, the basin is characterized by the coexistence of a small gently hilly area with a neighbouring flat landscape which causes a particular hydrological behaviour. The hydrological dynamics at this and other comparable plain areas around the world (e.g., Brazilian Pantanal, Orinoco Llanos in Colombia and Venezuela, the plains of Manitoba and Saskatchewan in Canada, the plains at the east of Europe and Western Siberia, and those located at the east of Australia, among others) is complex and needs further research and investigation because its understanding is still not complete (Aragón et al, ; Dalponte et al, ; Jobbágy, Nosetto, Santoni, & Baldi, ; Scioli, ; Viglizzo et al, ). This manuscript discusses the relationships between remote sensed SMA, and a set of hydrological variables registered or calculated during rainfall–run‐off events in the watershed, on a daily basis.…”