INVESTIGADORES
ARAGON Myriam Roxana
artículos
Título:
The dynamics of cultivation and floods in arable lands of Central Argentina
Autor/es:
ERNESTO VIGLIZZO; ESTEBAN JOBBAGY; LORENA CARREÑO; FEDERICO FRANK; ROXANA ARAGÓN; L. DE ORO; VERONICA SALVADOR
Revista:
Hydrology and Earth System Sciences Discussions
Referencias:
Año: 2008 vol. 5 p. 2519 - 2545
Resumen:
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 (19782003), which comprised two extensive flooding episodes
in 19831988 and 19962003. Supported by information from surveys as well as field
and remote sensing measurements, we explored the correlation among precipitation,
10 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 re
lations (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.