The hydrological consequences of Eucalyptus afforestation in the Argentine Pampas

Authors: Engel, V, EG Jobbágy, M Stieglitz, M Williams, RB Jackson

The impacts of a 40 ha stand of Eucalyptus camaldulensis in the Pampas grasslands of Argentina were explored for two years using a novel combination of sap flow, groundwater data, soil moisture measurements, and modeling. Sap flow measurements showed transpiration rates of 2 to 3.7 mm d-1, lowering groundwater levels by more than 0.5 m with respect to the surrounding grassland. This hydraulic gradient induced flow from the grassland areas and resulted in nighttime rising of the plantation water table. Groundwater use estimated from diurnal water table fluctuations correlated well with sap flow (p < 0.001, r2 = 0.78). Differences between daily sap flow and the estimates of groundwater use were proportional to surface soil moisture content (p<0.001, r2 = 0.75). E. camaldulensis therefore used both groundwater and vadose zone moisture sources, depending on soil water availability. Model results suggest that groundwater sources represented ~67% of total annual water use.
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