This work estimates evapotranspiration and other
surface energy balance variables from four ecosystems
with different water use strategies in the protected area
of Doñana (Spain) along two years with contrasting
precipitation levels. During 2004/05 annual rainfall was
reduced by 75% with respect to the previous year.
Fluxes were derived from MODIS thermal and
reflectance data for 8-day periods using two modelling
approaches. Results showed that both of the approaches
detected drought impacts on ecosystem fluxes.
However, the method based on a dryness index derived
from the trapezoid formed by Ts and the vegetation
index (EVI) performed better than the surface–
resistance approach. According to our results, the most
vulnerable to the drought event were marshes and
xerophytic shrublands while pine forests and
phreatophytic shrublands remained almost unaffected as
they can access phreatic water as indicated by
evapotranspiration/precipitation ratios exceeding 3 in
the dry year.