Spatial and temporal variations of evapotranspiration, groundwater and
precipitation in Amazonia
Juan Zhang1, Jie Niu1, Chaopeng
Shen2, John M. Melack3, Jin
Zhang1, Han Qiu4, Bill X.
Hu1, and William J. Riley5
1Institute of Groundwater and Earth Science, Jinan
University, Guangzhou 510632, China
2Civil and Environmental Engineering, Pennsylvania
State University, PA
3Earth Research Institute, University of California,
Santa Barbara, CA
4Joint Global Change Research Institute, Pacific
Northwest National Lab, College Park, MD 20740, USA
5Earth Sciences Division, Lawrence Berkeley National
Lab, Berkeley, CA
Correspondence to: J. Niu,
jniu@jnu.edu.cn
Abstract
The relationships and seasonal-to-annual variations among
evapotranspiration (ET ), precipitation (P ), and
groundwater dynamics (total water storage anomaly, TWSA ) are
complex across the Amazon basin, especially the water and energy
limitation mechanism for ET . To analyze how ET is
controlled by P and TWSA , we used wavelet coherence
analysis to investigate the effects of P and TWSA onET at sub-basin, kilometer, regional, and whole basin scales in
the Amazon basin. The Amazon-scale averaged ET has strong
correlations with P and TWSA at the annual periodicity.
The phase lag between ET and P (\(\phi_{ET-P}\)) is
~1 to ~4 months, and between ETand TWSA (\(\phi_{ET-TWSA}\)) is ~3 to
~7 months. The phase pattern has a south-north divide
due to the significant variation in climatic conditions. The correlation
between \(\phi_{ET-P}\) and \(\phi_{ET-TWSA}\) is affected by the
aridity index, of each sub-basin, as determined using the Budyko
framework at the sub-basin level. In the southeast Amazon during a
drought year (e.g., 2010), both phases decreased, while in the
subsequent years, \(\phi_{ET-TWSA}\) increased. The area of places
where ET is limited by water continues to decrease over time in
the southern Amazon basin. These results suggest immediate strong
groundwater subsidy to ET in the following dry years in the
water-limited area of Amazon. The water storage has more control onET in the southeast but little influence in the north and
southwest after a drought. The areas of ET limited by energy or
water are switched due to the variability in weather conditions.
Running head: Evapotranspiration, groundwater and precipitation
variation in Amazon
Keywords: Evapotranspiration (ET ), Wavelet coherence,
Amazon basin, Phase lag, Budyko framework