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Remote Sens. 2014, 6(7), 5885-5908; doi:10.3390/rs6075885

Evapotranspiration Variability and Its Association with Vegetation Dynamics in the Nile Basin, 2002–2011

1
Geospatial Sciences Center of Excellence (GSCE), South Dakota State University, Brookings, 57007 SD, USA
2
Earth Resources Observation and Science (EROS) Center, U.S. Geological Survey, Sioux Falls, 57198 SD, USA
*
Author to whom correspondence should be addressed.
Received: 13 January 2014 / Revised: 12 June 2014 / Accepted: 16 June 2014 / Published: 25 June 2014
(This article belongs to the Special Issue Earth Observation for Water Resource Management in Africa)
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Abstract

Evapotranspiration (ET) is a vital component in land-atmosphere interactions. In drylands, over 90% of annual rainfall evaporates. The Nile Basin in Africa is about 42% dryland in a region experiencing rapid population growth and development. The relationship of ET with climate, vegetation and land cover in the basin during 2002–2011 is analyzed using thermal-based Simplified Surface Energy Balance Operational (SSEBop) ET, Normalized Difference Vegetation Index (NDVI)-based MODIS Terrestrial (MOD16) ET, MODIS-derived NDVI as a proxy for vegetation productivity and rainfall from Tropical Rainfall Measuring Mission (TRMM). Interannual variability and trends are analyzed using established statistical methods. Analysis based on thermal-based ET revealed that >50% of the study area exhibited negative ET anomalies for 7 years (2009, driest), while >60% exhibited positive ET anomalies for 3 years (2007, wettest). NDVI-based monthly ET correlated strongly (r > 0.77) with vegetation than thermal-based ET (0.52 < r < 0.73) at p < 0.001. Climate-zone averaged thermal-based ET anomalies positively correlated (r = 0.6, p < 0.05) with rainfall in 4 of the 9 investigated climate zones. Thermal-based and NDVI-based ET estimates revealed minor discrepancies over rainfed croplands (60 mm/yr higher for thermal-based ET), but a significant divergence over wetlands (440 mm/yr higher for thermal-based ET). Only 5% of the study area exhibited statistically significant trends in ET. View Full-Text
Keywords: evapotranspiration; vegetation productivity; NDVI; land cover; climate; rainfall; trend analysis; Nile Basin evapotranspiration; vegetation productivity; NDVI; land cover; climate; rainfall; trend analysis; Nile Basin
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MDPI and ACS Style

Alemu, H.; Senay, G.B.; Kaptue, A.T.; Kovalskyy, V. Evapotranspiration Variability and Its Association with Vegetation Dynamics in the Nile Basin, 2002–2011. Remote Sens. 2014, 6, 5885-5908.

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