期刊
WATER RESOURCES RESEARCH
卷 52, 期 2, 页码 644-659出版社
AMER GEOPHYSICAL UNION
DOI: 10.1002/2015WR017251
关键词
evapotranspiration; upper Blue Nile; hydrological data assimilation; hydrology
资金
- Masdar Institute of Science and Technology (Masdar Institute), Abu Dhabi, UAE [02/MI/MIT/CP/11/07633/GEN/G/00]
- Massachusetts Institute of Technology (MIT), Cambridge, MA, USA [02/MI/MIT/CP/11/07633/GEN/G/00]
Reliable estimates of regional evapotranspiration are necessary to improve water resources management and planning. However, direct measurements of evaporation are expensive and difficult to obtain. Some of the difficulties are illustrated in a comparison of several satellite-based estimates of evapotranspiration for the Upper Blue Nile (UBN) basin in Ethiopia. These estimates disagree both temporally and spatially. All the available data products underestimate evapotranspiration leading to basin-scale mass balance errors on the order of 35 percent of the mean annual rainfall. This paper presents a methodology that combines satellite observations of rainfall, terrestrial water storage as well as river-flow gauge measurements to estimate actual evapotranspiration over the UBN basin. The estimates derived from these inputs are constrained using a one-layer soil water balance and routing model. Our results describe physically consistent long-term spatial and temporal distributions of key hydrologic variables, including rainfall, evapotranspiration, and river-flow. We estimate an annual evapotranspiration over the UBN basin of about 2.55 mm per day. Spatial and temporal evapotranspiration trends are revealed by dividing the basin into smaller subbasins. The methodology described here is applicable to other basins with limited observational coverage that are facing similar future challenges of water scarcity and climate change.
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