1a.Objectives (from AD-416):
To develop and evaluate a decision support tool for water management in the Nile River basin, using a combination of water balance modeling and remote sensing of evapotranspiration.
1b.Approach (from AD-416):
Generate and evaluate remote sensing estimates of evapotranspiration (ET) and surface moisture stress (drought) over the Nile River Basin. In collaboration with NASA scientists, use remotely sensed ET to validate hydrologic predictions from the NASA Land Data Assimilation System (LDAS), customized to operate over the Basin, and to constrain assumptions of water diversion along the Nile. The validated LDAS output will then be integrated into the existing Nile Forecast System (NSF) and Nile Basin Decision Support System (NBDSS) and used for flood warning, reservoir management, and irrigation planning.
Under this project, a time-series of maps of evapotranspiration (ET) generated using thermal satellite imagery are being generated over the Nile River Basin for integration into a hydrologic model, used to constrain estimates of water diversion in support of irrigated agriculture. Daily maps of ET at 6 km resolution have been generated using the Atmosphere-Land Exchange Inverse (ALEXI) energy balance model for 2007-2010. Monthly satellite-based ET agrees well with hydrologic model output, but additionally identifies enhanced ET over the irrigated Nile Delta, and over the Sudd Wetland.
Quantitative comparisons have been conducted between surface flux estimates from ALEXI and estimates from a prognostic land-surface model, computed using principles of water balance. In areas of limited ground validation data, comparisons between independent modeling techniques provide some basis for identifying model strengths and deficiencies. The remotely sensed ET estimates from ALEXI are being used to improve irrigation modeling components in the water balance model.