Browsing by Author "Aberra, Debele"

Now showing 1 - 1 of 1
  • No Thumbnail Available
    Item
    Estimation of Actual Evapotranspiration and its Impacts on Rainfed Agricultural Productivity Using Geospatial Tools in the Main Ethiopian Rift
    (Addis Ababa Universty, 2012-06) Aberra, Debele; Ayenew, Tenalem (Professor)
    Remote sensing based estimation of spatiotemporal patterns of vegetation water use has played significant roles in evaluation and monitoring of rainfed agriculture. Agriculture is the most vulnerable and sensitive sector that is seriously affected by the impact of climate variability and change, which is usually manifested through rainfall variability and recurrent drought in the Main Ethiopian Rift. The objective of this study is to estimate actual evapotranspiration for crop performance evaluation and monitoring for the study periods of 2001-2010 cropping seasons (June-September). Using VegET model that integrates commonly used water balance algorithms with remotely sensed Land Surface Phenology (LSP) parameter to conduct operational vegetation water balance modeling of rainfed systems at the LSP’s spatial scale using readily available global data sets. The result confirmed that the lowest seasonal /driest seasons/ water use estimated in 2002, which is 192mm and followed by 2003, 2009 and 2001cropping seasons with 205,230, and 231 mm respectively. On the contrary, moisture deficit free seasons’ were found during 2006–2008 and 2010 years with water use values ranges from 270-297 mm in depth. In the study area ETa and moisture availability (rainfall) have good positive linear relationship with coefficient of correlation (r=0.89). The result revealed that the highest yield reduction occurred during 2002 cropping season which is about 47% and then followed by 27%, 24%, 18%, and 18% in 2003, 2001, 2009 and 2005 cropping seasons respectively. The relationship between the water balance yield reduction estimation model and WRSI have good negative linear correlation determination coefficient (r=0.92). Finally, the VegET modeling approach was demonstrated to have a promising application for drought monitoring/crop performance/ and early warning applications at various spatial and time scales for rain-fed systems. Key words: LSP, Main Ethiopian Rift, Remote sensing, VegET model, WRSI, Yield reduction estimation