Abstract:
Most hydrological and water resource simulation models require relatively accurate
estimation of spatially distributed rainfall and evapotranspiration data sets. This
research has been conducted with the objective of producing these vital elements of
the water balance that can be used as an input to the water resources assessment
tools and agricultural water management.
Spatially distributed rainfall has been acquired from remotely sensed FEWS data
set. Ground validation has been conducted by comparing gridded gauged rainfall data
with the remotely sensed FEWS data set. As a result the annual remotely sensed
FEWS data set has been found to underestimate the measured ground based data.
The annual spatial mean rainfall was underestimated by 33.2% and 35% for 2007 and
2008 respectively. Therefore these biases of the satellite data were adjusted and a
spatially distributed rainfall of 1 km grid was obtained.
The daily , monthly and yearly evapotranspiration over the Tana sub basin has
been computed by Surface Energy Balance System (SEES) algorithm using MODIS
land surface products and some ancillary meteorological data with a one km resolution
for the entire Lake Tana sub-basin.
Open water evaporation of the lake has been estimated with a one km resolution
from a remotely sensed data and the spatial averages are 1631.67 and 1623.42 mm
for 2007 and 2008 respectively.
The change in storage estimated from the Topex/Poseidion Jason-2 lake level
variation shows that the lake has increased 290 mm and reduced 301 mm in 2007 and
2008 from the annual average levels of 2006 and 2007 respectivel
