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Evaluating Potential Impacts of Climate Change on Surface
Water Resource Availability of Upper Awash Sub-basin,
Ethiopia rift valley basin.
By
Mekonnen Daba
Paper presented at African Dissemination Workshop on
Innovative Application of ICTs in Addressing Water - related
Impacts of Climate Change, 12th December, 2014 at Makerere
University, Kampala
Introduction
Climate changes
 In the surface
temperature,
 Changes in
precipitation
 evapotranspiration
rate
will accelerate the global
hydrological cycle(IPCC, 2007)
(IPCC, 2007) findings suggests that developing countries like Ethiopia
will be more vulnerable to climate change due to their economic,
climatic and geographic settings.
Climate changes alter regional hydrologic conditions and results in a
variety of impacts on water resource systems.
Such hydrologic changes will affect almost every aspect of human
well-being.
The economy of Ethiopia mainly depends on agriculture, and this in
turn largely depends on available water resources.
Key Sub-basin Problems
 Upper Awash sub-basin is normally endowed with land features
that are characterized by:
 Downstream irrigation , several towns, including the capital city,
Addis Ababa, and industrial enterprises in the study area has been
expanding from time to time there is an increasing demand for
water which leads to competition for water among different
sectors .
 Because of fast growing population rates, increasing resources and
industrial development, water is becoming a very scarce and
valuable resource.
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So What are the Innovations/Solutions?
Therefore assessing the impact of climate change on Surface water resource
availability,
Taking projections of climatic variables (e.g., precipitation and temperature at a
global scale,
 Downscaling these global-scale climatic variables to local-scale hydrologic
variables, and
Computing hydrological components for water resources variability and to give
a clue and increase awareness on the possible future risks of climate change in
order to mitigate the impacts climate change on water resources system.
The general objective of this study is to assess the impacts of climate change on
Surface water resource availability of upper Awash River basin by using the
Regional climate model and Soil and Water Assessment Tool (SWAT) hydrology
model.
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Study
Area map
Area
7240km
Found between
.
380’ to 390 5 00’ East 70 00’ and 100 30’ North
The• Awash
Basin has been traditionally divided into four distinct zones.
.
These are; Upper Basin, Upper Valley, Middle Valley and Lower Valley.
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The Methodology used
To evaluate climate change impacts on the water availability
of the following steps:
•Precipitation, and temperature, is extracted From GCM.
•A Dynamic downscale GCM output to RCM
•Bias corrected RCM with historical met data.
•Meteorological data + observed stream flows + (SWAT)
•Sensitivity analysis
calibrated and validated
•Simulation model at 2020s, 2050s and 2080s periods to assess the
climate scenarios and their impact on water resources system.
•Finally, To give a clue and increase awareness on the possible future
risks of climate change in order to mitigate the impacts climate
change on water resources system.
Key Finding's
Scenarios Developed for the Future time series (2011-2100)
• The general trend exhibits rising for temperature and decreasing
for total annual precipitation.
in Average
annual
minimum
Changes in rainfall and temperatureChanges
at upper
awash
basin
level
temperature
Changes in Average annual maximum
temperature
• 2020: +0.530C
• 2050: +1.180C
• 2080: +1.870C
• 2020: +0.580C
• 2050:+0.820C
• 2080:+2.140C
Also the estimate range is same with results of Girma.M (2012) and IPCC‟s average mean
annual temperature across Ethiopia will increase by between 0.9 and 1.1°C by the year 2030
and from 1.7 to 2.1°C by the year 2050.
Basin-average annual rainfall based on the ECHAM5 downscaling
2020: +2.4%
2050:-2.14%
2080:-10.109%
 by using the same model by (Girma.M 2012) point out that the CCLM
downscaling resulted in the upper Blue Nile were 1.8, -6.6 and -6.4% in
2011-2040, 2041-2070 and 2071-2100 respectively.
 The result of this analysis confirmed also with the IPCC‟s , precipitation
show a change of between 0.6 and 4.9% and 1.1 to 18.2% for 2030 and
2050, respectively (NM,A, 2006).
SWAT Hydrological Model Results
Flow Calibration
 Manual calibration (manually and automatically) using observed flow gauged at
the outlet of the watershed
 flow calibration at the outlet of Hombole and Melka kunture guaging stations
Hombole
RVE
Hombole
total flow(m3/s)
Period
gauged
simulated
gauged
simulated
R2
4640.26
3835.30
39.95
48.34
2692.96
3193.511
28.05
33.26
1993-2000
Average flow(m3/s)
Melka kunture
1993-2000
ENS
Bias
RMSE
0.83
0.80
8.38
16.78
0.90
0.91
9.6
13.4
Hombole
Melka kunture
0.320
0.186
Projected changes in the mean annual and seasonal stream flow
• Generally our results also suggest that the relationship of annual stream flow to
annual precipitation may change in a future climate in that a unit decrease in
precipitation will cause a larger decrease in stream flow for the year 2050 and
2080.
2020: +2.04%
2050:-9.90%
2080:-19.73%
2020: +4.9%
2050:-2.46%
2080:-18.14%
Monthly and annual impacts on future Surface
• The future scenario generatedrunoff
runoff shows a decreasing in the
future time series for the two periods from 2050 and 2080
comparing with the base period 1981-2010, but for the future
time series 2020 has an increasing in runoff comparing with the
base period.
2020: +8%
2050:-1.5%
2080:-3.52%
2020: +7.49%
2050:-0.99%
2080:+7.14%
Adaptation Strategies
Based on result of study stream flow and runoff decrease for
the future 2050 and 2080 periods, below are some possible
adaptation options to be implemented to overcome the
reduction stream flow and surface runoff in the watershed :Watershed based integrated water resource management
approach.
Constructing water storage structures to store excess water
flowing during rainy season so as to use it for dry season.
Consideration of climate change and its impact at all levels of
water resource development projects from the planning up to the
execution and management phases.
Conclusions
From the scenario results indicate that an increase in precipitation
resulted in an increase in annual runoff and stream flow.
In contrast, a temperature increase caused a decrease in annual runoff.
The runoff has a negative correlation with temperature change but a
positive correlation with precipitation change.
Generally the analyses carried out in this study revealed that climate
change would have a significant impact on the Surface runoff and stream
flow, and other hydrological parameter causing a possible reduction on the
total water availability in the upper awash sub-basin.
Change in precipitation and
Change in climate
aria les
Increase in temperature
Increase in evapotranspiration
impact on
tream flow
unoff
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Recommendations
In addition to fluctuations on temperature and precipitation, deforestation
and population growth due to industrial expansion in the area are among
current trends over the sub- basin.
Hence, it is important to examine the impacts of climate and land use
changes over the study area.
It is believed that the results of this study give a clue and increase awareness
on the possible future risks of climate change.
This in combination of the future climate change impact on reduction of the
available water in the watershed causes a water stress within and around the
Sub-basin.
Hence, it is strictly recommended that the adaptation measures proposed in
the above section need to be effectively implemented in any existing and
This work was supported by International Development Research
Center (IDRC) through ICTWCC Kenya project funded.
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