Agricultural Water Management Modeling and Analysis Under Climate Change and Land Transformation (A Case Study of Lower Omo Ghibe Basin)
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Date
2018-05
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Addis Ababa University
Abstract
Human activities and climate factors both affect the availability of water resources and the
sustainability of water management and that in turn affect agricultural water management
especially in already dry regions, water has become scarcer with increasing requirements from
growing population, economic development. Although progress has been made in
understanding variability of runoff, the impacts of climate variability and human activities on
agricultural water management (actual evapotranspiration) and (discharge accumulated in the
river network) remain less well understood.
South omo Gibe basin which is one of the sub basin in Ethiopia has suitable land water resource
for agriculture for both farm and livestock and currently huge investment are found on irrigation
project, and from these the dominant is state owned irrigation like kuraz sugar development
irrigation project in the sub basin which planned to irrigate sugarcane on 175,000 hectare of
land. According to works design and supervision enterprise that prepare design document of the
project the water requirement of the plant is modeled with cropwat considering only
atmospheric water demand and put the yield in figure in its report.
However now a time In south Omo Gibe sun basin a frequent happening of high and low
rainfall, less work on soil conservation practice and deforestation are observed as causes of
changing of climate and land degradation that make the need for improved and resilient
agricultural water management to have greater yield of the crop with environmental
sustainability and so efforts towards improved and resilient agricultural water management is
must.
Therefore, the main objective of the research presented here is to study the effect of climate
change specifically drought and land degradation on water demand and crop yield in the area of
study and compare the existing crop oriented model used for the design of crop water
requirement of the crop in the project area with agro hydrological model for better irrigation
management under climate change and land transformation. To achieve this purpose, an
available code that takes into account the interaction between soil, water, atmosphere and plants
SWAP model is used after assessing the challenges in the sub basin and identifying adaptation
strategy for improved agricultural water management and compared with Cropwat model.
consequently, it is tried to analyze the impact of future climate changes and land transformation
water demand for irrigation and relative crop yield in the Kuraz irrigation project area.
From the result of the performance of the two model SWAP model result of actual
evapotranspiration and irrigation water requirement is greater than the designed crop water
requirement of cropwat model output which can be calibrated with yield of sugarcane. And the
comparison of the two models shows that SWAP model outputindicate the actual
evapotranpiration and irrigation water requirement is greater than the CROPWAT model output f the designed irrigation water requirement that can make conform with yield reduction of
sugarcane the in project area as a calibration method due to shortage of data.
Even though the reduction of sugarcane is happen due to technical inefficiency as I can get the
result of research paper on irrigation management practices in kuraz irrigation project, climate
change and land degradation plays large effect in this technical inefficiency of irrigation water
management more than different tillage practices. in this research due to shortage of data to
measure soil moisture and ground water data in the project area I used the yield reduction data
from analysis of technical efficiency sugarcane production.
From this result neglecting other factors that decrease the yield of sugarcane and considering the
effect of climate change and land degradation only, it shows the need of irrigation water will be
high to maintain good yield of sugarcane in the future. Today, the sugar corporation supplies
300 m
3
/sec which is the minimum release discharge from Gibe III hydropower project. This
means that the corporation should focus on works that increase the amount of water for
irrigation in the future.
Consequently, taking into account all the simplification and the uncertainties in the model, it is
safer for the corporation to increase the water supply capability in the future, particularly using
a better approach of soil and water management integrated with sub basin scale soil and water
conservation practices should be followed, in order to cope the increasing water demand in the
future.
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Keywords
Water Management, Climate Change, Lower Omo Ghibe Basin, Land Transformation