Irrigation Engineeringhttp://ir.haramaya.edu.et//hru/handle/123456789/732024-03-29T02:28:54Z2024-03-29T02:28:54ZPERFORMANCE ANALYSIS OF SMALL SCALE IRRIGATION SCHEME OF RAMIS RIVER, IN THE CASE OF DIVERSION HEAD WORK, EAST HARARGHE, ETHIOPIAMOHAMMED USMAILMeseret Dawit (PhD)http://ir.haramaya.edu.et//hru/handle/123456789/74732024-03-06T08:39:44Z2023-12-01T00:00:00ZPERFORMANCE ANALYSIS OF SMALL SCALE IRRIGATION SCHEME OF RAMIS RIVER, IN THE CASE OF DIVERSION HEAD WORK, EAST HARARGHE, ETHIOPIA
MOHAMMED USMAIL; Meseret Dawit (PhD)
Many irrigation schemes have been designed and built in Ethiopia recently; about 90% of small-scale irrigation projects are underperforming. This study aimed to assess the performance analysis of three selected diversion weirs through performance indicators of hydrological, hydraulic and structural analysis. Secondary and primary data are collected and analyzed for the determination of peak flood design discharge and design of diversion weir. For peak, flood runoff estimation using 23-year rainfall from Chelenko, Kullubi and Bedeno metrological stations analyzed for the future 50 years, return period rainfall was 136mm for Lega Kosta and Chafe Ramis, whereas for Gololcha Ramis 117mm were used. SCS unit hydrograph Methods were used for peak flood analysis based on Land use/cover and sub watershed analysis done by GIS 10.4.2. The design discharge performance evaluation for the diversion weir corresponding to a return period of 1 in 50 years Lega Kosta, Chafe Ramis and Gololcha Ramis peak design flood are 203m3/sec, 289m3/sec and 352m3/sec respectively, whereas from the designed document represent 189m3/sec, 191.44m3/sec and 231.4m3/sec. The results indicate that total discharges passes over of existing diversion weir structures, 100.83m3/sec, 131.58m3/sec, and 256.25m3/sec are less than peak discharges, which implies the structures flood passage capacities are 50%, 54.4%, and 27.3% of the actual design discharges below the standard discharges passes and flood passage capacity of the existing under-sluice sections were 5.64%, 8.9%, and 9.12%, also below recommended for Lega Kosta, Chafe Ramis, and Gololcha Ramis diversion headwork structures respectively. The hydraulic performance analysis's main problems observed in the Lega Kosta, Chafe Ramis and Gololcha Ramis scheme were sedimentation of headwork, damage of intakes and sluice gates, clogging of intakes, and damages to distribution systems and weir bodies. This result shows that the cause’s failures were due to wrong design discharge estimation. The structural stability analyzed indicates stability analysis of the weir body and its appurtenance structures was analyzed and compared with standard safety factor. Finally, the major causes of the diversion headwork 48.7%, 28% and 23.3% in hydrological, hydraulic and structures underperform recently, which will hinder their performance in the future too. Therefore, the proper hydrologic, hydraulic and structural design of the diversion headwork structures is a very important task that contributes to the good performance and sustainability of the structures.
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2023-12-01T00:00:00ZINVESTIGATION OF THE CAUSES FOR MALFUNCTION OF MECHAWA SMALL SCALE IRRIGATION SCHEMES, OROMIA, ETHIOPIAKedir Kaso Harka(Ph.D.) Meseret Dawithttp://ir.haramaya.edu.et//hru/handle/123456789/70252023-12-04T08:09:18Z2023-10-01T00:00:00ZINVESTIGATION OF THE CAUSES FOR MALFUNCTION OF MECHAWA SMALL SCALE IRRIGATION SCHEMES, OROMIA, ETHIOPIA
Kedir Kaso Harka; (Ph.D.) Meseret Dawit
Ethiopia faces a number of challenges in the development and management of irrigation
schemes, including biophysical, technical, socioeconomic, and institutional factors. Many
developed irrigation Schemes have been failed due to design fault, lack of adequate data,
inadequate participation of stakeholders, and watershed degradation. The study was carried
out to assess and identify the causes of the Mechawa diversion weir failure which is one of the
Chiro district irrigation schemes. Thus, the encountered causes can be used for a variety of
purposes, including the construction of a new diversion structure (either as a replacement for
existing structures or as an entirely new structure), and existing structure rehabilitation. In this
study, Hydraulic and hydrologic failures of scheme were assessed using collected primary and
secondary data. The collected data were analyzed using ArcGIS, Micro soft excel, and SPSS
software. The failure of the scheme due to hydrologic data was evaluated using the SCS CN
method. The hydrological analysis has been conducted based on 21 years of maximum daily
rainfall data. The frequency analysis has been carried out by different methods and the Gumble
EVI method is adopted to estimate daily point rainfall. The peak discharge computed by
(USSCS) method using estimated point rainfall is 204 m
3
/sec for the scheme. Since the peak
discharge mentioned in the design document which means 190m3
/sec was underestimated, the
peak discharge calculated by the SCS curve number method is adopted. According to the results
obtained using SPSS software, 46% respondents confirm that there was poor study and design,
and 24% poor selection of competent contractors and supervision gap, 64% poor community
participation during planning and implementation. On other hand, an attempt was made to
understand the design problems concerning hydrologic, hydraulic, and structural design
aspects using secondary data. The problem of inefficiency in irrigation schemes can be
emanated from technical and nontechnical factors like poor community participation, poor
scheme management, and absence of operation and maintenance. Therefore, it is essential to
accord due consideration to these issues to properly address the problems and to design the
correct operational strategy. Finally, the restudy and redesign should be done from minor
repair to full re-engineering Measures are recommended
104p.
2023-10-01T00:00:00ZINVESTIGATION OF WATER RESOURCE AVAILABILITY AND IRRIGATION WATER DEMAND UNDER CLIMATE CHANGE IN DAWA RIVER BASIN, ETHIOPIAHalake Tadi Jirmo(Prof.) Mekonen Ayanahttp://ir.haramaya.edu.et//hru/handle/123456789/70202023-12-04T07:10:37Z2023-08-01T00:00:00ZINVESTIGATION OF WATER RESOURCE AVAILABILITY AND IRRIGATION WATER DEMAND UNDER CLIMATE CHANGE IN DAWA RIVER BASIN, ETHIOPIA
Halake Tadi Jirmo; (Prof.) Mekonen Ayana
Climate change and its impact is the concerned issue that threatening the world wide especially
east Africa including Ethiopia. Water resource availability is directly impacted by climate change,
which is the outcome of change in climate variables like rainfall and temperature. Accordingly
this study aimed to examine the response of water resource availability and irrigation water
demand(IWD) to climate change in Dawa sub basin, Ethiopia, using ensemble of regional climate
model (RCM) output from coordinated regional climate downscaling experiment (CORDEX)
Africa under future medium and high climate change scenarios(RCP4.5 and RCP8.5).The bias
corrected result showed that, the spatially averaged annual rainfall was projected to decline by -
17.95% and -19.66% under RCP 4.5 and RCP8.5 scenarios, respectively for the 2021-2050 time
period. In the same way, the RCP4.5 and RCP8.5 scenarios, projected that the annual rainfall
would decline by -12.9% and-22.4% respectively, in the time period 2051-2080. Mean annual
maximum temperature was projected to increase by 1.6℃ and 2.3℃ under RCP4.5 and RCP8.5
of 2021-2050 and by 1.4℃ and 2.8℃ under RCP4.5 and RCP8.5 scenarios of 2051-2080 time
interval. Accordingly the mean annual minimum temperature was projected to increase by1.6℃
and 3.5℃ under RCP4.5 and RCP8.5 scenarios of 2021-2050 and by 2.03℃ and 4.1℃ in 2051-
2080 under RCP4.5 and RCP8.5 scenarios respectively. To analysis water resource availability
and irrigation water demand soil and water assessment tool (SWAT) and CROPWAT model were
employed. SWAT was calibrated and validated on monthly base streamflow and performed well
with statistical model performance measures of NSE=0.75 and R2=0.82 for calibration and
NSE=0.71 and R2=0.77 for validation. In comparison to the baseline period, it is expected that
the future annual streamflow will decline under RCP4.5 scenario by -31.3% to -52.9% and under
RCP8.5 scenarios by -27.5 to -41.3%. CROPWAT estimate current and future irrigation water
demand and results indicated that the averaged IWD would increase by 5.8% and 3% under
RCP4.5 and by 12% and 9.2% under RCP8.5 scenarios. To sum up, this study looked into how the
projected change in rainfall and temperature resulted in reduction of water resources availability
and increment of irrigation water demand of maize in Dawa river basin. Thus sustainable and
effective adaptive measures is crucial for future water resource management
136p.
2023-08-01T00:00:00ZIMPACTS OF CLIMATE CHANGE ON HYDRO-METEOROLOGICAL DROUGHT ON DAWA WATERSHED, GENALE DAWA RIVER BASIN, ETHIOPIAAyana Bulti OlanaFantaw Abegaz (Ph.D.)http://ir.haramaya.edu.et//hru/handle/123456789/69942023-11-24T07:05:14Z2023-11-01T00:00:00ZIMPACTS OF CLIMATE CHANGE ON HYDRO-METEOROLOGICAL DROUGHT ON DAWA WATERSHED, GENALE DAWA RIVER BASIN, ETHIOPIA
Ayana Bulti Olana; Fantaw Abegaz (Ph.D.)
Climate change is statistical variations over an extended period in the features of the climate system, such as variations in global temperatures and precipitation, caused by human and natural sources. Major occurrence that has an impact on the agricultural, social, economic, and environmental spheres was drought. Understanding climate change affects frequency, length, and severity of hydro meteorological droughts is an issues. In this work coordinated regional climate downscaling experiment for Africa, which integrates climate forecasts from Coupled Model Intercomparison Project5 based on an ensemble of GCM-RCM, were used to statistically downscaled the climate change scenarios.The aim of this study was to estimate climate change impacts on Hydro-meteorological drought for early warning response and development of climate adaptation and mitigation options. The impact of climate changes during a period from 2021-2080 has evaluated by reporting under RCP4.5 and 8.5 scenarios. For the extraction and bias correction of the daily maximum and minimum temperature, as well as precipitation of 30- year overlap periods, CMhyd has employed. DrinC tool was used to characterize the meteorological and hydrological drought. The annually minimum temperatures are predicted to increase by 2.94, 3.45, 3.21, and 3.59°c and annually maximum temperatures increased by 2.61, 2.83, 2.71 and 3.36°c for RCP4.5 and RCP8.5 respectively. Regarding the change in rainfall reveals annual average decreases of 8.45- 9.3% and 10.5-10.95% at RCP4.5 and RCP8.5, respectively. Considering the evaluated parameters, minimum and maximum temperatures increased trends but for the rainfall, large fluctuations predicted. Moreover, in the study years for the parameters in all simulated models, RCP 8.5 scenario estimated a higher amount than RCP 4.5 scenario.HBV models successfully calibrated from 1991-2010 and verified from 2011-2020. Overall, the models monthly time scale calibration R2=0.88 and NSE=0.77 and validation R2=0.86 and NSE=0.83 with the HBV Light model performed well under both scenarios of RCP4.5 and 8.5 for two projected periods. The simulation findings from the HBV indicated that the mean yearly discharge drastically declined in comparison to the baseline periods for both scenarios.Generally, HBV indicates a percentage decrease in the total average annual flow volume of 1.6% to 3.5% and 4.6% to 4.9%. The only increment in Belg season ranges between 39.3% and 40% in 2020s and 39.2% to 38.5% in 2050s. Decreases in mean total annual, seasonal and monthly flow volume seen for times when there is a corresponding decline in mean annual, seasonal, and monthly precipitation. To offset this variation community should adopt various soil and water conservation strategies, using drought tolerant crop in the watershed, implement various trees, appropriately design and apply a water harvesting structure and Surface runoff harvesting to the watershed. As a result, feature research should consider wet number and wet days for drought impacts and more multiple GCM-RCM driving models was used to improve more prediction accuracy in the future climate and drought change.
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