IMPACT OF LAND USE DYNAMICS ON RESERVIOR

IMPACT OF LAND USE DYNAMICS ON RESERVIOR SEDIMENTATIONIN MEGECH WATERSHED, UPPER BLUE NILE, ETHIOPIAByIBRAHIM TEMAM JUHARA Thesis Submitted ToThe Department of Civil Engineering for the Partial Fulfilment of the Requirements for theDegree of Master of Science in Civil Engineering (Hydraulic Engineering)ADDIS ABABA SCIENCE AND TECHNOLOGY UNIVERSITYJUNE 2018

DECLARATIONI hereby declare that this thesis entitled “Impact of Land Use Dynamics on ReservoirSedimentation in Megech Watershed” was composed by myself, with the guidance of myadvisor, that the work contained herein is my own except where explicitly stated otherwise inthe text, and that this work has not been submitted, in whole or in part, for any other degree orprofessional qualification.Name:Signature, Date:Ibrahim Temami

CERTIFICATIONThis is to certify that the thesis prepared by Mr. Ibrahim Temam Juhar entitled “Impact ofLand Use Dynamics on Reservoir Sedimentation in Megech Watershed” and submitted infulfillment of requirements for the Degree of Master of Science complies with the regulationof the University and meets the accepted standards with respect to originality and quality.Date of Defense: June 8, 2018Principal Advisor1.SignatureDateMembers of the Examining board:1.External Examiner2.Internal Examiner3.ERA PG, Programme Coordinator4.Head, Civil Eng’g Department5.Dean, College of eSignatureDateSignatureand Civil EngineeringiiDate

ACKNOWLEDGEMENTSI would like to express my deepest gratitude to my thesis advisor, Dr. Fitsum Tesfayefor his advice ,comment, valuable suggestions, encouragement and guidance of my thesis workI would like to extend my special thanks to Ministry of Water Resource Energy and Irrigation,Ethiopian Construction Work Design and Supervision Corporation, National MetrologyAgency, since they were provided the necessary data for my thesis work.Finally, I would like to thank Ethiopian Road Authority and Addis Ababa Science andTechnology for the free scholarship.iii

ABSTRACTReservoir sedimentation is a gradual accumulation of the incoming sediment load from ariver. The potential effects of land use/cover change resulting soil erosion and producing oversediment on surface water source of reservoirs, which are losing their capacity due tosedimentation processes, and are therefore seriously threat on their performance. Thereforethe main intention of this study is to evaluate the impact of land use dynamics on reservoirsedimentation in Megech watershed. ArcGIS and ERDAS usedto generate three landuse/cover maps from Landsat TM, ETM and ETM acquired in 1986 ,2006 and 2015respectively, The land use maps were generated using the Maximum Likelihood Algorithm ofSupervised Classification. The accuracy of the classified maps was assessed using errormatrix and kappa statistic. The result of this analysis showed that the cultivated land and builtup have expanded during the study period of 1986-2015. Using the three generated land usemaps, SWAT model, the same climate data and other input for the period of 1986 to 2015 threeindependent model were prepared, calibrate and validate with respected period. Then to showthe impact of land use dynamics on sediment load the three independent models were runssimulations for the same period from 2003 to 2015. The performance of the SWAT model wasevaluated through sensitivity analysis, calibration, and validation using SWAT-CUP softwareSUFI 2 program. Both the calibration and validation results showed good match betweenmeasured and simulated stream flow and sediment load data with acceptable range, coefficientof determination (R2)(0.68 to 0.88 for Calibration and 0.62 to 0.86 for Validation ) and NashSutcliffe efficiency (ENS)(0.64 to 0.88 for Calibration and 0.61 to 0.85 for Validation).Theresult of this study showed the annual simulated sediment yield 353,835 tons/year (716.26tons/km2/year) using land use 1986, 482,319 tons/year (976.36 tons/km2/year) using land use2006 and 557,184 tons/year (1127.90 tons/km2/year) using land use 2015. According to theEmpirical Area Reduction method, the Megech reservoir will have useful life of 125, 90 and78 year using land use 1986, 2006 and 2015 respectively, with trap efficiency 98% and averagedeposit density 1.12 t/m3. Generally, the analysis indicated that increasing in sediment loadand decrease in useful life of reservoir due to the land cover changes during the studyperiod.Key words: Megech watershed, Land use dynamics, Stream flow, Sediment yield, ReservoirSedimentation, GIS, ERDAS, SWAT model, SWAT-CUP, SUFI 2iv

Table of ContentsDECLARATION. iCERTIFICATION .iiACKNOWLEDGEMENTS . iiiABSTRACT . ivLIST OF TABLE . viiiLIST OF FIGURE . ixLIST OF ABBREVATION . xiCHAPTER ONE . 11.INTRODUCTION. 11.1Background . 11.2Problem of statement . 31.3Objective of the study . 41.3.1General objective . 41.3.2Specific objectives . 41.4Research questions . 41.5Significance of the study . 5CHAPTER TWO . 62LITERATURE REVIEW . 62.1Concept and definition of land use and land cover change . 62.2Soil erosion and sedimentation . 62.3Impact of land use on erosion and sediment load . 72.4Remote sense and GIS for land cover classification . 82.5Hydrological model . 92.6Hydrological model selection criteria . 122.7Reasons for selecting SWAT model . 132.8Previous studies in Ethiopia . 13CHAPTER THREE . 163MATERIALS AND METHODS . 163.1Description of the study area . 163.1.1Location . 163.1.2Climate . 183.1.3Topography . 183.1.4Land cover . 193.1.5General work flow of the study . 203.2Data collection and analysis . 213.2.1Hydro-meteorological data screening . 21v

3.2.2Filling the missed rainfall data . 223.2.3Test for consistency of the record . 263.3Image processing . 273.3.1Land use/cover image classification . 283.3.2Accuracy assessment . 293.3.3Flow chart for landuse classification . 313.4Model input . 323.4.1Digital elevation model . 323.4.2Weather data . 333.4.3Soil data . 333.4.4Land use/cover . 353.4.5Hydrological data . 353.5Model setup . 363.5.1Watershed delineation . 363.5.2Hydrologic response units analysis . 383.5.3Weather station . 393.6Description of SWAT model . 403.6.1Surface runoff . 413.6.2Potential evapotranspiration . 433.6.3Ground water flow . 433.6.4Flow routing phase . 443.6.5SWAT sediment simulation . 443.6.6Sensitivity, Calibration and Validation analysis . 453.7Evaluation of land use dynamics on reservoir sedimentation . 503.8Sedimentation rate . 503.8.1Empirical area reduction method . 50CHAPTER FOUR . 514RESULT AND DISCUSSION . 514.1Land cover classification . 514.1.1Accuracy assessment. 514.1.2Land use/cover classes . 524.1.3Trends in land use/cover classes (1986-2015) . 554.2Sensitive parameters . 574.2.1Parameters sensitive to flow . 584.2.2Parameters sensitive to sediment . 614.3Model calibration and validation . 634.3.1Model calibration for flow . 63vi

4.3.2Model validation for flow . 654.3.3Model calibration for sediment . 684.3.4Model validation for sediment . 704.4Impact of land use dynamics on sediment yield . 724.5Comparison with sediment yield estimates from other reservoirs . 744.6Sedimentation rate of Megech reservior . 744.6.1Trap efficiency . 744.6.2Specific weight of sediment deposit . 764.6.3Sediment distribution in Megech reservoir . 774.7Reducing sediment inflow to reservoir . 80CHAPETER FIVE . 815CONCLUSION AND RECOMMENDATION . 815.1Conclusion. 815.2Recommendation . 846REFERENCE . 857APPENDIX . 91vii

LIST OF TABLETable 3.1: Thissen weight for selected stations in Megech watershed stations . 26Table 3.2: The Acquisition dates, path/row, resolution of the images . 28Table 3.3: Land use/cover description for Megech watershed (based on field observation) . 28Table 3.4: Meterological station names, location and variables . 33Table 3.5: Soil types of Megech watershed with their symbols and areal coverage . 35Table 3.6: Soil types of Megech watershed with their symbols and areal coverage . 35Table 4.1: Base error matrix of 2015 land use/cover map . 51Table 4.2: Accuracy assessment of 2015 land use/cover class . 51Table 4.3: Area of land use/cover types and change statistics of Megech watershed . 56Table 4.4: Parameter rank based on p-value and t-value for Land use 2015 model . 58Table 4.5: Parameter rank based on p-value and t-value for Land use 2006 model . 59Table 4.6: Parameter rank based on p-value and t-value for Land use 1986 model . 60Table 4.7: Parameters highly sensitive to sediment for Land use 2015 model. 62Table 4.8: Parameters highly sensitive to sediment for Land use 2006 model. 62Table 4.9: Parameters highly sensitive to sediment for Land use 1986 model. 63Table 4.10: Summary of stat txt for flow calibration period for land use 2015 model . 64Table 4.11: Summery of stat txt for flow calibration period for land use 2006 model . 64Table 4.12: Summery stat txt for flow calibration period for land use 1986 model . 65Table 4.13: Summery stat txt for flow validation period for land use 2015 model . 66Table 4.14: Summery stat txt for flow validation period for land use 2006 model . 66Table 4.15: Summery stat txt for flow validation period for land use 1986 model . 67Table 4.16: Summery stat txt for sediment calibration period for land use 2015 model . 68Table 4.17: Summery stat txt for sediment calibration period for land use 2006 model . 69Table 4.18: Summery of stat txt for sediment calibration period for land use 1986 model . 70Table 4.19: Summery of stat txt for sediment validation period for land use 2015 model . 71Table 4.20: Summery of stat txt for sediment validation for land use 2006 model . 71Table 4.21: Summary of stat txt for sediment validation period for land use 1986 model . 72Table 4.22: Average annual sediment yield for the period 2003 to 2015 . 73Table 4.23 : Sediment yield estimate for hydropower reserviors in Ethiopia . 74Table 4.24: Cofficent B and intial weight values for consolidation calculation . 76viii

LIST OF FIGUREFigure 3.1: Location of Megech watershed . 17Figure 3.2: Elevation map of Megech watershed . 19Figure 3.3: Land use/cover map of Megech watershed . 19Figure 3.4: General flow chart used for this study. 20Figure 3.5: Location of meteological station in and around the stations . 22Figure 3.6: Mean monthly rainfall distribution of selected meterological stations for theperiod from 1986 to 2015. . 25Figure 3.7: Discharge record of Megech River at Azezo station (1990-2014) . 25Figure 3.8: Duble mass curve for selected stations. 26Figure 3.9: Thiessen polygo for Megech watershed . 27Figure 3.10: Flow chart for land use classification used for this study . 31Figure 3.11: Digital elevation model of Megech watershed . 32Figure 3.12: Map of the soil types of Megech watershed . 34Figure 3.13: Sediment rating curve . 36Figure 3.14: Sub watershed map of Megech watershed .

sedimentation processes, and are therefore seriously threat on their performance. Therefore the main intention of this study is to evaluate the impact of land use dynamics on reservoir sedimentation in Megech waters