Title: Modelling of Cascade Dams & Reservoir Operation for Optimal Water Use: Application to the Omo River Basin, E

1. Title: Modelling of Cascade Dams & Reservoir Operation for Optimal Water Use: Application to the Omo River Basin, Ethiopia Supervisor Prof. Dr. rer. nat Manfred Koch (Uni-Kassel) Dr. Yilma Sileshi (AAU, Ethiopia) November 09, 2012 Kassel, Germany

2. Outline • Background • Study Area • Objectives 4. SDSM application 5. SWAT Model 6. HEC-ResSim Model 7. References Modeling of Cascade Dams & Reservoir Operation

3. 1. Background • Over 45 000 times in the last century, people took the decision to build a dam. • Dams were built to provide water for irrigated agriculture, domestic or industrial use, to generate hydropower or help control floods (WCD, 2000). • Hydroelectric power dams currently provide 19% of the world’s electricity supply. • Worldwide, water demands have roughly tripled since 1950, & dams have helped satisfy that demand. • Contribute directly to 12–16% of the global food production (WCD, 2000). Modeling of Cascade Dams & Reservoir Operation

4. Background cont... • In relation to constructed dams, Africa contains some of the world’s largest dams (e.g., Owen Falls (Uganda), Kariba (Zimbabwe) & Aswan High (Egypt). (ICOLD, 2003). • Furthermore, Ethiopia has 13 hydropower dams and out of these ten were completed & three are under construction. • According to 2005 plan of EEPCo, when the 3 dams complete, the capacity of the hydropower will increase to the capacity of 3,125 MW which will satisfy the electricity demand of the country. Modeling of Cascade Dams & Reservoir Operation

5. Background cont... • On the contrary, dams have considerable influence on d/s river ecosystems, in many cases extending for hundreds of kilometers below a dam. • One of the problem encountered for the Ethiopian Gov’t has been opposition from International River (IR)-People-Water-Life in the construction of Gibe dam III in Omo river which will expect catastrophic effect on the d/s users & ecosystem. Modeling of Cascade Dams & Reservoir Operation

6. Background cont... • To take account of this problem the WCD called for a more equitable distribution of the benefits to be gained from large dams & proposed the inclusion of all identified stakeholders in the planning & management of water resources stored in a reservoir (WCD, 2000). • To achieve this, dams & reservoirs operation must take into account the availability of the water resource in the basin, water uses u/s & d/s of the dam & must give consideration to political, organizational, social & environmental factors, as well as economic factor (McCartney & Acreman, 2001). Modeling of Cascade Dams & Reservoir Operation

7. Background cont... • Hence, • New strategies for effective use of the water in the basin particularly in the Omo River basin will be needed for water development & management to avert water scarcities that could depress d/s users & damage the environment. • A large share of water to meet new demands must come from water saved from existing uses through a comprehensive reform of water policy. • Integrated management must be the primary approach to addressing sustainable water resources, both for subsystem & river basin level. Modeling of Cascade Dams & Reservoir Operation

8. 2. Study Area • The Omo-Gibe River Basin is almost 79,000 km2 in area • The basin lies longitude 4°30'N - 9°30'N & latitude 35°0'E - 38°0'E, altitude of 2800masl. • The general direction of flow of the river is southwards towards the Omo River/Lake Turkana Trough, a fault feature. Modeling of Cascade Dams & Reservoir Operation

9. 3. Objective of Research • Main objective • The purpose of this study is to model cascade dams & reservoirs operation in the Omo river basin to satisfactorily simulate the operation of dams & reservoirs for optimal water use. Modeling of Cascade Dams & Reservoir Operation

10. Specific objectives The specific objectives of the proposed study are • To simulate runoff & inflow to the reservoirs in the Omo river basin using the SWAT model. • To develop & recommend optimal dam & reservoir operation rule curves for cascade dams & reservoirs, more soundly based on evaluating the feasibility of various reservoir operating alternatives. • To evaluate the effects of various reservoir operating alternatives on either preventing flooding or avoiding precarious low flow at locations d/s of the reservoirs. Modeling of Cascade Dams & Reservoir Operation

11. Hydrological & Hydraulic Situation in the Omo River Basin Modeling of Cascade Dams & Reservoir Operation

12. GIBE-I Modeling of Cascade Dams & Reservoir Operation

13. GIBE-II Modeling of Cascade Dams & Reservoir Operation

14. GIBE-III Modeling of Cascade Dams & Reservoir Operation

15. GIBE-IV Modeling of Cascade Dams & Reservoir Operation

16. GIBE-V Modeling of Cascade Dams & Reservoir Operation

17. . Lake Turkana Modeling of Cascade Dams & Reservoir Operation

18. 4. The Statistical DownScaling Model: application to filling and forcasting Metrological data 4.1 Introduction • The Statistical DownScaling Model (SDSM) is a freely available tool that produces high resolution climate change scenarios. • Downscaling is a technique by which properties of the free atmosphere are used to predict local meteorological conditions. • The large-scale information may originate from systematic weather observations or from climate model outputs. Modeling of Cascade Dams & Reservoir Operation

19. SDSM cont.... • This freely available software enables the production of climate change time series at sites for which there are sufficient daily data for model calibration, as well as archived General Circulation Model (GCM) output to generate scenarios. • SDSM can also be used as a stochastic weather generator or to infill gaps in meteorological data. Modeling of Cascade Dams & Reservoir Operation

20. Objective • To filling and forecasting Rainfall and Temperature data for Omo Metrological Stations Modeling of Cascade Dams & Reservoir Operation

21. Methdology • The structure and operation of SDSM has seven tasks to infill and generate data. These are: • Quality control and data transformation; • Screening of potential downscaling predictor variables; • Model calibration; • Generation of ensembles of current weather data using observed predictor variables; • Statistical analysis of observed data and climate change scenarios; • Graphing model output; • Generation of ensembles of future weather data. Modeling of Cascade Dams & Reservoir Operation

22. RESULT Modeling of Cascade Dams & Reservoir Operation

23. Asendabo Station-Precipitation Unfilled & filled data chart Modeling of Cascade Dams & Reservoir Operation

24. Statistical Analysis using Mean, Variance,Sum & pdf plot of unfilled & Filled Precipition data Modeling of Cascade Dams & Reservoir Operation

25. Generated Precipitation data from 2001-2040 .

26. Statistical Analysis using Mean, Varience, Sum & pdf of Observed & Modelled data . . Modeling of Cascade Dams & Reservoir Operation

27. Asendabo Unfilled and Filled Maximum Temperature data chart .

28. Statistical Analysis of using Mean, Variance,Sum & pdf plot of Max Unfilled & Filled Temp data Modeling of Cascade Dams & Reservoir Operation

29. Generated Maximum Temperature from 2001-2040 .

30. Statistical Analysis using Mean, Varience, Sum & pdf of Generated data . . Modeling of Cascade Dams & Reservoir Operation

31. Asendabo Unfilled and Filled Minimum Temperature data from 1970-2000 .

32. Statistical Analysis using Mean, Variance,Sum & pdf plot of Min. Temp Modeling of Cascade Dams & Reservoir Operation

33. Generated Minimum Temperature from 2001-2040 .

34. Statistical Analysis using Mean, Varience, Sum & pdf of Generated data . . Modeling of Cascade Dams & Reservoir Operation

35. Summary By the same procedure 18 Precipitation station were filled and generated 13 Maximum and Minimum temperature station data were filled and generated

36. 5. Hydrological Model SWAT 5.1. Introduction • SWAT is a hydrological model that attempt to describe the physical processes controlling the transformation of precipitation to runoff. • The major hydrologic processes described by this model include: Canopy interception, Evaporation, Transpiration, Snowmelt, Interflow, Overland flow, Channel flow, unsaturated subsurface flow and saturated subsurface flow. Modeling of Cascade Dams & Reservoir Operation

37. Introduction cont... • SWAT was used to assess and predict the impact of land management practices on water in Omo river basin with varying soils, land use and management conditions over long periods of time. Modeling of Cascade Dams & Reservoir Operation

38. 5.2. Objective • To simulate runoff & inflow to the reservoirs in the Omo river basin. Modeling of Cascade Dams & Reservoir Operation

39. 5.3. Methodology • Input files needed for daily stream flow computation were : • the digital elevation model (DEM), • land cover, • soil layers, • daily values of precipitation, max.& min. air temp, solar radiation, RH, & WS, • Hydrological flow data. Modeling of Cascade Dams & Reservoir Operation

40. Methodology cont... • Missing metrological data were filled • using WXGEN weather generator model of SWAT, • SDSM, and • Hydrological flow data were filled by Multiple regression of R program • The Digital Elevation Model (DEM) was used to create stream network, subbasin & delineate the watershed boundary & also calculate the sub basin parameters. • Threshold value of 2%, 5% & 5% were taken for land use, soil & slope in order to keep the number of HRUs to a reasonable number for modeling the water assessment of the basin. Modeling of Cascade Dams & Reservoir Operation

41. Methodology cont... • Runoff was predicted separately for each HRU & routed to obtain the total runoff for the watershed, and • Calibration, Validation & Uncertainity of the model using SWAT_CUP 4.3.7. Modeling of Cascade Dams & Reservoir Operation

42. 5.4. Results 1. Model Calibration and Validation of Abelti Sub watershed • Abelti sub-watershed has an area of 15,495 km² and 30% of the total watershed delineated at Omorate. Modeling of Cascade Dams & Reservoir Operation

43. Model Calibration and Validation of Abelti Sub watershed • Using SWAT model the area was delineated into 9 sub watersheds, which were further, divided into 122 HRUs. • Simulated flow at the outlet was compared with the observed flow. Modeling of Cascade Dams & Reservoir Operation

44. Flow Calibration At Abelti Modeling of Cascade Dams & Reservoir Operation

45. Sensitivity Analysis Modeling of Cascade Dams & Reservoir Operation

46. 2. Model Calibration and Validation of Karodus Sub watershed • Karo Duse sub-watershed covers 64,518 km² and 95.6% of the total watershed delineated at the Omorate. • Land use and land cover was reclassified into 7 broad categories Modeling of Cascade Dams & Reservoir Operation

47. Model Calibration and Validation of Karodus Sub watershed • Using SWAT model the area was delineated into 24 sub watersheds, which were further, divided into 311 HRUs. • Simulated flow at the outlet was compared with the observed flow. Modeling of Cascade Dams & Reservoir Operation

48. Flow Calibration At Karodus Modeling of Cascade Dams & Reservoir Operation

49. Sensitivity Analysis Modeling of Cascade Dams & Reservoir Operation

50. 6. HEC-ResSim (Reservoir System Simulation) Model 6.1. Introduction • HEC-ResSim (USACE) is a modeling software program used to assist in planning studies for evaluating existing & proposed reservoirs, reservoir operations, & to assist in sizing the flood risk management and conservation storage requirements for each project. • It is intended to meet the needs of real-time reservoir regulators for a decision support tool, as well as the needs of modelers doing reservoir projects studies. Modeling of Cascade Dams & Reservoir Operation