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Multipurpose Water Resource Planning And Management Using Nile Basin Dss Case Study: - Tana Sub Basin, Ethiopia

Congress: 2015
Author(s): Habtam Achenef (Bahir Dar, Ethiopia)


Keyword(s): Sub-theme 10: Management of water resources,
AbstractHabtam Achenef Mekonen Water Resource Specialist I have professional experience in areas of water balance and allocations, soil and water conservation, water supply and sanitations, water harvesting, large scale irrigation project as water resource management engineer constructed by support of Africa Development Bank, water resource planning and management specialist supported by World Bank, head of water management department and water resource management specialist at Abay Basin Authority. BSc and MSc in areas of Water Resource Engineering (Engineering Hydrology) Abay Basin Authority Bahir Dar, Ethiopia habt.ache@yahoo.com Key Words: Nile Basin DSS, Tana Sub Basin, Scenarios, Indicators, Melt-criteria Analysis Background The Lake Tana Sub Basin has a drainage area of 15083 sq. Km, including lake surface area of 3000 sq. km. The lake is the source of Blue Nile River and total storage capacity of 32,000mcm with a useful storage capacity of 8,500mcm. Water resources planning for the Tana Sub-Basin need to take into account the various, often conflicting, water needs of the economic sectors and the environment. The Government of Ethiopia established the Abay Basin Authority to promote water resources planning and management at local level; the Authority was established in (Reg. 151/2008). As part of its key initial activities, the Authority is embarking on developing a multi-sector water resources plan for the Tana Sub-Basin. The Authority is carrying out a study using the Nile Basin Decision Support System (NB-DSS) to providing the inputs needed for a water resources management and development plan for the Tana Sub-Basin. Objective: To evaluate the impact of large scale irrigation development on *Hydro power production, *Fish Production on the Lake Tana *Evaporation system wise *Lake Navigation Methodology and Approach Mike Hydro was selected from Mike Zero for simulation of data from 1960 to 2005 and scenarios for development interventions. Within this context, the objective of this pilot case application for the Tana Sub-Basin was to undertake scenario evaluation using the NB-DSS. This involved the configuration, calibration and validation of a relevant baseline model for representing the present state of water resource development for the pilot application case, defining scenarios and a set of economic, environmental and social evaluation criteria (indicators), using the configured model implemented scenarios in the NB-DSS and employed the MCA tools and associated functionality embedded in the NB-DSS evaluated scenarios based on the quantification of economic, environmental and social indicators. However indicators like Hydro power Generation with flow, Navigation with Lake water level, and Fish Production with lake water surface area and Evaporation with the system were used. Key findings  Comparing the base case and the worst case scenarios the Tana Beles hydropower product decreases by 16% annually, this indicates that the impact of irrigation development have little impact on the power generation but the study indicates that, this amount of power production have been incorporated in the design of upstream dams of the sub basin.  As seen from the result of indictor regarding fish production in the Lake, Comparing the base case and the worst case scenarios of fish production, there is an insignificant loss in the sector because it is declining annually by 1% only.  But the irrigation development in the future will have a greater influence on the Lake navigation; this can be shown by an increase in the number of days per year where the lake level decreases below 1785 masl where navigations blocked from (35 to 141) days/year. Though this values do not shows how many consecutive non-navigable days are present, it is a reasonable assumption to take most of this decrease in lake level happens in the dry seasons of the year. 141 non-navigable days have a greater socio-economical impact.  The increase in the reservoir development on the total water surface evaporation of the system is insignificant, the result shows that development in the sub-basin have a smaller impact by increasing the amount of water surface evaporation from the sub-basin, the reason can be explained by the fact that the evaporation & rainfall of the u/s dams are almost balanced and the development also increase the surface area that is exposed to evaporation at the lake body but at scenario three utilization of water resource using pump irrigation from the lake makes it decrease due to minimizing of open surface water area of the lake. During Stakeholder consultation of melt-criteria analysis, scenario two has been selected Conclusions Based on the findings, the development of large scale irrigation projects of koga, Ribb, Megech, Gilgel Abay, Jemma, Gumara and lake Tana Pump have no significant effect on evaporations, fish productions and hydropower power generations and also studies show that, some of the dams will have power as well as fish production plan equivalent to the decline amount to be able to compensate the productions. But for navigation it needs some amount of water during dryer period because due to those development interventions the lake level can lower below the average up to 5 months/year of the dryer period. Based on the MCA all irrigation projects are preferred except pump irrigation. Recommendations Operation rules of the dams should consider navigation during the dry period, with this result; it has to be able to do further with more indicators and even by CBA method of analysis by considering other sub basin water resource actors. All levels of stakeholders should participate all the way, starting from the early beginning to the implementation process. For further work a lot of data are collected and are organizing, and also scripts are developing. Experience sharing and training with Nile Basin Initiative.
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