Modeling of Tekeze Hydropower Reservoir Operation with HEC – ResSim
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Date
2012-04
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Addis Ababa University
Abstract
The main purpose of this study is to model the optimal operation of Tekeze hydropower reservoir for generation of energy and downstream water demand activities considering different scenarios on the power units by accurately determining the reservoir inflow using HEC-ResSim model. The main input data to the model; reservoir physical characteristics, operational characteristics, total monthly irrigation water requirement at downstream of the dam and the hydrological inputs to the reservoir (net evaporation, surface inflow to the reservoirs) are collected and configured. Tekeze dam is located about 80 km west of Mekelle city at coordinates 13° 21‟ North and 38° 45‟ East. To model Tekeze hydropower plant, simulation is performed under three scenarios: (i) the four Francis turbines units are operational, (ii) only three units are operational and (iii) only two units are operational. For each simulation three alternatives are defined on the gate arrangement of the low level outlets to obtain the best alternative that can generate maximum energy. Taking the best alternative, the simulation give for scenario one an average energy of 3669.8MWh and a maximum energy of 7200MWh, for scenario two an average of 3770.7MWh and a maximum energy of 5532.1MWh and for scenario three an average of 3278.1MWh and a maximum of 3641.2MWh. The reservoir level will be almost full in second and third scenario while in the first scenario reservoir level will be below the minimum operating level in the dry season. However, a unique reservoir operation rule curve and power guide curve as operated with the proposed model is developed in this study. Due to the regulation of flow in Tekeze dam, 70.5% in scenario one, 75.5% in scenario two and 81.3% in scenario three of flood occurred in the rainy season is retained by the construction of the dam. Therefore, there is a smooth release throughout the year. Hence irrigation development is possible in the lowland areas of Tekeze which has a total of 42965 hectares net irrigable area. Accordingly the minimum monthly power plant release 58.0m3/s, 98.1m3/s and100.6m3/s when all the four units, only three units and only two units are operational respectively is greater than the monthly peak irrigation demand (45.5m3/s). Therefore irrigation can be developed without affecting power generation to shorten the payback period of the dam and to increase the national economy.