Multiobjective Operation of Zambezi River Reservoirs (original) (raw)
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Analysis of future hydropower development and operational scenarios on the zambezi river basin
2016
The Zambezi River basin is the fourth largest in Africa. Covering an area of about 1 400 000 km2 that is shared among 8 countries, it is the home of over 30 million people. There are ample opportunities for development in the region, including on the hydropower sector, whose estimated potential still to be exploited amounts to over 8 000 MW. In the future, the Zambezi is thought to be particularly vulnerable to climatic changes, with sizable expected impacts on average runoff, and will play a key role in the challenges posed by regional water scarcity. How future and current hydropower schemes are laid out and operate will affect the valuable ecosystems still thriving in the riparian areas of the basin and impact economic, as well as societal aspects. The present contribution employs a daily flow routing model in order to evaluate the impacts of different future hydropower development scenarios on the Zambezi River basin. Resorting to it and a multi-objective optimization technique ...
Analysis of flow regime changes due to operation of large reservoirs on the Zambezi River
2010
The Zambezi Basin, a semi-arid 1.4 Mio km 2 catchment area spreading across eight countries, constitutes a highly complex system. With several large dams, namely Kariba, Cahora Bassa, Kafue Gorge and Itezhi-Tezhi, the basin's hydrology is also influenced by vast wetlands with high ecological value such as the Barotse plains, the Mana Pools or the Kafue flats. The African DAms ProjecT (ADAPT) is an interdisciplinary research project aiming to develop an integrated set of methods that help assessing the ecological and socio-economic effects of dams. A comprehensive evaluation and characterization of the flow regimes before and after the dam's construction is a stepping stone towards this goal. The analysis is based on historical data, taking into account the evolution of existing reservoirs and hydropower plants. Three indicators are considered to describe the flow regimes in the basin. They allow quantifying the seasonal transfer of the water, the subweekly flow fluctuations and the intensity and frequency of the flow changes. In a further stage, a semi-distributed conceptual hydrological model will be built to simulate the flow regime with and without dams for actual and future hydrological scenarios.
Water Policy, 2012
The Zambezi river basin is of utmost importance to its riparian countries in terms of energy, food production and natural resources. Even though there is no legal agreement on the sharing of Zambezi waters, an assessment of basin-wide economically efficient allocation policies will provide valuable information at a time where water managers and policy makers in the region are negotiating the establishment of a unified river basin institution, called the Zambezi Watercourse Commission (ZAMCOM). That institution would be responsible for, amongst other things, the design of allocation rules. In this study, basin-wide allocation policies are derived from a hydroeconomic model that considers the largest existing and planned hydraulic infrastructure and irrigation schemes in the basin. Our results illustrate that the economic value of water varies spatially, driven primarily by large changes in elevation and on the locations of existing or proposed dams. This observation may have implications for future decisions about the siting of expansions in irrigated agriculture. For example, some of the planned irrigation schemes in upstream countries are not economically sound if the power stations that are in an advanced planning phase are implemented. This study also reveals that the economic value of the three largest storage infrastructure (Kariba, Itezhitezhi, Cahora Bassa) is around US$443 million/year.
Optimal flow allocation in the Zambezi River system
Water Resources Management, 1997
The optimal flow allocation in the Zambezi system, the largest multi-reservoir water resources system in southern Africa, is analysed. The problem is formulated in network terms and solved with a network flow algorithm. The present configuration of the system is taken as the reference to evaluate the benefits of the proposed modifications to the existing hydropower schemes. The introduction of additional operational constraints is also considered in order to analyse the costs of environmental protection of paludal ecosystems and to account for secondary objectives (e.g. irrigation, fishery, navigation). The results show that the upgrade of Kafue Gorge scheme through the addition of a new generator stage is the most advantageous from the hydropower production view point. In addition, the protection of paludal ecosystems through periodic controlled flooding and an increase of withdrawals for irrigation purposes may be achieved without dramatically changing the hydroelectric energy production.
Optimising hydropower development and ecosystem services in the Kafue River, Zambia
Marine and Freshwater Research
Fisheries are an important resource in Zambia, but are experiencing overexploitation and are under increasing pressure from external development activities that are compromising river ecosystem services and functioning. One such system is the Kafue Flats floodplain, which is under threat from hydropower development. This paper reviews the effect of potential hydropower development on the Kafue Flats floodplain and explores mechanisms to optimise the expansion of hydropower while maintaining the ecosystem functioning and services that the floodplain delivers. Since completion of the Kafue Gorge and Itezhi-tezhi dams, seasonal fluctuations in the height and extent of flooding have been suppressed. This situation is likely to get worse with the proposed incorporation of a hydropower scheme into Itezhi-tezhi dam, which will operate under a hydropeaking regime. This will have major ramifications for the fish communities and ecosystem functioning and is likely to result in the demise of t...
Physics and Chemistry of the Earth, Parts A/B/C, 2017
The Government of the Republic Zambia (GRZ) will install a new hydropower station Kafue Gorge Lower downstream of the existing Kafue Gorge Station (KGS) and plans to start operating the Itezhi-Tezhi (ITT) hydropower facility in the Kafue Basin. The Basin has significant biodiversity hot spots such as the Luangwa National park and Kafue Flats. It is described as a Man-Biosphere reserve and the National Park is a designated World Heritage Site hosting a variety of wildlife species. All these natural reserves demand special protection, and environmental flow requirements (e-flows) have been identified as a necessary need to preserve these ecosystems. Implementation of e-flows is therefore a priority as Zambia considers to install more hydropower facilities. However before allocation of e-flows, it is necessary to first assess the river flow available for allocation at existing hydropower stations in the Kafue Basin. The river flow availability in the basin was checked by assessing the variability in low and high flows since the timing, frequency and duration of extreme droughts and floods (caused by low and high flows) are all important hydrological characteristics of a flow regime that affects e-flows. The river flows for a 41 year monthly time series data (1973 to 2014) were used to extract independent low and high flows using the Water Engineering Time Series Processing Tool (WETSPRO). The low and high flows were used to construct cumulative frequency distribution curves that were compared and analysed to show their variation over a long period. A water balance of each hydropower station was used to check the river flow allocation aspect by comparing the calculated water balance outflow (river flow) with the observed river flow, the hydropower and consumptive water rights downstream of each hydropower station. In drought periods about 50 to 100 m 3 /s of riverflow is available or discharged at both ITT and KGS stations while as in extreme flood events about 1300 to 1500 m 3 /s of riverflow is available. There is river flow available in the wet and dry seasons for e-flow allocation at ITT. On average per month 25 m 3 /s is allocated for e-flows at ITT for downstream purposes. On the other hand, it may be impossible to implement e-flows at KGS with the limited available outflow (river flow). The available river flow from ITT plays a very vital role in satisfying the current hydropower generating capacity at KGS. Therefore, the operations of KGS heavily depends on the available outflow (river flow) from ITT.
Article, 2023
This study was conducted within the Zambezi River Basin to ascertain the bathymetry and sedimentation of selected reservoirs, evaluate their seasonal hydrological regimes, pinpoint the causes of reservoir siltation, and determine how the bathymetry and siltation impacted water-related industries and policy choices. Hydrological field measurements using a hydrographic survey boat, document studies, and interviews were used to collect the data. The 3D spatial analyst tools in ArcGIS 10.3 and hypsometric curves were used to analyze bathymetric data. Thematic analysis was used to analyze qualitative interview data. Findings indicated that sedimentation was a problematic phenomenon spatial-temporally and, it triggered a significant decrease in the storage capacities of the reservoirs. The study noted that catchments with small reservoirs were vulnerable to severe water stress, particularly from July through the beginning of the next rainy season in December. Over 90% of the local population and water-related industries were facing substantial risks of economic water shortages and may continue to face more water challenges amidst escalating climatic changes. The problem could be addressed by coping mechanisms such as alternative livelihoods, water harvesting, and water shedding. This study proposes an Integrated Water Resources Management Framework, which may help incorporate water education to bring about behavioural change against drivers of sedimentation. The proposed sediment and water resources management model serves as a multidisciplinary and transdisciplinary tool that could be used to address siltation concerns. This work has also shown the significance of bathymetric surveys of small reservoirs as a basis for policy context and regulations on managing water resources.