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Sectors and Themes Water Dams and Development E-paper
Case studiesThe following case studies are introduced here:
The Living Murray (River Murray System, Australia)In March 2001, the Murray-Darling Basin Ministerial Council adopted a vision and set of objectives for River Murray. These have guided the work of the Murray-Darling Basin Commission in addressing the issue of environmental flows in the River Murray System. The vision adopted by the Ministerial Council is: … a healthy River Murray System, sustaining communities and preserving unique values. The following text is taken from The Living Murray website. This document is about what constitutes a healthy working river and what is needed to achieve it. It's about protecting the things the River Murray means to Australians: prosperity, irrigation, industry and clean water, natural landscape, history, culture and tradition. The future of the River Murray has relevance to the whole Murray-Darling Basin. In addressing the environmental needs of the River Murray, the tributaries will have to play their part in providing adequate flows. This will involve the Murrumbidgee and Goulburn Rivers and, although the contribution to the River Murray is smaller, the Darling River above Menindee Lakes. There will be environmental benefits achieved for the tributaries as well as the River Murray through this process. The Living Murray, a Murray-Darling Basin Commission discussion paper about restoring the health of the River Murray and the Murray-Darling Basin. The Living Murray Website forms part of the first stage of informing and engaging the community, beginning in July 2002 and a public entry point for establishing discussion around Environmental Flows and Water Quality Objectives for the River Murray. Implementation of First StepThe Council agreed, as a matter of priority and to inform the COAG National Water Initiative and the development of the Intergovernmental Agreement, that the States and ACT, working with the Commonwealth, agree to identify by 31 May 2004, approaches and priorities to facilitate the expeditious implementation of the Living Murray Initiative, including an approach enabling the early initiation of projects creditable under the National Water Initiative. To advance the First Step of The Living Murray, the Council requested the Commission to:
Initial studies on introducing the concept of environmental flows to the Huong River in Viet Nam.An initiative to provide flood protection to the ancient city of Hue, also led to calls for a more integrated approach to water resources management and the Huong river, including the concept of environmental flows to preserve the important biodiversity of the coastal lagoon. It is part of IUCN's Water and Nature Initiative (WANI). Modifying Dam Design for Flood Releases - Tana River, KenyaThe following information was prepared by Mike Acreman as an example of lessons learned for the UNEP-DDP database. The Tana River is the largest in Kenya. It rises in the highlands near Nairobi and Mt Kenya and then flows for more than 250 km over the flat, dry coastal plain to the Indian Ocean. The Tana has an extensive floodplain and delta, which is the mainstay for thousands of people who use the results of the floods for their survival through subsistence agriculture, fishing, livestock rearing and horticulture. The wetlands of the lower floodplain and delta are the main refuge of livestock and wildlife from a wide area that is extremely arid for most of the year. Planning is underway to dam the Tana upstream of the floodplain at Mtonga (or Grand Falls) to accommodate several hydropower plants to satisfy the increasing electricity demand within Kenya. Investigations by the designers and developers have shown that the floodplain and its floods are a very significant resource both locally and nationally and that they should be retained if possible. Consequently, a dam is being designed that will store enough water to produce a flood downstream through substantial releases as well as produce the necessary electricity. Furthermore, recognising that silt is as important as water for the maintenance of the productivity of the floodplain, the dam designer s are looking at the potential for releasing silt together with the flood water. Apart from the engineering details, the main problem faced by the engineers is inadequate knowledge of the amount of water required to simulate a flood and the timing of this in relation to upstream and local rainfall. The lower Tana is not a simple channel that overflows onto the floodplain. Furthermore, the contribution to flooding from parallel channels, from short-lived local streams and from subsurface flows is still poorly understood. However, a modelling study is currently underway to address these limitations using data from historical and recent floods. These data show that similar "normal" floodplain inundations (as measured by the flood hydrograph at Garissa) have resulted from a range of different flows from the dam site. The flood release hydrographs to be chosen can vary enormously in volume, which can all produce the desired flood downstream depending on the hydrological conditions in the rest of the catchment. This means that regional rainfall, soil moisture and flows from tributaries must all be monitored if the optimum release is to be made. Despite this complexity, it is anticipated that the final design will result in a dam that meets the demand for electricity and respects the needs of its floodplain downstream. Fisheries data in the Mekong River BasinFisheries is an important source of income and nutrition for the people of the Mekong River Basin. Over a number of years a better understanding has been developed of the fish, their habitats and migration patterns and their role in the social, economic and cultural setting of the basin. A number of reports are available from the MRC website including:
These have been supplemented by project specific studies, for example for the Nam Theun 2 project in Lao PDR - annual report of the pre-impoundment studies for the Xe Bang Fai.
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