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Evaluating decision support systems for dams

A study is under way in Africa to evaluate existing decision support system (DSS) tools and their applicability for planning and operating dams. Based on their findings, researchers say they will develop and disseminate guidelines describing which DSS tools work best when evaluating economic, social, and environmental effects of dams. The guidelines also will provide information on how DSS tools can be used to incorporate stakeholder input in the planning and operation of large dams.

The study is a component of the Consultative Group for International Agriculture Research’s Challenge Program for Water and Food. Partners in the study are the Ethiopian Ministry of Water Resources, Addis Ababa University in Ethiopia, the International Water Management Institute in Ethiopia, and South African environmental flows consultant Southern Waters.

Research began in 2005 and is expected to be complete by 2008.

Matthew McCartney, researcher with the International Water Management Institute, is managing the study. “In recent years, considerable effort has gone into developing DSS tools to assist water resource managers in making well-informed decisions,” says McCartney.

“However, with a few exceptions, these have largely focused on the technical, engineering, and economic aspects of dam operation, with little consideration of social and environmental issues. We are studying how DSS tools can also be used to make decisions about how to most effectively mitigate negative social and environmental effects of a dam.”

“DSS tools consist of computer software or other systems used to make decisions about how to allocate water,” says McCartney.“The decisions can be associated with strategic planning for a proposed dam or with day-to-day operation of an existing dam. A DSS may contribute to either type of decision or both; it may encapsulate the entire decision-making process or it may contribute to only a single aspect of either planning or operation.”

For this study, the research team is testing several DSS tools by applying them to the Chara Chara and Koga dams in Ethiopia and to the Nalubaale-Kiira Complex in Uganda.

Chara Chara Dam is a diversion weir, built in the mid-1990s across the Abay River at the outlet of Lake Tana to regulate outflow from the lake. The weir provides water for hydroelectric generation at the 11.4-mw Tis Abay I and 73-mw Tis Abay II powerhouses.

Koga Dam is being built in the catchment of Lake Tana. It will store water to irrigate agricultural land.

The Nalubaale-Kiira complex consists of two hydroelectric projects with a total capacity of 260 mw on the White Nile River, just downstream from Lake Victoria.

In applying existing DSS tools to investigate the planning and operation of these three dams, McCartney says his team looks at the following areas:

“Ultimately, we hope to demonstrate the value of decision support systems in contributing to improved development outcomes, ensuring public acceptance, and reducing conflict related to dam planning and operation,” McCartney says.

– For further information about the study, contact Mr. McCartney at (251) 11-6461252; E-mail: m.mccartney@cgiar.org.


ICOLD Forum:Advances in RCC

Many notable advances in the use of roller-compacted-concrete (RCC) technology for dam construction have occurred over the past three decades.

Click here to enlarge image

The evolution of this technology includes development and application of the rolled concrete dam (RCD) in the 1970s in Japan; the low cementitious content concept in Australia and the United States in the early 1980s; and the use of higher cementitious content in Spain, China, and other countries in the mid 1980s.

China pioneered the use of RCC in arch dams, France advocates the use of “hardfill” RCC concepts, and Brazil uses “high fines” in the majority of its dams. Current concepts range from the “lean” (low cementitious content) RCC dam, to the RCD method developed in Japan, to the “high-paste” (high cementitious content) RCC dams.

Using RCC for dam construction is attractive because it reduces the costs of building a concrete dam and shortens construction time over more traditional methods of concrete placement.

Issues of interest regarding RCC include: design considerations (such as seismic aspects and temperature control), materials (such as aggregates, cementitious materials, and admixtures), mix proportions, construction (such as transportation and compaction), quality control, and performance.

The International Commission on Large Dams (ICOLD) offers a technical bulletin on the topic of RCC. Bulletin 126, Roller-Compacted Concrete Dams — State of the Art and Case Histories, was prepared by ICOLD’s Committee on Concrete for Dams. This committee is made up of 20 dam engineering professionals from 19 countries.

The 312-page technical bulletin contains eight case histories of RCC dams, as well as a list of all RCC dams completed and under construction, through 2001. To order this ICOLD bulletin for 70 euros (US$92), visit www.icold-cigb.net and click on Publications, then Bulletins.

– ICOLD is a nongovernmental organization that provides a forum for the exchange of knowledge and experience in dam engineering. The organization leads the profession in ensuring that dams are built safely, efficiently, economically, and without detrimental effects on the environment. To learn more about ICOLD activities, contact Michel De Vivo, Secretary-General, ICOLD 151, Bd Haussmann, Paris 75008 France; (33) 1-404426824; E-mail: secretaire.general@icold-cigb.org.


Retraction

Important information in an item published in the “Tech Notes” department of the September 2006 issue of HRW is incorrect. We have learned that the story, “New lining method to reduce seepage in tunnels” (page 42), does not accurately describe practices at the Enguri hydroelectric project in Georgia and, in fact, contains serious errors. Readers are therefore advised to wholly disregard the information presented in this article. We sincerely regret this occurrence.


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