ICOLD Forum: Managing reservoir water quality

Proper management of reservoirs is important to ensure the best possible water quality in the reservoir and in downstream releases. The steps needed to ensure good water quality begin in the planning phase of a dam project, extend through design and construction, and conclude with day-to-day and year-to-year operation of the dam and reservoir.

The many uses of water from a dam for which water quality is important include hydroelectric generation; flood control; navigation; and domestic, industrial, recreational, and agricultural water supply. For the first three uses, water quality must be appropriate for aquatic ecosystems within and downstream from the impoundment. For water supply purposes, quality must be sufficient to meet the requirements for human consumption.

The International Commission on Large Dams (ICOLD) offers a technical bulletin on the topic of reservoir water quality management. Bulletin 128, Management of Reservoir Water Quality — Introduction and Recommendations, was prepared by the ICOLD Committee on the Environment. This committee is made up of 25 members from 23 countries.

The bulletin identifies major physical and biochemical aspects of water quality. It discusses the creation of realistic environmental goals and objectives. Finally, the bulletin provides techniques for managing water quality, including the integration of water quality studies performed during planning, design, construction, and operation of the dam. Various management/enhancement techniques discussed include destratification, oxygenation using the turbine, use of weirs, and construction of multilevel intake structures.

The 111-page bulletin is addressed to all those involved in the design, construction, and operation of dams and reservoirs. To order this bulletin for 41 euros (US$55), visit www.icold-cigb.org 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) 1-40426824; E-mail: secretaire.general@icold-cigb.org.

Microcapsule may help combat zebra mussels

British researchers at the University of Cambridge are studying the effects of a microcapsule containing potassium chloride on zebra mussels.

Zebra mussels are a widespread challenge in water conveyances in western Europe. In their early stages, the mussels can float through water, entering a power plant and attaching to hard surfaces, such as pipes and the shells of other zebra mussels. As the mussels grow, they inhibit the flow of water.

The microcapsule being studied is similar in size to the algae upon which zebra mussels feed. Upon ingestion, the microcapsule releases potassium chloride, which is poisonous to most freshwater mollusks. To protect other freshwater mollusks, zoologist David Aldridge and colleagues engineered the microcapsules so that the coating begins to degrade after a few hours in the water. The microcapsules are introduced directly into the affected pipeline, and they are no longer toxic by the time they reach the outside environment where native mollusk species might live. Other methods of zebra mussel eradication, such as chlorine, have raised concern over harmful ecological side effects.

After conducting successful field trials in the United Kingdom, researchers began large-scale tests in the United Kingdom and North America. Over the winter of 2006-2007, researchers performed tests of the microcapsules with one of the UK’s largest water companies. The first full-scale application of the microcapsules at a waterworks in the UK was planned for mid-2007. The U.S. Fish and Wildlife Service was to conduct independent trials of the microcapsules in the summer of 2007. And tests are planned in Colombia and Brazil to control mussels in water supplies.

Hydro Tasmania studies canal, pipeline coatings

Australian utility Hydro Tasmania is conducting research to determine the best protective coatings for use in refurbishing the interior of water conveyance structures at its 29 hydroelectric facilities. The work is expected to be complete by mid-2008.

In April 2006, the utility began testing several coatings in a water tunnel built at the University of Tasmania. The goal is to determine which coatings will provide the highest rate of flow and lowest amount of biofouling inside penstocks, pipelines, canals, and flumes.

Researchers at the University of Tasmania are using a water tunnel to determine the best protective coatings for use in refurbishing the interior of water conveyance structures. Hydro Tasmania will use the results of this research to upgrade the water passages at its 29 hydro facilities.
Click here to enlarge image

The coatings were chosen as a result of earlier testing to establish biofouling rates on different surfaces. The coatings range from cementitious overlays to paints.

In addition, researchers at the University of Tasmania will use survey modeling techniques to structure 1-meter-square test plates that reflect existing canal and flume surfaces. These plates will be tested to give baseline information on current flow performance.

Results from these water tunnel tests will be applied to hydraulic models used originally to determine current capacities and now to recalculate potential performance improvements. After determining which water passages could benefit from upgrades, Hydro Tasmania will recommend these projects for funding as part of its program to regain lost capacity at existing facilities.

Hydro Tasmania began research on water conveyance linings in 2002. To date, work has involved:

  • Studying the microbiology of the source water;
  • Determining biofouling rates on test panels that replicate a range of surface coatings at Hydro Tasmania’s canals, flumes, pipelines, and penstocks;
  • Using survey techniques to prepare three-dimensional models of concrete-lined canals and flumes; and
  • Conducting full-scale trials of pipeline and penstock internal cleaning to measure efficiency gains (See “Cleaning Water Conveyances: Hydro Tasmania Boosts Power Production,” HRW, July 2006, page 38).

Funding for this research project comes from an A$600,000 (US$428,000) grant from the Australian Research Council. In addition, Hydro Tasmania provides A$87,000 (US$62,000) each year.

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