The management of dams for drinking water abstraction is complex and has to take into account many parameters. Aside from the reliable provision of raw water in sufficient quantity and quality to supply drinking water to a population, a dam has also to offer sufficient flood control measures. In addition, the ecological quality of the reaches of rivers below a dam has to be considered.
 
Researchers at the Technische Universität Dresden are developing a tool to help dam administrators optimise their water management decisions. It provides possibilities for comparative assessments in particular decision-making scenarios: for example, of the amount of water that should be discharged, when and from what depth, so that enough water remains available in dry seasons; ensuring that there is enough capacity available in periods of intense rain so that flooding does not occur in settlements below a dam; ensuring that captured raw water can be converted into safe potable water cost-effectively using existing water-treatment plants; and that the course of rivers below the dam remain in a natural and ecologically sound condition.

The EU's Water Framework Directive stipulates certain ecological quality requirements; at the same time, water supply engineers also have to consider the costs of water treatment.

At Technische Universität Dresden Prof. Wolfgang Uhl, Chair of Water Supply Engineering of the Institute of Urban and Industrial Water Management is collaborating with Prof. Jürgen Benndorf of the Institute of Hydrobiology and the Ecology Station at Neunzehnhain, an outpost of the university near Lengefeld in the Erzgebirge. The Dresden researchers are furthermore working together with Prof. Dietrich Borchardt of Kassel University and three industrial partners  - a manufacturer of water treatment plants, an engineering consultancy, and a laboratory specialised in front end water analyses.

By analysing weather data and the fill levels of selected dams in relation to their past management, patterns are derived that give information on how such complex systems behave. The project is being led by Prof. Uhl, and is funded by the Bundesministerium für Bildung und Forschung (BMBF) through its Water Technology Agency (PTKA-WTE). Prof. Uhl says that in the next step, future scenarios are to be generated that are typical for particular systems. Effects of climate change can and are to be incorporated. The quality of raw water required for the production of drinking water is then simulated for that particular case. "In the course of the project," says Uhl, "we have developed models where solar radiation, wind, air and water temperature, as the most important parameters, are taken into the calculation of water quality. Thus, we can also allow for long-term trends."
Whether and how the raw water to be expected can be processed into drinking water, and the consequences of management decisions on the ecological condition of the lower courses of the river can then be calculated.

The software tool that is being developed in the course of the project consists of a number of modules. At first, possible szenarios are generated an of these has to be chosen by the user for further analysis. Secondly the fill level of a dam is calculated. The third is concerned with water quality, and the fourth and fifth deal with drinking water processing and the ecological condition of reaches below a dam. The results are compared to given criteria, and then an assessment is made as to whether the chosen management strategy leads to acceptable results, or whether another scenario should be tested.

All the modules of the system are to be combined by the end of 2009. Within the limits of the project targets, it will then be easier to reconcile competing utilizations, and optimise decision-making in the management of dams.

More information:
Prof. Dr.-Ing. Wolfgang Uhl
Faculty Forest, Geo- and Hydrosciences
Institute of Urban and Industrial Water Management
Chair of Water Supply Engineering
ph ++49-351-463-33126