Climate change impacts on the water balance of the Thaya

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The Thaya with its cross-border catchment area represents an important basis for the water supply as well as the entire water balance and its uses in the border region of Lower Austria and South Moravia. Along the Thaya as a border river there are different uses, such as the water supply of the city of Znaim and other cities, water supply for industrial plants, electricity production by hydropower or agricultural irrigation. In order to optimize the various uses, there are large reservoirs on the Czech side (Vranov, Znaim and Nove Mliny), which regulate the water balance of the catchment area up to the confluence with the March. Due to successive drought years (2017 and 2018), the water management experts of both countries were able to identify for the first time signs of problems in the water supply in the entire catchment area, since the water reservoirs could not be filled in the spring due to the persistent drought. For the first time, extraordinary operational measures had to be discussed within the framework of the Austrian Czech Border Waters Commission in order to be able to continue to ensure the water supply in the region. In the course of the expert discussions, the need was also identified that, although there is exemplary cooperation in the area of ​​flood management, there is a great need for cooperation in the area of ​​drought. For these reasons this project was initiated. The overarching goal of this project is to investigate the effects of climate change on the water balance of the Thaya catchment area up to the year 2050 in order to use this knowledge to develop a bilaterally agreed "emergency" operating regulation. In this regard, the water balance that will be available in the future must be forecast and compared with the future water demand. Existing climate models are brought together for forecasting purposes and climate scenarios are created for the region. For the first time, two neighboring countries are trying to harmonize their specialist knowledge and break it down to a common border region. Based on the results, a bilaterally agreed operating regulation for dry periods will be drawn up as part of the project. This activity will be carried out by the project partners with the support of the experts from the Border Waters Commission and will form the basis for sustainable water supply in the region in times of low water. Due to the cross-border catchment area and the special legal and water management framework, this task can only take place in a bilateral context of the decisive institutions.

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