Research

Groundwater is one of the most important sources of drinking water. The use of groundwater as drinking water is mainly made possible by ecosystem services in aquifers. These include natural water purification, which can lead to a reduction in pollutants. These pollutants are mainly introduced into the groundwater by anthropogenic activities. These pollutants also include nitrate, which endangers the groundwater quality in many aquifers, but which can be converted by the ecosystem service of denitrification and thus removed from the groundwater in a natural way. To date, however, this service has been insufficiently taken into account in the management of aquifers and in guidelines, partly because there is a lack of instruments that can be used to clearly determine the potential for denitrification. In addition, denitrification can be spatially and temporally variable and is dependent on changing hydrogeochemical conditions, which are often unknown. Therefore, the main objective of this project is to identify processes and properties that lead to denitrification in groundwater. To achieve this goal, we investigate nitrate sources and denitrification processes in groundwater using isotope techniques. In addition, we identify hydrogeochemical situations that influence denitrification. For this purpose, we carry out monitoring at selected field sites in Austria, France and Denmark as well as controlled experiments under laboratory conditions. For different land use sites, we will investigate effects such as water level, temperature, redox conditions, organic carbon concentrations and chemical pollution on denitrification in groundwater. Together with national and international project partners in France, Denmark and Austria, we are developing a toolbox to better characterize aquifers with regard to their denitrification potential and to develop new protocols that could eventually be integrated into groundwater quality monitoring guidelines. This FWF-funded project is part of the Water4All project “DeepThought” of the Joint Transnational Call “Aquatic Ecosystem Services”.

For grain maize, sugar beet, potato, soybean, sunflower and field vegetables (crop type to be determined), the irrigation requirements of the last 30 years (1995 to 2024) are to be determined for two selected reference areas. The reference areas are selected on the basis of the site conditions (a total of 17 areas are available for selection). The irrigation requirement is determined based on the standard method of the FAO (Allen et al., 1998) in accordance with the state of the art. The required weather data is taken from the Andau weather station (Geosphere Austria data hub). Soil data is taken from the digital Austrian soil map (eBOD). Cultivation data (cultivation dates, stages of development, harvest dates) are provided by the client. Information on cultivation areas from the AMA (freely available) will also be used to estimate the total water requirement. Research questions: How has the plant water demand and the irrigation demand of selected crops at selected locations in the Seewinkel region developed over the last decades? - What would be an optimal irrigation strategy under the given site conditions (climate, soil) and local agricultural crops? - What effects do different weather conditions and irrigation scenarios have on yield? rk steps: - Collection and processing of the required weather data from the Andau weather station (temperature (max, min), humidity, wind speed, radiation and precipitation on a daily basis) and presentation in an annual comparison. - Determination of reference evaporation according to FAO Allen et al. (1998). - Determination of soil properties from the digital soil map (eBOD) and estimation of retention properties (storage capacity) from eBOD (usable field capacity, nFK, of the BAW) and/or using pedotransfer functions. - Determination of plant evaporation and plant water requirements based on standard plant coefficients (Allen et al., 1998). - Determination of the irrigation water requirement for the selected crops for two reference areas, taking into account the plant water requirement and soil properties. Presentation and comparison of the results. - Determination of plant water requirements and irrigation water requirements based on AMA area data. Presentation and comparison of the results.

Climate change increases the frequency and severity of droughts and rainfall events in Austria. The drought-related soil water deficit and the change in rainfall patterns poses a risk for forests, leading to increased tree mortality and loss of ecosystem services. The complex interplay of climate change impacts on trees and the associated response of hydrological components such as precipitation, soil moisture, or runoff is difficult to entangle under temporally-varying, natural conditions. However, detailed knowledge of forest and water interactions are urgently needed in promoting tree-resistance against climate change. Here, we propose controlled manipulation experiments using rain-out shelters and sprinklers to simulate drought and heavy rainfall events in a highly-instrumented, long-term measurement network located in a beech stand of the mountainous Rosalia forest (Lower Austria). We will quantify the percentage of summer and winter precipitation that beech trees transpire, and fluxes of evaporation, transpiration, and groundwater recharge using stable water isotopes. To achieve this, soil and xylem samples will be taken and analysed in the laboratory, and the results of this analysis compared to in-situ high-resolution measurements of soil water and xylem water isotopes using liquid-vapor equilibrium techniques. Further, we will quantify hydrological components using water balance methods and fluorescence tracers. This project will result in estimates of changes in water fluxes under climate change using controlled manipulation experiments as repeated experiments. We will gain insights into forest hydrological changes of Austrian, mountainous beech trees, from which suggestions for forest managers for strategies to promote beech health threatened by increased droughts and heavy rainfalls can be derived.