Towards an improved understanding of transport processes governing the spatiotemporal dynamics of particles and fecal bacteria in karst aquifers – IMPART
Final Report Abstract
Karst aquifers provide drinking water for 9.2% of the global population. The generally good water quality is often interrupted by rapid and strong contamination events. To understand the detailed transport processes and spatiotemporal changes in water quality the IMPART project was conducted at Germany’s second largest karst spring (Blautopf). Deeper insight into the structure of the karst system was gained by two large scale tracer tests, with a total of 7 tracer injections at the surface and inside the active conduit network, and monitoring locations in the cave system and at the spring. The results demonstrated that the catchment can be subdivided into two sub-catchments of similar size and allowed to quantify the variability of transport velocities, which were up to three times higher at high-flow than at low-flow conditions. Sediment particles play a significant role as transport vectors for contaminants. A comparative tracer test using suspended cave sediments and solute tracers, along with detailed geochemical analyses, revealed that sediment particles were transported faster than solutes, which is explained by preferential transport along the main flow paths of the conduit. All particle sizes (< 10 µm) were transported similarly, and a sediment-associated transport could be demonstrated for all geochemical elements. The results represent an important step forward as they lead to a deeper understanding of the transport processes of sediment-bound pollutants. The comprehensive investigation of the water quality by means of a 30-month long-term monitoring, intensive sampling of a rainfall event and a spatial sampling within the cave system, demonstrated that the spring exhibits only moderate seasonal variations, but shows a strong response to intense precipitation events, e.g., fecal bacteria (E. coli) increased 100-fold (up to 17,168 MPN/100 ml) during a monitored event. A paired-catchment approach was successfully implemented for the first time to a subsurface karst- and cave system. Chemical and microbial water quality differed significantly between both sub-catchments and could be associated to different land use. Nitrate was linked to agriculture whereas potassium, chloride, gadolinium and fecal bacteria could be identified as indicators for waste water effluents. This study underlines the susceptibility of karst springs and demonstrates the applicability of spatial-temporal water quality monitoring as a powerful tool to identify impacts of land use activities. Additionally, the discharge behavior of Blautopf was analyzed for historic and future responses to climate change. Historic time series (1952–2021) of climate variables and discharge were statistically evaluated and used to calibrate a reservoir model, which was then used to simulate the expected impacts of climate change on spring discharge. Results show no significant changes for annual mean and low discharge in the historic data, but the annual peak discharge shifted to a lower state since 1988 due to decreasing precipitation, decreasing snowmelt and increasing air temperature. According to the projections of all climate-change scenarios, peak discharge may decrease by 50% and baseflow by 35–55% by 2100 due to increasing evapotranspiration and decreasing snow cover. Results show the prolonged impact of climate change and variability on the floods and droughts at the springs and may imply water scarcity risks at similar climatic and geologic settings.
Publications
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Kann man das trinken? Untersuchung zur Dynamik der Wasserqualität am Blautopf in Blaubeuren. Lecture Series at Karlsruher Institute of Technology (KIT): Junge Talente - Wissenschaft und Musik, 14 October 2021
Mueller Y.K.
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Eurokarst Málaga 22nd-25th of June 2022. Quantifying the response of karst discharge to long-term climate variations at Blautopf spring
Fan X., Goeppert N. & Goldscheider N.
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New insights into water-quality dynamics using a novel pairedcatchment approach inside a karst and cave system in Southern Germany (Blautopf). Eurokarst Málaga 22nd-25th of June 2022
Müller Y.K., Goeppert N. & Goldscheider N.
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From cave to spring: Understanding transport of suspended sediment particles in a fully phreatic karst conduit using particle analysis and geochemical methods. Hydrological Processes, 37(10).
Mueller, Yanina K.; Goldscheider, Nico; Eiche, Elisabeth; Emberger, Hanna & Goeppert, Nadine
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Neue Erkenntnisse zur Hydrogeologie im Blauhöhlensystem. 11. Symposium Verkarstung in Süddeutschland, 18 November 2023
Mueller Y.K., Goeppert N., Tiefenbacher M. & Goldscheider N.
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Quantifying the historic and future response of karst spring discharge to climate variability and change at a snow-influenced temperate catchment in central Europe. Hydrogeology Journal, 31(8), 2213-2229.
Fan, Xinyang; Goeppert, Nadine & Goldscheider, Nico
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29. Tagung der Fachsektion Hydrogeologie (FH-DGGV) Aachen 20th- 23rd of March 2024. Analyse der historischen und Prognose der zukünftigen Quellschüttungen des Blautopfs unter der Bedingung des Klimawandels
Goldscheider N., Fan X. & Goeppert N.
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29. Tagung der Fachsektion Hydrogeologie (FH-DGGV) Aachen 20th- 23rd of March 2024. Verbessertes Verständnis detaillierter Sediment- und geochemischer Transportprozesse durch einen vergleichenden Markierungsversuch
Mueller Y.K., Goldscheider N., Eiche E., Emberger H. & Goeppert N.
