Durch systematische Geländeuntersuchungen über 15 Monate an zwei Brunnengalerien der Berliner Wasserbetriebe wurde untersucht, ob und inwieweit kontinuierliche Temperaturmessungen entlang der Fließstrecke des Grundwassers geeignet sind, die Aufenthaltszeit so zuverlässig zu bestimmen, dass ein kritisches Unterschreiten der 50-Tage-Linie erkannt und entsprechende betriebliche Gegenmaßnahmen im Routinebetrieb eingeleitet werden können. Die Temperaturmessung erfolgte kontinuierlich mittels Datenloggern in Entnahmebrunnen und Grundwassermessstellen und zusätzlich manuell bei wöchentlichen Probenahmen. Zeitreihen konservativer Tracer (Chlorid, Bromid, d18O und d2H) dienten der Validierung der aus den Temperaturmessungen bestimmten thermischen Retardations- und Dispersionskoeffizienten. Trotz signifikanter Unterschiede zwischen den beiden untersuchten Standorten erwiesen sich die Temperaturmessungen als geeignetes Instrument zur Bestimmung der Verweilzeiten. Aus den untersuchten Tracern konnten darüber hinaus Aussagen zum Mischungsverhältnis von angereichertem und autochthonem Grundwasser abgeleitet werden.

Different types of managed aquifer recharge (MAR) schemes are widely distributed and applied on various scales and for various purposes in the European countries, but a systematic categorization and compilation of data has been missing up to now. The European MAR catalogue presented herein contains various key parameters collected from the available literature. The catalogue includes 224 currently active MAR sites found in 23 European countries. Large quantities of drinking water are produced by MAR sites in Hungary, Slovakia, the Netherlands, Germany, Finland, Poland, Switzerland and France. This inventory highlights that, for over a century, MAR has played an important role in the development of European water supply and contributes to drinking-water production substantially. This development has occurred autonomously, with “trial-and-error” within the full range of climatically and hydrogeologically diverse conditions of the European countries. For the future, MAR has the potential to facilitate optimal (re)use and storage of available water resources and to take advantage of the natural purification and low energy requirements during MAR operations. Particularly with respect to the re-use of wastewater treatment-plant effluent and stormwater, which is currently underdeveloped, the use of MAR can support the public acceptance of such water-resource efficient schemes. Particularly for the highly productive and urbanized coastal zones, where the pressure on freshwater supplies increases by growing water demand, salinization and increased agricultural needs for food production (such as along the Mediterranean and North Sea coasts), MAR is expected to be increasingly relied on in Europe.

Subsurface travel time from the area of recharge to the abstraction during Managed Aquifer Recharge (MAR) is a critical parameter to ensure sufficient attenuation for hygienic parameters and other undesired substances. This study investigates seasonal temperature fluctuations observed in recharge water and MAR wells as a proxy for cheap and reliable travel time control at a basin infiltration site in Berlin-Spandau (Germany). Based on a time series from seven years of manual measurements, temperature fluctuations observed in infiltration basins and abstraction wells were fitted to sinusoidal functions. Peak values represented as local maxima and local minima from the fitted curves were used for the approximation of travel times between infiltration basin and abstraction wells. Uncertainty was assessed by Monte Carlo simulation of fitted curves based on standard deviation (2s) from residuals. The calculated error propagation from 2s in infiltration basin and 2s in wells range from 7 to 19 days. This study indicates that travel time approximation based on biased manual measurements of temperature is associated with high uncertainty. Nevertheless, the water temperature method for estimating subsurface travel times shows encouraging results and if temperature can be accurately determined, this method can be readily applied at other sites with similar characteristics.

The paper presents semi-analytical mathematical model to estimate unsteady groundwater recharge resulting from variable depth of water in a large water body, influenced by time variant inflows and outflows. The model has been derived by integrating Hantush’s (1967) analytical expression for water table rise due to recharge from a rectangular spreading basin into the water balance equation of the water body. The model has been applied to a test study site in Raipur (India) for assessing viability of Managed Aquifer Recharge (MAR) from a lake located on an area dominated by the massive limestone formation. The components of the water balance equation have been carried out by the comprehensive analysis of the hydrological and hydrogeological aspects of the lake. The hydrological components include

This project report summarizes work conducted in work package 11. Along with the deliverable 11.1 and milestone report 11 it covers the tasks from work package 11 as formulated in the Description of Work (DoW). The content of the different sections is interrelated, but each section is organized as an independent part. Title of this report differs from DoW because recommendations for optimum design and operation will be handled in the deliverable 12.2. The sections in this report cover various topics and each section can be found as a stand-alone report in the DEMEAU tool box (http://demeaufp7.eu/toolbox/) for download. Detailed summaries can be found for each section separately.

Emerging subsurface activities (ESA) describe a set of methodologies and technologies using the earths subsurface for energy production or capture and storage of carbon dioxide. The earth’s heat is used as a clean source of energy (deep geothermal systems, DGS), process-related CO2 emissions can be stored in suitable geological formations (geological CO2 storage, GCS) and since the technique of horizontal drilling was developed, the exploitation of unconventional reserves of natural gas via hydraulic fracturing (shale gas extraction, SGE) expanded. At the same time, 97% of global freshwater resources are stored in the earth's subsurface, too, so that exploitation interests may come into conflict with the issue of groundwater and environmental protection. Main objective of deliverable D 3.1 of the COSMA-1 project therefore was to identify best practices of monitoring for geological carbon storage, deep geothermal systems and shale gas extraction projects with special focus on groundwater protection. Chapter 2 summarizes current groundwater monitoring standards, including monitoring network designs for emission-based (operators) and immission-based (water suppliers) monitoring. It further presents an identification of hazards related to ESA and a brief overview about the state of regulation. Finally, knowledge gaps concerning groundwater protection are identified. Chapters 3 to 5 describe for each of the above-named types of ESA the project stages and according monitoring needs and methods. Main target was to identify the key parameters and monitoring network designs ensuring reliable groundwater monitoring. As the most relevant hazards were drilling fluids, fracking fluids and brine migration as well as the mobilisation of methane, and the most likely pathways are leakages due to insufficient well integrity, for all three ESA types, pressure, temperature and TDS were recommended as key monitoring parameters. For shale gas extraction, in addition methane emission should be monitored. Key to any monitoring is i) the baseline sampling prior to the start of subsurface activities and ii) the adequate delineation of the area of review. All further monitoring to be implemented base on site-specific considerations and the authorities’ priorities. In any case, monitoring network should include the up-gradient, down-gradient and depth component. Monitoring wells and equipment should cover the full extension of horizontal bores and additional wells should be placed above potential pathways for fluid (or brine) migration as e.g. fault systems. The use of abandoned wells for monitoring is also recommended. The conception of appropriate monitoring strategies has further to be coordinated with the competent authorities, which have to control the compliance with all requirements. Therefore, site operator and water producer should report their monitoring plans and data at regular intervals to the competent authorities. The findings were summarized by transferring them to a risk management matrix following the Water Safety Plan (WSP) approach (WHO 2009). For shale gas extraction, deliverable D 3.2 will add specific mitigation measures to reduce the previously identified risk of negative impacts on shallow groundwater. Geological carbon storage was further investigated by means of the development of a coupled model for a theoretical case study site in the North-Eastern German Basin in the scope of work package 2 of the COSMA-project (D 2.3).