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In this study, the potential of machine learning (ML) for shallow groundwater level predictions in urban areas is explored. It focuses on curating a training dataset that represents the spatial variability of the water table depth, tests the effect of using different feature variables in ML modeling, and finally, compares two ML models with a physically-based (PB) urban hydrological model. To curate a consistent training dataset, a method of transferring low-frequency groundwater level measurements to a minimum water table depth (MWTD) was developed. Two ML models, one with national maps as feature variables and the other including local high-resolution urban feature variables, were trained against the same 280 groundwater level data points and applied to predict the MWTD at a 10 m spatial resolution for the city of Odense, Denmark. The ML models reached a similar fit to the observations, with an RMSE of 1.1 m and 1.3 m, respectively, and outperformed the urban PB model. In densely urbanized areas, the ML models and the PB model showed up to a 1.5 m difference in predictions of MWTD. The results suggest that ML modeling has the potential to provide spatially high-resolution predictions of the shallow groundwater table in urban areas, which represents a challenge for PB models because of their model structure and the lack of hydrological knowledge hindering meaningful parameterization schemes. Furthermore, a SHapley Additive exPlanation (SHAP) analysis of the feature variables illustrates that ML models can be utilized to explore the hydrological relations in urban domains, by analyzing the feature variables’ relations.

In this study, the potential of machine learning (ML) for shallow groundwater level predictions in urban areas is explored. It focuses on curating a training dataset that represents the spatial variability of the water table depth, tests the effect of using different feature variables in ML modeling, and finally, compares two ML models with a physically-based (PB) urban hydrological model. To curate a consistent training dataset, a method of transferring low-frequency groundwater level measurements to a minimum water table depth (MWTD) was developed. Two ML models, one with national maps as feature variables and the other including local high-resolution urban feature variables, were trained against the same 280 groundwater level data points and applied to predict the MWTD at a 10 m spatial resolution for the city of Odense, Denmark. The ML models reached a similar fit to the observations, with an RMSE of 1.1 m and 1.3 m, respectively, and outperformed the urban PB model. In densely urbanized areas, the ML models and the PB model showed up to a 1.5 m difference in predictions of MWTD. The results suggest that ML modeling has the potential to provide spatially high-resolution predictions of the shallow groundwater table in urban areas, which represents a challenge for PB models because of their model structure and the lack of hydrological knowledge hindering meaningful parameterization schemes. Furthermore, a SHapley Additive exPlanation (SHAP) analysis of the feature variables illustrates that ML models can be utilized to explore the hydrological relations in urban domains, by analyzing the feature variables’ relations.

Estimation of groundwater travel time distribution (TTD) is critical to environmental assessment and successful urban water management. This paper presents a novel analytical approach to account for the groundwater TTD in an unconfined aquifer, considering the impervious urban structure and the modified aquifer hydraulic properties due to consolidation processes. The analytical solution follows the Dupuit-Forchheimer assumption and is verified through comparisons with numerical results. Sensitivity study reveals a potential increase in the mean travel time when the aquifer intersects with an impervious underground structure, while the degree of change depends on the interplay of two mechanisms (i.e., the increase in upgradient groundwater storage and the decrease in pore space of the consolidated zone). Global sensitivity analysis suggests that urban groundwater TTD systems are strongly dependent on both construction-related parameters and aquifer compressibility, indicating that adaptive strategies of groundwater management should be taken for different aquifer types. The proposed analytical model has great implications for the management of water resources in urban areas, the utilization of urban groundwater for human consumption, and the quality of urban aquifers.

Low-enthalpy geothermal energy (LEGE) is a carbon-free and renewable source to provide cooling and heating to infrastructures (e.g. buildings) by exchanging their temperature with that of the ground. The exchange of temperature modifies the groundwater temperature around LEGE installations, which may contribute to enhancing the capacity of aquifers to degrade organic contaminants of emerging concern (OCECs), whose presence is significantly increasing in urban aquifers. Here, we investigate the impact of LEGE on OCECs and their bioremediation potential through numerical modelling of synthetic and real-based cases. Simulation results demonstrate that: (i) LEGE facilities have the potential to noticeably modify the concentrations of OCECs; and (ii) the final impact depends on the design of the facility. This study suggests that optimized LEGE facility designs could contribute to the degradation of OCECs present in urban aquifers, thus improving groundwater quality and increasing its availability in urban areas.

Estimation of groundwater travel time distribution (TTD) is critical to environmental assessment and successful urban water management. This paper presents a novel analytical approach to account for the groundwater TTD in an unconfined aquifer, considering the impervious urban structure and the modified aquifer hydraulic properties due to consolidation processes. The analytical solution follows the Dupuit-Forchheimer assumption and is verified through comparisons with numerical results. Sensitivity study reveals a potential increase in the mean travel time when the aquifer intersects with an impervious underground structure, while the degree of change depends on the interplay of two mechanisms (i.e., the increase in upgradient groundwater storage and the decrease in pore space of the consolidated zone). Global sensitivity analysis suggests that urban groundwater TTD systems are strongly dependent on both construction-related parameters and aquifer compressibility, indicating that adaptive strategies of groundwater management should be taken for different aquifer types. The proposed analytical model has great implications for the management of water resources in urban areas, the utilization of urban groundwater for human consumption, and the quality of urban aquifers.

The significant increase in urbanization has resulted in greater use of the subsurface in urban planning and, therefore, increased interaction between groundwater and underground infrastructure. Numerical models are the primary tool adopted to manage the resulting problems; however, their construction is time- and cost-consuming. Groundwater-level time-series analysis can be a complementary method, as this data-driven approach does not require an extensive understanding of the geological and boundary conditions, even if providing insights into the hydrogeologic behaviour. Thus, a data-driven approach was adopted to analyse groundwater time-series of the shallow aquifer, occupied by several underground structures, beneath Milan city (Northern Italy). Statistical (Mann-Kendall and Sen’s slope estimator, autocorrelation and cross-correlation, hierarchical cluster analysis) and geospatial techniques were used to detect the potential variables influencing the groundwater levels of 95 monitoring wells, covering the period 2005–2019. A general rising trend of the water table was identified, with local hydrogeologic differences in the western and southernmost areas. Based on time-series analysis results, four management areas have been identified. These areas could act as future geographic units with specific groundwater management strategies. In particular, subsurface public car parks can be classified with respect to groundwater flooding as (1) not submerged, (2) possibly critical, or (3) submerged at different groundwater conditions. According to these outcomes, targeted guidelines for constructing new car parks have been elaborated for each management area. The methodology proved to be efficient in improving the urban conceptual model and helping stakeholders design the planned underground development, considering groundwater aspects.

Groundwater dependent mega-cities exert enormous pressure on the watersheds in which they are situated, creating a demand for complex hydrogeologic modeling and analysis that provides decision-makers with the information they need. However, uncertainties about the characterization of the subsurface, hydrologic fluxes, and other model input, along with assumptions made during the modeling process can create difficulties in developing the models and interpreting the results in a way that ensures sustainable and equitable regional aquifer management. This dissertation uses a multiobjective analysis approach to determine the performance of spatially distributed aquifer management alternatives for the case study of the Valley of Mexico, where the Mexico City Metropolitan Area is situated. First, a three-dimensional finite-difference groundwater model is developed alongside an initial set of managed aquifer recharge alternatives and planning objectives in Chapter 2. The management alternatives tested show spatially distinct reductions in drawdown over the historical period for equivalent changes in storage and that combining multiple alternatives results in a more than an additive risk of groundwater flooding. These results point to the importance of including planning objectives calculated over diverse spatial extents in capturing impacts to groundwater security in urban basins. To address the potential for endogenous uncertainties in models to influence decision-making, Chapter 3 carries out a global sensitivity analysis across model parameter values and subsets of well observations using the model and alternatives developed in Chapter 2. Error metrics generally used to calibrate groundwater models are found to be sensitive to distinct parameters from those to which management objectives are sensitive and the coupled effects of the endogenous uncertainties have amplifying effects on the ranking of management alternatives. Both of these findings highlight the importance

Groundwater dependent mega-cities exert enormous pressure on the watersheds in which they are situated, creating a demand for complex hydrogeologic modeling and analysis that provides decision-makers with the information they need. However, uncertainties about the characterization of the subsurface, hydrologic fluxes, and other model input, along with assumptions made during the modeling process can create difficulties in developing the models and interpreting the results in a way that ensures sustainable and equitable regional aquifer management. This dissertation uses a multiobjective analysis approach to determine the performance of spatially distributed aquifer management alternatives for the case study of the Valley of Mexico, where the Mexico City Metropolitan Area is situated. First, a three-dimensional finite-difference groundwater model is developed alongside an initial set of managed aquifer recharge alternatives and planning objectives in Chapter 2. The management alternatives tested show spatially distinct reductions in drawdown over the historical period for equivalent changes in storage and that combining multiple alternatives results in a more than an additive risk of groundwater flooding. These results point to the importance of including planning objectives calculated over diverse spatial extents in capturing impacts to groundwater security in urban basins. To address the potential for endogenous uncertainties in models to influence decision-making, Chapter 3 carries out a global sensitivity analysis across model parameter values and subsets of well observations using the model and alternatives developed in Chapter 2. Error metrics generally used to calibrate groundwater models are found to be sensitive to distinct parameters from those to which management objectives are sensitive and the coupled effects of the endogenous uncertainties have amplifying effects on the ranking of management alternatives. Both of these findings highlight the importance

The significant increase in urbanization has resulted in greater use of the subsurface in urban planning and, therefore, increased interaction between groundwater and underground infrastructure. Numerical models are the primary tool adopted to manage the resulting problems; however, their construction is time- and cost-consuming. Groundwater-level time-series analysis can be a complementary method, as this data-driven approach does not require an extensive understanding of the geological and boundary conditions, even if providing insights into the hydrogeologic behaviour. Thus, a data-driven approach was adopted to analyse groundwater time-series of the shallow aquifer, occupied by several underground structures, beneath Milan city (Northern Italy). Statistical (Mann-Kendall and Sen’s slope estimator, autocorrelation and cross-correlation, hierarchical cluster analysis) and geospatial techniques were used to detect the potential variables influencing the groundwater levels of 95 monitoring wells, covering the period 2005–2019. A general rising trend of the water table was identified, with local hydrogeologic differences in the western and southernmost areas. Based on time-series analysis results, four management areas have been identified. These areas could act as future geographic units with specific groundwater management strategies. In particular, subsurface public car parks can be classified with respect to groundwater flooding as (1) not submerged, (2) possibly critical, or (3) submerged at different groundwater conditions. According to these outcomes, targeted guidelines for constructing new car parks have been elaborated for each management area. The methodology proved to be efficient in improving the urban conceptual model and helping stakeholders design the planned underground development, considering groundwater aspects.

Urban areas are major contributors to the alteration of the local atmospheric and groundwater environment. The impact of such changes on the groundwater thermal regime is documented worldwide by elevated groundwater temperature in city centers with respect to the surrounding rural areas. This study investigates the subsurface urban heat island (SUHI) in the aquifers beneath the Milan city area in northern Italy, and assesses the natural and anthropogenic controls on groundwater temperatures within the urban area by analyzing groundwater head and temperature records acquired in the 2016–2020 period. This analysis demonstrates the occurrence of a SUHI with up to 3 °C intensity and reveals a correlation between the density of building/subsurface infrastructures and the mean annual groundwater temperature. Vertical heat fluxes to the aquifer are strongly related to the depth of the groundwater and the density of surface structures and infrastructures. The heat accumulation in the subsurface is reflected by a constant groundwater warming trend between +0.1 and + 0.4 °C/year that leads to a gain of 25 MJ/m2 of thermal energy per year in the shallow aquifer inside the SUHI area. Future monitoring of groundwater temperatures, combined with numerical modeling of coupled groundwater flow and heat transport, will be essential to reveal what this trend is controlled by and to make predictions on the lateral and vertical extent of the groundwater SUHI in the study area.

The aim of this study is to investigate the occurrence of faecal indicator and microbial pathogens (bacteria and virus) in the shallow urban aquifer of the Besòs River Delta (NE Spain). To this end, human adenovirus (HAdV) and Norovirus of genogroups I and II (NoV GI and NoV GII) as well as the faecal indicator bacteria (FIB) Escherichia coli (EC) and faecal enterococci (FE) were monitored in groundwater and in the River Besòs in December 2013 and in July 2104. None of the targeted pathogens were detected in groundwater in December 2013 but contamination of human origin was observed in approximately 50% of the points sampled in July 2014 reaching concentrations up to 99 GC/100 mL for HAdV. Generally, microbial concentrations in river water were higher than those detected in groundwater. This observation indicates that pathogens are naturally attenuated when river water infiltrates and flows through the aquifer, however HAdV were detected at a sampling point located at 380 m from the river in the absence of FIB. The presence of human viral contamination may represent a risk for the use of groundwater as a drinking water source. Further research is needed to understand the dynamics of pathogens in river–groundwater interface over long time periods and a wide range of flow conditions (wet and dry periods) since the urban groundwater of this aquifer might be a valuable drinking water resource in Barcelona especially during drought periods. The methodology followed in this research can be applied to other urban aquifers with similar purposes since the scarcity and contamination of freshwater resources are worldwide issues.

The aim of this study is to investigate the occurrence of faecal indicator and microbial pathogens (bacteria and virus) in the shallow urban aquifer of the Besòs River Delta (NE Spain). To this end, human adenovirus (HAdV) and Norovirus of genogroups I and II (NoV GI and NoV GII) as well as the faecal indicator bacteria (FIB) Escherichia coli (EC) and faecal enterococci (FE) were monitored in groundwater and in the River Besòs in December 2013 and in July 2104. None of the targeted pathogens were detected in groundwater in December 2013 but contamination of human origin was observed in approximately 50% of the points sampled in July 2014 reaching concentrations up to 99 GC/100 mL for HAdV. Generally, microbial concentrations in river water were higher than those detected in groundwater. This observation indicates that pathogens are naturally attenuated when river water infiltrates and flows through the aquifer, however HAdV were detected at a sampling point located at 380 m from the river in the absence of FIB. The presence of human viral contamination may represent a risk for the use of groundwater as a drinking water source. Further research is needed to understand the dynamics of pathogens in river–groundwater interface over long time periods and a wide range of flow conditions (wet and dry periods) since the urban groundwater of this aquifer might be a valuable drinking water resource in Barcelona especially during drought periods. The methodology followed in this research can be applied to other urban aquifers with similar purposes since the scarcity and contamination of freshwater resources are worldwide issues. © 2019 Elsevier B.V.

Leaky water supply and sewer mains can become unmanaged sources of urban groundwater recharge and contamination posing environmental and health risks. Stable isotopes of water and hydrochemical tracer were applied to quantify water and sewage leakages in a shallow aquifer of a large Ukrainian city. Binary and ternary mixing models were used based on the d-excess and chloride concentrations of tap water, rural and urban groundwater to estimate fractions of natural recharge, urban seepage, volumes of water supply and sewage leakages in urban springs. Water supply leakages that recharge aquifer were ~ 3% (6.5 Mm3 a− 1) of the total water supply and strongly correlated with failures on the water infrastructure. Sewage leakages (1.4 Mm3 a− 1) to the aquifer were less in amount than water supply leakages, but induced nitrate and associated contaminants pollution risk of urban groundwater. The proposed method is useful for the pilot evaluation of urban groundwater recharge and contamination and can be applied in other regions worldwide to support the decision-making in water management.

Low groundwater levels could have negative consequences in urban areas, such as wooden pile degradation and accelerated land subsidence. Controlling groundwater levels by infiltration systems that recharge the groundwater could be important to prevent these problems. This research evaluates the technical effectiveness of different groundwater recharge systems in Dordrecht, aimed at increasing the phreatic groundwater levels near wooden foundation piles., Water Resources, Water Management, Civil Engineering and Geosciences

A tunnel for the High Speed Train (HST) was constructed in Barcelona with an Earth Pressure Balance (EPB) Tunnel Boring Machine (TBM). The tunnel crosses Barcelona and passes under some famous landmarks such as the Sagrada Familia and the Casa Mill Both monuments are UNESCO world heritage sites and a committee appointed by the UNESCO acted as external observers during the construction. Concerns about soil settlements and the hydrogeological impacts of the construction were raised. These concerns were addressed during the design stage to forestall any unexpected events. The methodology consisted of 1) characterising the geology in detail, 2) predicting the impacts caused in the aquifer, 3) predicting the soil displacements due to water table oscillations produced by the construction, and 4) monitoring the evolution of groundwater and soil settlements. The main estimated impact on groundwater was a moderate barrier effect. The barrier effect, the magnitude of which matched the predictions, was detected during construction. The monitoring of soil settlements revealed short and long term movements. The latter movements matched the analytical predictions of soil displacements caused by the groundwater oscillations. This paper proposes a realistic procedure to estimate impacts on groundwater during tunnel construction with an EPB. Our methodology will considerably improve the construction of tunnels in urban areas. (C) 2015 Elsevier B.V. All rights reserved., Peer Reviewed, Postprint (author's final draft)

Low groundwater levels could have negative consequences in urban areas, such as wooden pile degradation and accelerated land subsidence. Controlling groundwater levels by infiltration systems that recharge the groundwater could be important to prevent these problems. This research evaluates the technical effectiveness of different groundwater recharge systems in Dordrecht, aimed at increasing the phreatic groundwater levels near wooden foundation piles., Water Resources, Water Management, Civil Engineering and Geosciences

The occurrence and fate of UV filters (UV F) in an urban aquifer in correlation with (1) the spatial distribution of UV Fin Barcelona's groundwater, (2) the depth of the groundwater sample, (3) the physicochemical properties of the target compounds, (4) the recharge sources, and (5) the redox conditions of the Barcelona aquifers, were studied for the first time. The highest groundwater concentrations and the largest number of detected UV F were observed in an aquifer recharged by a polluted river (around 55 ng/L in SAP-4). In contrast, the urbanized areas had lower concentrations (around 20 ng/L in MPSP-1). Two pathways can be identified for UV F to enter the aquifers: (1) leakage of row sewage from the sewage network in urbanized areas and (2) wastewater treatment plant (WWTP) effluents discharged into the river. Measured concentrations of UV F were significantly much lower than those estimated from the waste water proportion in groundwater samples suggesting that UV F might undergo transformation processes in both reducing and oxidizing conditions. (c) 2014 Elsevier B.V. All rights reserved., Peer Reviewed, Postprint (published version)

Urbanization significantly affects water cycle on a local scale by both: altering the elements of the cycle and introducing new elements (such as water supply network or infiltration systems) and interactions with those elements. The new elements and interactions increase the complexity of water cycle modelling in urban settings. To achieve the goal of integrated urban water management, an integrated modelling of water cycle components has to be performed. 3DNet-UGROW is a software tool which integrates modelling of surface water, urban water systems and groundwater, considering all the interactions among those components of the water cycle. 3DNet-UGROW contains three simulation models: RUNOFF, which enables delineation of the ground surface into subcatchments and calculation of surface water balance, UNSAT, which simulates motion of infiltrated water within the vadose zone, described by Richards equation, and GROW, which enables groundwater flow and pollution transport simulation. During the past few decades an increasing trend of groundwater levels in the urban aquifers has been detected. This increase can partly be attributed to leakage from water mains. In this paper, the effect of water supply network leakage on groundwater levels in the urban part of Pančevački Rit near Belgrade is examined using the 3DNet-UGROW hydroinformatic tool.

Urban areas are the focus of major ecological, social and economical activity. They are thus also prime locations of increasing conflict with regard to water use and water protection. As a direct and/or indirect consequence of urban land use and human activity, urban water systems are frequently polluted with organic contaminants including waste water-born xenobiotics such as pharmaceuticals, personal care products (collectively known as PPCPs) and endocrine-active substances. This study reviews new integrated methodologies including flux calculations as well as chemical investigations for determining the impact of human activities on urban water systems and on processes within the urban watershed. The use of indicator substances, representing different contaminant sources and pathways, integral pumping tests and mass balance approaches are suitable alternatives within these environments. The issues are explored using contaminant mass balance examples from Halle/Saale and Leipzig, Germany.

A model has been developed to predict the origin of uncontrolled water flows. For this purpose, we analysed a total of 52 elements using ICP techniques on 72 water samples in all: 40 of them from leaks in the drinking water supply network and the remaining 32 from groundwater outcrops. The study focused on the cases registered within the Alicante town limits (Spain). The use of multivariate statistical classification tools such as discriminant analysis made it possible not only to reduce the number of analytes, but also to design a predictive model capable of assigning the group to which a new sample belongs. The elements that comprise the model are B, Mn, Te, Ce, Re, Sr, Li and Tl. Given the concentration of each element in the sample, the model can assign its precedence with a total success rate higher than 94%.

A model has been developed to predict the origin of uncontrolled water flows. For this purpose, we analysed a total of 52 elements using ICP techniques on 72 water samples in all: 40 of them from leaks in the drinking water supply network and the remaining 32 from groundwater outcrops. The study focused on the cases registered within the Alicante town limits (Spain). The use of multivariate statistical classification tools such as discriminant analysis made it possible not only to reduce the number of analytes, but also to design a predictive model capable of assigning the group to which a new sample belongs. The elements that comprise the model are B, Mn, Te, Ce, Re, Sr, Li and Tl. Given the concentration of each element in the sample, the model can assign its precedence with a total success rate higher than 94%.

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Urban groundwater resources are a matter of growing concern. Surface sealing and the urban subsurface infrastructure, such as water mains and the sewage system, can influence groundwater quality and quantity. To this end, groundwater deterioration within an urban watershed was assessed. An extensive monitoring programme concerning groundwater quality was combined with a numerical 3-D groundwater flow model of the study site. Results of the quality assessment revealed a pronounced influence of urban land use on the groundwater concentrations of the inorganic contaminants nitrate and boron. Within the urbanized part of the study area groundwater recharge is high and characterized by a fast response to rainfall. Here, the high degree of surface sealing does not necessarily contribute to surface runoff and enables fast infiltration of rainwater togroundwater through cracks and joints. Annual water and contaminant flow from the study area were estimated using the numerical groundwater model.

Water was sampled from over 100 sources in Nepal’s Kathmandu Valley, including municipal taps, dug wells, shallow-aquifer tube wells, deep-aquifer tube wells, and dhunge dharas (or stone spouts, public water sources that capture groundwater or surface water). Information was gathered on user preference and site and well characteristics, and water was examined for indicators of contamination from sewage, agriculture, or industry. Most problematic were total coliform and Escherichia coli bacteria, which were present in 94 and 72% of all the water samples, respectively. Contamination by nitrate, ammonia and heavy metals was more limited; nitrate and ammonia exceeded Nepali guidelines in 11 and 45% of the samples, respectively. Arsenic and mercury exceeded WHO guidelines in 7 and 10% of the samples, respectively, but arsenic never exceeded the less strict Nepali guideline. Significant differences existed in contamination levels between types of sources; dug wells and dhunge dharas, being the shallowest, were the most contaminated by bacteria and nitrate; deep-aquifer tube wells were the most contaminated by arsenic. Whereas E. coli concentrations decreased with depth, iron and ammonia concentrations increased with depth. These relationships account for people choosing to drink water with higher levels of bacterial contamination based on its superior (non-metallic) taste and appearance.

In this study, we used isotopic (d18O, d2H, d34S-SO4) and chemical tracers (boron) to assess the sources and transport processes of the micropollutants carbamazepine, galaxolide, and bisphenol A in groundwater underlying the city of Halle (Saale), Germany. Their ubiquitous presence in urban groundwater results from a combination of local river water infiltration, sewer exfiltration, and urban stormwater recharge. Attenuation during transport with infiltrating river water increased from carbamazepine (0-60%) to galaxolide (60-80%) in accordance with their increasing sorption affinity and decreasing recalcitrance against biodegradation. Distinctly higher attenuation during transport was found for carbamazepine (85-100%) and galaxolide (95-100%) if micropollutants originated from sewer exfiltration. Most likely, this is related to higher contents of organic matter and higher transit times of the respective flow paths. Although attenuation undoubtedly also affects the transport of bisphenol A, quantification is limited due to additional contributions from the urban stormwater recharge. As a consequence, micropollutant loads in groundwater indicate that groundwater discharge may dominate the export of bisphenol A from urban areas.

Xenobiotika werden zunehmend als ökotoxikologisch relevant für die aquatische Umwelt und den Menschen angesehen. Das Verhalten und die Auswirkungen dieser Stoffe in der Umwelt sind bisher nur wenig umfassend untersucht worden und werden deshalb im Rahmen des Projektes WASSER Leipzig durch das UFZ in einem urban geprägten Einzugsgebiet bearbeitet. Dieser Artikel stellt erste Analysen des Grund- und Oberflächenwassers vor. Es wurden die Gehalte der Industriechemikalien Bisphenol A und t-Nonylphenol, der polyzyklischen Duftstoffe Galaxolid und Tonalid, des antiepileptischen Medikaments Carbamazepin sowie von Koffein bestimmt, die ein ubiquitäres Vorkommen zeigten. In den Vorflutern wurden mittlere Konzentrationen von bis zu einigen 100 ng/l gemessen, die auf den Einfluss geklärter aber auch ungeklärter Abwässer zurückgeführt werden können. Im Grundwasser zeigten sich bis auf Bisphenol A geringere Werte. Die Belastung des Grundwassers ist auf Abwasserleckagen aus der Kanalisation zurückzuführen. Mithilfe einer Faktorenanalyse der hydrochemischen Messwerte lassen sich die Xenobiotika hinsichtlich ihres hydrochemischen Verhaltens im Grundwasser differenzieren. Xenobiotics are increasingly being considered as ecotoxicologically relevant for the aquatic environment and human health. Their behaviour and the effects on the environment have not yet been comprehensively investigated and, therefore, are currently the subject of the project WASSER Leipzig initiated by the UFZ. The results of this article are based on groundwater and surface water analyses of a watershed within the town of Leipzig. Here the industrial chemicals bisphenol-A and t-nonylphenol, the polycyclic fragrances galaxolide and tonalide, the antiepileptic drug carbamacepine and caffeine where investigated. Xenobiotics showed ubiquitous occurrence in the rivers, which were contaminated from treated and untreated sewage, as well as in groundwater, contaminated by leaky sewers. Mean concentrations up to several h

Cuando se estudian las aguas subterráneas en zonas urbanas deben tenerse en cuenta una serie de cuestiones específicas. La urbanización del territorio afecta significativamente al ciclo del agua tanto en cantidad como en calidad, en particular a la parte relacionada con la recarga y descarga de los acuíferos. Además las aguas pueden afectar a las infraestructuras urbanas subterráneas como sótanos, parkings, túneles de Metro o ferrocarril, conducciones, etc. Por estos motivos el estudio de las aguas subterráneas en zonas urbanas emerge con fuerza dentro de la hidrogeología. Algunos de los temas específicos para su estudio son: 1) Variaciones del nivel freático causadas por cambios en los usos del suelo y del agua; 2) Contaminación de las aguas subterráneas por la presencia de focos contaminantes tanto puntuales como difusos; 3) Caracterización y cuantificación de los componentes del balance hidrogeológico; 4) especificidades en la modelación del flujo subterráneo y el transporte de contaminantes; y 5) Integración de los datos hidrogeológicos para su gestión. Algunos de estos temas se ilustran aquí sobre el ejemplo de la ciudad de Barcelona. En los últimos años, tanto desde el ámbito público como privado, se ha llevado a cabo un amplio estudio hidrogeológico de la ciudad. El ascenso del nivel freático se ha convertido en un serio problema para muchas estructuras subterráneas, principalmente parkings y la red del Metro. Este ascenso se ha debido básicamente a la disminución en la explotación de las aguas subterráneas por una reducción significativa del consumo de agua para usos industriales. Aquí se presenta una evaluación de los principales términos que afectan a la recarga cuyo resultado es la cuantificación del balance hidrogeológico en el periodo comprendido entre 1965 a 1995. Se ha cuantificado en unos 40 hm3/a la cantidad total de agua que debe bombearse de los acuíferos para mantener los niveles freáticos a las cotas actuales. Si se bombean cantidades menores lo, A number of specific issues must be considered when dealing with groundwater in urban areas. Urbanization significantly affects the natural water cycle, both in terms of quantity and quality. In particular, the main contributors to recharge and discharge clearly differ from those in natural systems. Moreover, water can affect underground city infrastructures, such as basements, public transport services (trains, subway, .), and conductions. As a result, urban groundwater is emerging as a distinct branch of hydrogeology. Topics that are specific to urban groundwater include: 1) Fluctuations in groundwater levels caused by changes in land and water uses; 2) Pollution problems caused by point or non-point sources in urban areas; 3) Characterization and quantification of the components contributing to groundwater balance; 4) Specific characteristics of groundwater flow and solute transport models in urban areas; and 5) Integration of data for sustainable urban water management. Some of these issues are illustrated here for the case of Barcelona, where both the public and the private sectors have carried out a comprehensive hydrogeological study during the last years. Rising of groundwater levels beneath the city of Barcelona has become a serious problem to urban structures, such as the subway and underground parking areas. This rise is mainly due to a decline in groundwater exploitation, following a reduction in high water-consuming industrial activity in the city. We present an evaluation of the main terms affecting recharge in the city. The outcome is a global groundwater balance for the period 1965-1995. It has been quantified that a total rate of 40 million m3 per year should be pumped from the aquifers underneath the city in order to keep to the present groundwater levels. A lesser amount would lead to a rise in levels, and to continuing problems. Possible uses for this additional water are suggested. This case can be considered an example of how urbanisation p, Postprint (published version)