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The overall objective of the project was the development of water management system solutions for a sustainable improvement of water quality in the city of Chaohu and in the Chao Lake. The Urban Water Resources Management (UWRM) concept is the innovative approach, which includes both efficient urban water management in urban and suburban areas, as well as interaction with aquatic ecosystems. Data and models for planning purposes and regional water management are made available by using a comprehensive online environmental information system for authorities and water suppliers. The Chao Lake plays a central role as an ecological and economic protection and raw water supplier for the drinking water supply of the population of the city of Chaohu. The research and development project (R&D Project) thus makes an important contribution to the sustainable development of the Chaohu region as part of the Masterplan Ecological Seascape Chaohu of the Anhui Provincial Government. The scientific and technical solutions are implemented in demonstration projects.

Environmental systems are complex. For unravelling this complexity both observation and modelling concepts are being developed and applied - still and mostly in independent ways. Developing and establishing continuous workflows in environmental systems analysis integrating observation as well as modelling aspects shall help overcoming this disparity. In this paper we present basic concepts of technical workflow development in geosciences and show examples from different applications in geotechnics. Technical workflows combine data integration, numerical simulation and data analysis and therefore support the modelling process. Benchmarking is an essential tool for proving complex workflows, e.g., the consistency between experimental work and process modelling.

Clay rock is being investigated in many countries as a potential host rock for nuclear waste repositories. Due to the state of over-consolidation and water saturation, characterisation of undisturbed rock with regard to its hydraulic and mechanical properties is a big challenge. Increased complexity is caused by temperature change in the repository of high-level waste. In situ measurement of single component, e.g. rock permeability, was conducted in the Mont Terri Rock Laboratory (CH) and the French Underground Research Laboratory Bure. Several so-called heater experiments are being carried out at different scale. The measured data including temperature, humidity, pore pressure, and deformation in various boreholes shows strong coupling effects. For interpretation of the experimental data, a numerical 3D code OpenGeoSys (OGS) was developed taking into account the strongly coupled thermal, hydraulic and mechanical processes. Because of the significant dependency of the thermal conductivity on the water saturation, the determination of the saturation state, which is again controlled by hydraulic permeability, is therefore important. The evaluated permeability from packer tests can be validated using numerical modelling. The state-dependency on the pressure, saturation and temperature is discussed.

With the rapid development of remote sensing, and earth observation technology, increasingly huge amount of geospatial data became available. These data enables the monitoring and evaluation of the environment and provides data source for numerous environment models, which in turn generate huge simulation results data. Utilization of both, remote sensing data and simulation results will be of great value for environmental related researchers, the public and local governments to support relevant research and environmental related decision- making processes. With these data, the government could establish the scientific rules for the exploitation and utilization of resources, to maintain the sustainable development of local economy and society. However, these data are heterogeneous and complex, exist in a variety of formats and is difficult to understand and analyze. Therefore, it is essential to build a system, which can integrate these data in a unified context, combine the relevant data sets, and present these data in an intuitive way.

The general goal for this initiative is to build a Sino-German research network by leading Chinese scientists with their research groups and German experts in the field of environmental informatics, hydrology, climatology and remote sensing (satellite born earth observation). This initiative will form the basis for intensive exchange of research methods and knowledge, and is intended to the development of bilateral research project proposals e.g. to the Ministry of Science and Technology of the People’s Republic of China (MOST), National Natural Science Foundation of China (NSFC), German Research Foundation (DFG), German Federal Ministry for Education and Research (BMBF) and/or European Commission (EC).

The Research Centre for Environmental Information Science (RCEIS) was established in March 2014. In the long-term vision RCEIS shall become a Sino-German competence centre and research platform for Earth systems observation and modelling by combining expertise in the fields of environmental and information sciences using modern information technology. As a scientific goal, RCEIS will develop novel concepts by using infrastructures for Earth system observation and analysis in order to better understand the evolution and dynamics of environmental systems under global change and globalization (anthropogenic pressure). An important methodology is the further development and combination of different infrastructures for Earth system observation, e.g. combining information from remote sensing (satellites and airborne) and “ground-truth” measurements. Moreover, monitoring (remote sensing and monitoring) and modelling platforms (multi-sphere/compartment, cycle-oriented) need to be combined.

Scientific visualization developed successful methods for scalar and vector fields. For tensor fields, however, effective, interactive visualizations are still missing despite progress over the last decades. We present a general approach for the generation of separating surfaces in symmetric, second-order, three-dimensional tensor fields. These surfaces are defined as fiber surfaces of the invariant space, i.e. as pre-images of surfaces in the range of a complete set of invariants. This approach leads to a generalization of the fiber surface algorithm by Klacansky et al. [16] to three dimensions in the range. This is due to the fact that the invariant space is three-dimensional for symmetric second-order tensors over a spatial domain. We present an algorithm for surface construction for simplicial grids in the domain and simplicial surfaces in the invariant space. We demonstrate our approach by applying it to stress fields from component design in mechanical engineering.

Groundwater travel time distributions (TTDs) provide a robust description of the subsurface mixing behavior and hydrological response of a subsurface system. Lagrangian particle tracking is often used to derive the groundwater TTDs. The reliability of this approach is subjected to the uncertainty of external forcings, internal hydraulic properties, and the interplay between them. Here, we evaluate the uncertainty of catchment groundwater TTDs in an agricultural catchment using a 3-D groundwater model with an overall focus on revealing the relationship between external forcing, internal hydraulic property, and TTD predictions. A stratigraphic aquifer model is applied to represent the spatial structure of the aquifer. Several recharge realizations are sampled from a high-resolution dataset of land surface fluxes and states. Constrained to expert knowledge and groundwater head observations, many realizations of hydraulic conductivity fields are stochastically generated using null-space Monte Carlo (NSMC) method for each recharge realization. The random walk particle tracking (RWPT) method is used to track the pathways of particles and compute travel times. Moreover, an analytical model under the random sampling (RS) assumption is fitted against the numerical solutions, serving as a reference of the mixing behavior of the model domain. The StorAge Selection (SAS) function is used to interpret the results in terms of quantifying the systematic preference for young/old water. The simulation results reveal the primary effect of recharge on the predicted mean travel time (MTT). The different realizations of calibration-constrained hydraulic conductivity fields moderately magnify or attenuate the predicted MTTs, provided that most parameters can be well constrained to the observations. The analytical solution under a random sampling assumption does not properly replicate the numerical solution, and underestimates the mean travel time. The SAS functions of ensemble simulations indicate an overall preference for young water for all realizations. The spatial pattern of recharge also has a strong impact on the shape and breadth of simulated TTDs. In conclusion, overlooking the input (forcing) uncertainty will result in biased travel time predictions, and may underestimate the overall uncertainty of TTD predictions. We also highlight the worth of reliable observations in reducing predictive uncertainty, and the good interpretability of SAS function in terms of understanding catchment transport processes.

DECOVALEX-2015 : an international collaboration for advancing the understanding and modeling of coupled thermo-hydro-mechanical-chemical (THMC) processes in geological systems

Microscale zero valent iron (mZVI) is a promising material for in-situ contaminated groundwater remediation. However, its usefulness has been usually inhibited by mZVI particles' low mobility in saturated porous media for sedimentation and deposition. In our study, laboratory experiments, including sedimentation studies, rheological measurements and transport tests, were conducted to investigate the feasibility of xanthan gum (XG) being used as a coating agent for mZVI particle stabilization. In addition, the effects of XG concentration, flow rate, grain diameter and water chemistry on XG-coated mZVI (XG-mZVI) particle mobility were explored by analyzing its breakthrough curves and retention profiles. It was demonstrated that XG worked efficiently to enhance the suspension stability and mobility of mZVI particles through the porous media as a shear thinning fluid, especially at a higher concentration level (3 g/L). The results of the column study showed that the mobility of XG-mZVI particles increased with an increasing flow rate and larger grain diameter. At the highest flow rate (2.30 × 10 −3 m/s) within the coarsest porous media (0.8–1.2 mm), 86.52% of the XG-mZVI flowed through the column. At the lowest flow rate (0.97 × 10 −4 m/s) within the finest porous media (0.3–0.6 mm), the retention was dramatically strengthened, with only 48.22% of the particles flowing through the column. The XG-mZVI particles appeared to be easily trapped at the beginning of the column especially at a low flow rate. In terms of two representative water chemistry parameters (ion strength and pH value), no significant influence on XG-mZVI particle mobility was observed. The experimental results suggested that straining was the primary mechanism of XG-mZVI retention under saturated condition. Given the above results, the specific site-related conditions should be taken into consideration for the design of a successful delivery system to achieve a compromise between maximizing the radius of influence of the injection and minimizing the injection pressure.

Summary Ground water flow systems of shallow sedimentary basins are studied in general by analyzing the fluid dynamics at the real world example of the Thuringian Basin. The impact of the permeability distribution and density differences on the flow velocity pattern, the salt concentration, and the temperature distribution is quantified by means of transient coupled simulations of fluid flow, heat, and mass transport processes. Simulations are performed with different permeabilities in the sedimentary layering and heterogeneous permeability distributions as well as with a non-constant fluid density. Three characteristic numbers are useful to describe the effects of permeability on the development of flow systems and subsurface transport: the relation of permeability between aquiclude and aquifer, the variance, and the correlation length of the log-normal permeability distribution. Density dependent flow due to temperature or concentration gradients is of minor importance for the distribution of the flow systems, but can lead to increased mixing dissolution of salt. Thermal convection is in general not present. The dominant driver of groundwater flow is the topography in combination with the permeability distribution. The results obtained for the Thuringian Basin give general insights into the dynamics of a small sedimentary basin due to the representative character of the basin structure as well as the transferability of the settings to other small sedimentary basins.

In a common, designed disposal system for high-level radioactive waste, bentonite is used worldwide as a buffer material due to its favorable thermodynamic properties. In-situ experiments at different scales are being conducted in several underground laboratories to investigate the long-term coupled thermo-hydro-mechanical (THM) and chemical behavior of bentonite. Simultaneously, numerous laboratory experiments under well-defined conditions were performed to determine the material properties of bentonite. Since 2012, a laboratory heating and hydration test on MX-80 bentonite has been performed by CIEMAT ( Centro de Investigaciones Energeticas , Medioambientales y Tecnologicas ). The obtained data during the test were analyzed by different research teams within the international DECOVALEX project in order to understand the coupled THM behavior of bentonite and furthermore to determine the thermal-mechanical properties of bentonite. This paper presents a numerical model for fully-coupled THM processes in bentonite based on the finite element method program OpenGeoSys (Kolditz et al., 2012a). In this model, the description of heat conduction is based on Fourier's law, and advection is also considered in the heat transfer. As an important coupling factor from hydraulic process to thermal process, the dependency of thermal conductivity on the water saturation is intensively analyzed. A multiphase flow model considering water evaporation and vapor diffusion is used to describe the hydraulic process. Special attention was also paid on the analysis of the water retention behavior. An elastic constitutive model based on generalized Hook's law was applied to describe the material's mechanical behavior complemented with consideration of the thermally induced strain and the swelling deformation. Good agreement between the calculated and measured data has been achieved concerning temperature, relative humidity, total stress, and water intake. The main coupling processes and bentonite behavior in the experiment could be captured and well analyzed in this model. However, further investigations are also needed, especially for the long-term THM process with respect to water intake.

It has been over 15 years since the concept of Virtual Geographic Environments (VGEs) was formally proposed (Lin and Gong 2001). Although the thinking about VGEs never stops since it was born, and the continued development of VGEs has brought about significant achievements resulting from this concept (e.g., Goodchild 2009; Gong et al. 2010; Konecny 2011; Lu 2011; Priestnall et al. 2012; Lin et al. 2013a, b, 2015) as well as related technologies and implementations (e.g., Xu et al. 2011, 2013; Chen et al. 2012, 2013a, b; Zhang et al. 2015a, b; Zhu et al. 2015), there are still some misunderstandings about this ‘new’ branch of Geoscience. Questions generally are related to two concepts: the first concerns the differences between VGEs and game-like virtual worlds, similar virtual communities and cities, and digital earth; the second asks how VGEs can contribute to geographic research beyond traditional Geographic Information Systems (GIS) and Maps (Aydi et al. 2013; Tung et al. 2013). The answer to the first question may be found in the term ‘geographic environment’ which refers not only to the natural surface of the earth, space, or a place, but also involves the social behaviors that interact with natural factors; it is the sphere of direct interaction between nature and society (Kalesnik 1979). An important feature of geographic environments is that they change continuously with time. Although some objects in geographic environments have relatively stable shapes (such as a rock or soils), many exist in constantly changing forms (such as vegetation, air and water), and human beings (both in groups or individual) are active throughout their ‘lives’. Given this definition, to build a virtual mirror that can reflect the real geographic environment, only considering the physical part would result only in a one-sided perspective. Moreover, dynamic geographic phenomena and processes require careful attention, a fact often overlooked by traditional systems. Thus, an ideal virtual environment

Combining and solving environment and health is a major issue in China—a country with tremendous economic development perspectives. Recent developments (e.g., the Tianjin Harbor accident in August 2015) show that China is investing more and more resources and efforts to cope with the industrial development (GDP) into alliancing with environmental safeguarding. The Thematic Issue on Environment and Health in China is a starting point for discussion of a variety of environmental issues, such as distribution and fractionation of rare earth elements in soil–water system and human blood (Li et al. 2014a, b, c, d); spatial evaluation of phosphorus retention in riparian zones using remote sensing data concerning the big and scarce data issues (Dong et al. 2014); toxicity contamination and distribution in soils and plants (Li et al. 2014a, b, c, d); the status and challenges of water pollution problems in China: learning from the European experience (Zhou et al. 2014); the Heihe River basin (Xiao et al. 2014), identifying interactions between river water and groundwater in the North China Plain using multiple tracers (Dun et al. 2014); potential hazardous elements (PHEs) in atmospheric particulate matter (APM) in the south of Xi’an during the dust episodes of (2001–2012) chemical fractionation; ecological and health risk assessment (Li et al. 2014a, b, c, d), occurrence and hydrogeochemistry of fluoride in alluvial aquifer of Weihe River (Li et al. 2014a, b, c, d); contamination assessment and health risk of heavy metals in dust from Changqing industrial park of Baoji (Wang et al. 2014a, b); contamination assessment and health risk of heavy metals in dust from Changqing industrial park of Baoji (Su et al. 2014); sources and transports of polycyclic aromatic hydrocarbons in the Nanshan Underground River, China (Alam et al. 2014); introducing a land-use-based spatial analysis method for human health risk evaluation of soil heavy metals (Wang et al. 2013a, b, c)

This paper presents the design and integration of a GIS-based data model for the regional hydrologic simulation in the Meijiang watershed, China. Hydrologic systems (HS) require integration of data and models simulating different processes. Here, an object-oriented approach using Unified Modeling Language (UML) is introduced, which supports the development of GIS-based Geodatabase model—GeoHydro/DataBase (GH/DB). Spatial data, such as basins, stream network, and observation stations are stored in the feature classes. The time series and their attributes are included in the tables. Relationship classes are used to link associated objects. The new development within the scientific program OpenGeoSys (OGS) is the integration of GH/DB into the numerical simulations. The graphical user interface is implemented for the pre- and post-processing of the simulation. As for the case study, a regional hydrologic model is developed in the Meijiang watershed area for the understanding of water infiltration from surface into groundwater via soil layer with various time scales. The integration of databases and modeling tool represents the comprehensive hydrosystems and thus it is a useful tool to understand the different processes and interactions between the related hydrological compartments.

Quality of surface waters is a severe problem worldwide (Dimberg and Bryhn 2014; Harmon et al. 2014; Christia et al. 2014; Renjith et al. 2013; Sedlacek et al. 2013; Antunes et al. 2013; Rinke et al. 2013; Watchorn et al. 2013; George et al. 2013) but particularly important to China because of the water resources use from the huge rivers originating in the Tibetan plateau flowing through the North China Plain into the Pacific Ocean. The water quality issue includes nutrients (Ji et al. 2014; Wu et al. 2013), in particular phosphorus (Chen and Zhao 2014; Chen et al. 2014; Yuan et al. 2014; Zhu et al. 2013; Liu and Chang 2013) and many other pollutants. To develop solutions for a sustainable water resources management, in addition to technological solutions also socio-economic studies are important to conduct for governance, regulation and acceptance issues (Antonellini et al. 2014; Kerschbaumer et al. 2015; Subagadis et al. 2014; Wang et al. 2014) as well as organic pollutants (Tilman et al. 2013) and microbiological hazards (Stoll et al. 2012; Xueping et al. 2014). Recent Thematic Issues in EES were dealing with Integrated Water Resources Management under different hydrological, climatic and socio-economic conditions (Kalbus et al. 2012; Grathwohl et al. 2013; Seegert et al. 2014) including topics like progress in monitoring and modeling concepts (Beinhorn et al. 2005; Beyer et al. 2006; Kalbacher et al. 2012; Rink et al. 2012). The protection of aquatic ecosystems and the security of drinking water provision are becoming an increasing economic challenge in water management. The Chinese government recognizes the importance and complexity of the situation and has initiated a program titled ‘‘Major Water Program of Science and Technology for Water Pollution and Governance’’ (2006–2020). A series of EES Thematic Issues are

The study of water sorption in microporous materials is of increasing interest, particularly in the context of heat storage applications. The potential-theory of micropore volume filling pioneered by Polanyi and Dubinin is a very useful tool for the description of adsorption equilibria. Based on one single characteristic curve, the system can be extensively characterised in terms of isotherms, isobars, isosteres, enthalpies etc. However, the mathematical description of the adsorbate density's temperature dependence has a significant impact especially on the estimation of the energetically relevant adsorption enthalpies. Here, we evaluate and compare different models existing in the literature and elucidate those leading to realistic predictions of adsorption enthalpies. This is an important prerequisite for accurate simulations of heat and mass transport ranging from the laboratory scale right up to the reactor level of the heat store.

Thermal energy storage technologies are of current interest in order to improve the integration of renewable energy sources as well as energy efficiency. Numerical simulations of thermochemical heat storage are especially challenging and time consuming due to the complexity of the mathematical description of the strongly coupled and highly nonlinear processes characteristic for such systems. These difficulties are exacerbated once practically relevant complex or large geometries are considered as they can occur around heat exchangers or due to internal heterogeneities of the reactive bed. To allow a computationally efficient simulation of such applications, an existing finite element implementation of a thermochemical heat storage model was parallelised using PETSc routines. Input/output, global assembly and the linear solver all work in a distributed fashion. The approach is implemented into the open source framework OpenGeoSys. The performance of the present parallelisation approach is tested by simulating the discharge of a heat store based on calcium-oxide and water as a benchmark problem. The computational time required for the simulation could be reduced significantly.

This work reports numerical stability conditions in two-dimensional solute transport simulations including discrete fractures surrounded by an impermeable rock matrix. We use an advective-dispersive problem described in Tang et al. (1981) and examine the stability of the Crank-Nicolson Galerkin finite element method (CN-GFEM). The stability conditions are analyzed in terms of the spatial discretization length perpendicular to the fracture, the flow velocity, the diffusion coefficient, the matrix porosity, the fracture aperture, and the fracture longitudinal dispersivity. In addition, we verify applicability of the recently developed finite element method-flux corrected transport (FEM-FCT) method by Kuzmin (2009) to suppress oscillations in the hybrid system, with a comparison to the commonly utilized Streamline Upwinding/Petrov-Galerkin (SUPG) method. Major findings of this study are (1) the mesh von Neumann number (Fo) ≥ 0.373 must be satisfied to avoid undershooting in the matrix, (2) in addition to an upper bound, the Courant number also has a lower bound in the fracture in cases of low dispersivity, and (3) the FEM-FCT method can effectively suppress the oscillations in both the fracture and the matrix. The results imply that, in cases of low dispersivity, prerefinement of a numerical mesh is not sufficient to avoid the instability in the hybrid system if a problem involves evolutionary flow fields and dynamic material parameters. Applying the FEM-FCT method to such problems is recommended if negative concentrations cannot be tolerated and computing time is not a strong issue.

Xanthan gum-coated microscale zero valent iron (XG-mZVI) is potentially an inexpensive and effective material to promote the degradation of environmental contaminants. The effects of geochemical constituents (humic acid (HA), Ca 2 + / Mg 2 + - HCO 3 - , Na + - Cl - ) on trichloroethylene (TCE) removal using XG-mZVI were investigated using batch experiments to evaluate the potential performance of XG-mZVI in field treatments. TCE was removed from groundwater by adsorption and chemical reduction. In the co-presence of geochemical constituents, TCE adsorption was not significantly impacted, while its reduction rate was increased by the presence of HA (5–20 mg L−1), inhibited with increasing Ca(HCO3)2 and Mg(HCO3)2 concentrations (0.4–2 mM) and unaffected by NaCl in the range of 10–100 mM. The promotional effect of HA on TCE reduction was primarily due to the Fe-humate complexes in solution that delayed the formation of passivated precipitates. However, the presence of Ca(HCO3)2 and Mg(HCO3)2 exerted an opposite effect on TCE reduction by facilitating the formation of passivated precipitates, such as green iron rust. These findings provide insight into the impact mechanism of XG-mZVI reactivity by organic and inorganic geochemical constituents with particular implications for the XG-mZVI degradation of TCE in real groundwater.

The Thematic Issue is dedicated to different aspects of using the potential of the geologic subsurface as a resource for energy production (e.g., hydrothermal and petrothermal resources), energy storage as well as for safe deposition of energy waste, and energy conversion (e.g., as biochemical reactors to convert hydrogen and carbon dioxide into methane). Figure 1 shows an overview map of hydrothermal systems in China including a classification to high-, midand low-temperature reservoirs and basins (Kong et al. 2014). Current research efforts concerning hydrothermal resources focus on the sustainable development of large-scale geothermal fields. Pang et al. (2012) designed a roadmap of geothermal energy development in China and reported the recent progress in geothermal research in China (Pang et al. 2014). Recently, Pang et al. (2015) presented a new classification of geothermal resources based on the type of heat source and followed by the mechanisms of heat transfer. The present Thematic Issue is focusing on petrothermal resources and particularly enhanced geothermal systems. Some of the basins indicated in Fig. 1 are also of interest for unconventional gas resources which is discussed in a separate Thematic Issue in Environmental Earth Sciences (Hou et al. 2015a). Geothermal energy resources are considered to provide a significant contribution to renewable energy supply from both shallow and deep systems (Arola et al. 2014; Huenges et al. 2013; Kolditz et al. 2013; Scheck-Wenderoth et al. 2013). Understanding the thermally induced coupled processes is important for reservoir operations (McDermott et al. 2006; Kolditz and Diersch 1993). Breede et al. (2014) provide a systematic review of enhanced or engineered geothermal systems (EGS). Ramos et al. (2015) provide a systematic review of projects implemented worldwide and a methodology for screening geothermal projects. Geothermal shallow surface systems based on ground source heat pumps have already proved to be a feasible option for the heating and cooling of buildings. The present work studies the concept of using abandoned mines for geothermal heat recovery in various countries such as Germany, the Netherlands, Norway, Russia, Spain, UK and United States. De Filippis et al. (2015) are discussing the geothermal potential of the Salento peninsula in southern Italy. They propose a simple methodology for the assessment of low-enthalpy geothermal energy systems based on stochastic approaches. They found that coastal areas might lower potential due to saltwater intrusion problems. Hou et al. (2015b) introduce the first & Hongwei Zhou zhw@cumtb.edu.cn

Coalbed methane, tight and shale gas are three important unconventional gas resources in China. ‘‘According to data from the Ministry of Land and Resources, at the end of 2013, China had 11, 12 and 25 trillion cubic meters, respectively of remaining technically recoverable resources of coalbed methane, tight gas and shale gas which are still in the early stage of development’’. (Source CNPC and ARA International Limited). China is developing its shale gas exploration and exploitation strategies for economic reasons and social aspects (so-called ‘‘shale gas revolution’’). Huge shale gas reserves provide a reliable source for sustaining China’s economic development and contributing to China’s ‘‘Energiewende’’. Zhao et al. (2015a) analyze the strategic measures and advantages for a safe and vigorous development of shale gas in China and review the developments of hydraulic fracturing technologies in China. Economic exploitation for shale gas is highly dependent on the complexity of the fracture network caused by hydraulic fracturing technology, so it is necessary to accurately assess the effect of the fracture network on gas flow behavior and productivity (Li et al. 2015c). This thematic issue is particularly dedicated to recent researches in unconventional gas resources in China related to the reservoirs indicated in Fig. 1 in order to substitute coal by ‘‘clean’’ gas energy resources as a transitional technology towards renewable energy resources. The thematic issue compiles theoretical, experimental as well as field studies in China. Different reservoir types are under investigation such as tight and shale gas reservoirs as well as coal mines with coalbed methane resources. Fundamental aspects on process understanding in unconventional gas reservoirs as well as the international context of research and technology deployment are discussed in this volume. Tight gas reservoirs have become an important resource for the world’s gas supply. Such reservoirs have very low permeability (usually below 0.1 mD) and show a strong stress sensitivity to fluid transport properties and a considerable productivity decline during the production process due to decreasing reservoir pressure as well as increasing effective stress. In an experimental study by Albrecht and Reitenbach (2015) several measurement series were performed on plugs from the North-German Rotliegend tight gas reservoirs to determine the effects of changing stress and pore pressure conditions on reservoir & Olaf Kolditz olaf.kolditz@ufz.de

Rapid economic development and population growth inChina go hand-in-hand with increasing urbanisation, in-volving growing mega-cities, industrialization, and inten-sified agriculture. As a result, natural resources areincreasingly stressed and productive management strate-gies towards sustainable planning are urgently needed.Pollution containing hazardous substances for environ-mental and human health, depletion of water resources as aresult of overexploitation, soil degradation and air pollutionin mega-cities (such as Beijing or Shanghai) are increasingat an alarming rate. Consequently, the protection of aquaticecosystems and the security of drinking water provision arebecoming an increasing challenge in water management.The Chinese government recognized the importance andcomplexity of the situation and has initiated a programentitled ‘‘Major Program of Science and Technology forWater Pollution and Governance’’ (2006–2020) (MajorWater Program). While shortages resulting from regionalresource depletion have led to plans for large-scale watertransport from distant water-rich areas of China (WaterDiversion Project), the water quality problems in otherareas require efficient, flexible, and site-specific solutionsand overall management concepts. China is internationallycooperating with many countries to tackle the severeenvironmental problems and learning from their experi-ences. In particular, China can benefit from the lessonslearnt in Germany concerning the rehabilitation of waterresources in areas heavily affected by chemical industryand mining after the reunification in 1989. German–Chi-nese cooperation in water sciences started over 25 yearsago and is dealing now with increasing challenges in the21st century (Chen et al. 2015). Under the umbrella of‘‘International Partnerships for Sustainable Technologiesand Services for Climate Protection and the Environment’’(CLIENT) under the ‘‘Research for Sustainable Develop-ment’’ framework programme the Federal Ministry ofEducation and Research of Germany (BMBF) started aseries of research projects supporting the Chinese MajorWater Program in several regions, the lakes, Taihu, Chaohuand Dianchi, as well as the Liao River Basin (Fig. 1).The Liao River Basin is located in northeast China withtwo river systems, one system is the Liao River formed byconverging Xiliao River and Dongliao River, and the othersystem is the Daliao River formed by converging HunRiver and Taizi River (Fig. 1). The province of Liaoningderived its name from the river. Shenyang is the provincialcapital of Liaoning. Liaoning was one of the first provincesin China to industrialize and heavy industry led to severeenvironmental pollution including the water environment.Liaoning has the largest economy of Northeast Chinacovering a wide range of industries, such as metallurgy,petroleum, chemical industries, pulp and paper making,pharmaceutical industry, printing and dyeing, machinery,electronics, metal refining, construction materials, ore andcoal mining, etc. The Liaohe-Songhuajiang River Basinbelongs to the priority areas of the Chinese Major WaterProgram. The Chinese central government launched a‘‘Revitalizing Northeast China and Other Old IndustrialBases’’ campaign (2005, http://www.china.org.cn/e-news/

International audience; For the deep geological disposal of high-level radioactive waste in argillaceous rocks, the heat production of the waste is an important driver for thermal–hydraulic-mechanical (THM)-coupled processes. These THM processes influence the properties and conditions of the near field that in many repository designs contains bentonite as a clay buffer. One task in the DECOVALEX-2015 (DEvelopment of COupled models and their VALidation against Experiments) project was the modelling of a heated bentonite column (Villar et al. in Long-term THM tests reports THM cells for the HE-E test update of results until February 2014. Deliverable-no D2.2-7.3. CIEMAT Technical Report IEMAT/DMA/2G210/03/2014, 2014) in preparation for the in situ heater experiment HE-E at the underground rock laboratory Mont Terri. DECOVALEX is an international cooperative project that focuses on the development and validation of mathematical models for simulating such coupled processes associated with disposal in deep geological repositories. Eight modelling teams developed their own THM-coupled models for the bentonite column experiment, using six different simulation codes. Each of the teams individually calibrated the THM parameters for the bentonite material. The eight resulting parameter sets agree well and allow a satisfactory reproduction of the TH measurements by all models. The modelling results for the evolution of temperature and relative humidity over time at three sensors in the bentonite column are in good agreement between the teams and with the measured data. Also, changes of the temperature due to modifications of the insulation and the adjustment of the heating power during the course of the experiment are well reproduced. The models were thus able to reproduce the main physical processes of the experiment, both for vapour-dominated diffusion during the heating phase and combined liquid and vapour transport during a subsequent heating and hydration phase. Based on the parameter sets, the teams predict a penetration of the water infiltration front in the 48-cm column filled with bentonite pellets to a depth between 25 and 35 cm over the 15,000 h (i.e. over 20 months) of the hydration phase of the experiment. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.

Failure in brittle rock happens because micro-cracks in the crystal structure coalesce and form a localized fracture. The propagation of the fracture is in turn strongly influenced by dissipation in the fracture process zone. The classical theory of linear elastic fracture mechanics falls short in describing failure when the dissipation in the fracture process zone is non-negligible; thus, a non-linear theory should be employed instead. Here we present a study in which we explore the characteristics of the fracture process zone in granite. We have combined fracture tests on Adelaide black granite with acoustic emission detection and finite element analyses by using a non-local integral plastic-damage constitutive theory. We have further employed the theory of configurational mechanics to support our interpretation of the evolution of the fracture process zone with strong energy-based arguments. We demonstrate that the size of the fracture process zone is non-negligible and dissipative phenomena related to micro-cracking play an important role. Our results indicate this role should be assessed case by case, especially in laboratory-sized analyses, which mostly deflect from theories of both size-independent plasticity and linear elastic fracture mechanics. When strong non-linearities occur, we show that fracture energy can be correctly computed with the help of configurational mechanics and that complex numerical simulation techniques can substantially facilitate the interpretation of experiments designed to highlight the dominant physical mechanisms driving fracture.

OpenGeoSys (OGS) together with its predecessors looks back at a long history as a simulation code of coupled thermal, hydraulic, mechanical and chemical (THMC) phenomena in fractured porous media: starting as the Fortran code Rockflow in the 1986, ranging over a C implementation and now using different flavours of the C++ programming language; in the meantime undergoing two renames, namely to GeoSys and now OpenGeoSys.

This deliverable reports the establishment of index system for groundwater source risk assessment in the SUSTAIN H2O project during the project’s 1st reporting period. Two demonstration areas in the SLRB were chosen: one in Ashi River Basin and the other in Taizi River Basin. Ashi River is a tributary of Songhua River and Taizi River is a tributary of Liao River. The consortium members have conducted several field surveys in the study areas and acquired first-hand information. Experts from Germany provided technologies and strategies on groundwater risk assessment in EU countries. This deliverable is the outcome of the internal and external collaborations that the consortium members have engaged in the context of the SUSTAIN H\({}_{2}\)O project.

In this chapter, the first real-world scenario is simulated using the model developed in Chap. 2.

In this chapter a mathematical model for a fixed bed of adsorbent pellets in an open-mode heat storage device is derived. At first a the general modelling workflow is presented. Afterwards the governing equations of the system are derived from the physical balance laws in combination with constitutive relations for material properties. Special focus is laid on the constitutive relations for the sorption equilibrium and kinetics.

In the framework of the EU-China Environmental Sustainability Program, the SUSTAIN H2O project was launched in 2013 and ran over 36 months until 2016. Sustain H2O is an abbreviation which stands for “Demonstration of Pollution Discharge Management for Water Quality Improvement in the Songhuajiang-Liaohe River Basin (SLRB)”. The SLRB represents China’s old industrial base with a large number of water-polluting industries. It has been selected as it is a key river basin for water pollution control and water environment management with clearly defined challenges in terms of pollution emission reduction and water quality improvement. Some of these challenges/problems include excessive discharge of pollutants, no optimal load allocation mechanism of quantity control, poor water quality and severely damaged water ecology as well as high risk of environmental pollution accidental events that threaten the safety of drinking water sources. Moreover, the SLRB is a trans-national (transboundary) river catchment, flowing from China to Russia, and therefore is well suited as a joint Sino-EU action.

High-level radioactive waste (HLW) and spent fuel from nuclear power plants (SF) require very long duration disposal because of its long-lived toxicity. Specific repository design is necessary to accommodate the associated large heat generation from continual decay. Conceptual designs propose geological containment within salt, claystone, or crystalline bedrock. However, while many studies have investigated the safety of disposal in these host rocks, the interaction of near-field heat coupled to far-field groundwater flow for UK-relevant conditions has not been fully investigated. Using an excellent dataset from a repository investigation in saturated fractured rock at Sellafield, UK, with deep groundwater flow, a preliminary investigation of the effect of the addition of heat from HLW and SF on regional groundwater flow is undertaken. A coupled thermo-hydrogeological groundwater flow model dependent on fluid density and viscosity has been calibrated to field data, before heat is added to simulate waste. Substantial heating reduces fluid density and dynamic viscosity. Groundwater flows upwards through permeable damage zones of high-angle faults and increases natural velocity by 1.5×. Elevated groundwater temperatures are predicted at the surface in just hundreds of years. Travel times for conservative chemical species from the hypothetical repository to the St. Bees Sandstone aquifer are reduced by over one-third if engineered barriers fail at the point of containment, and remain reduced by hundreds of years for particles released thousands of years after containment. The results imply that in conditions similar to those modelled, the high-performance guarantee of the engineered barrier is essential to repository safety. A very good understanding of the coupled interaction of near-field heat and far-field groundwater flow will be important for safety cases, especially accuracy concerning heterogeneous fault discontinuities. It is necessary to model heat advection and faults at fractured sites.

Numerical modelling of coupled physical processes in bentonite–sand mixtures under the geological conditions is significant for designing and constructing sealing systems in deep underground repositories for highly radioactive nuclear waste. Within the framework of DECOVALEX 2015, Task A, this work presents the model validation of OpenGeoSys by numerical modelling of coupled hydromechanical (HM) processes in bentonite–sand mixtures. Parameters used in the HM model were determined by modelling the laboratory tests of the sealing experiment (SEALEX). Afterwards these parameters were applied for the modelling of a small-scale mock-up test considering the influence of technological gap and incidental fail of the seal in the sealing system. In order to investigate the availability of employing these HM parameters and numerical models directly to field predictions, the modelling results and measured data of an in situ SEALEX experiment were analysed comparatively. The modelling results reproduced well the main features in HM behaviour of the compacted bentonite–sand mixture, which denotes that the adopted HM models and parameters are adequate for describing the HM processes in the sealing system. It is necessary to take the elastoplastic behaviour and evolution of the permeability of bentonite–sand mixtures into account when using the adopted models to reproduce the HM processes of a sealing system.

Most of the current large scale hydrological models do not contain a physically-based groundwater flow component. The main difficulties in large-scale groundwater modeling include the efficient representation of unsaturated zone flow, the characterization of dynamic groundwater-surface water interaction and the numerical stability while preserving complex physical processes and high resolution. To address these problems, we propose a highly-scalable coupled hydrologic and groundwater model (mHM#OGS) based on the integration of two open-source modeling codes: the mesoscale hydrologic Model (mHM) and the finite element simulator OpenGeoSys (OGS). mHM#OGS is coupled using a boundary condition-based coupling scheme that dynamically links the surface and subsurface parts. Nested time stepping allows smaller time steps for typically faster surface runoff routing in mHM and larger time steps for slower subsurface flow in OGS. mHM#OGS features the coupling interface which can transfer the groundwater recharge and river baseflow rate between mHM and OpenGeoSys. Verification of the coupled model was conducted using the time-series of observed streamflow and groundwater levels. Moreover, we force the transient model using groundwater recharge in two scenarios: (1) spatially variable recharge based on the mHM simulations, and (2) spatially homogeneous groundwater recharge. The modeling result in first scenario has a slightly higher correlation with groundwater head time-series, which further validates the plausibility of spatial groundwater recharge distribution calculated by mHM in the mesocale. The statistical analysis of model predictions shows a promising prediction ability of the model. The offline coupling method implemented here can reproduce reasonable groundwater head time series while keep a desired level of detail in the subsurface model structure with little surplus in computational cost. Our exemplary calculations show that the coupled model mHM#OGS can be a valuable tool to assess the effects of variability in land surface heterogeneity, meteorological, topographical forces and geological zonation on the groundwater flow dynamics.

Early diagenesis affects the distribution of solutes and minerals in unconsolidated sediments. The investigation of diagenesis is critical to understanding the geochemical transformation and benthic fluxes of elements. During the cruise mission SO-177 in 2004, gravity coring samples were recovered in the Haiyang 4 Area of the northern slope of the South China Sea (SCS). The geochemical concentrations in interstitial water were determined onboard. The 1D C.CANDI reactive transport software was used to model the early diagenesis processes at four sites: 56-GC-3, 70-GC-9, 94-GC-11, and 118-GC-13. All of the simulations reproduced concentration profiles that matched the measurements with the implemented geochemical reactions. The degradation of organic carbon and anaerobic oxidation of methane (AOM) primarily determine the distribution of solutes in the working area. The degradation is active in the top 150 cm, and AOM is vigorous at depths below 200 cm. The local advective flux, sediment rate, and kinetic reaction constants of organic matter, methane and sulfate were calibrated based on the existing concentrations of pore water solutes. Geochemical reactions in this area occur in considerably deeper layers compared to depths cited in the literature. The model results provide evidence for the existence of deep hydrocarbon reservoirs that provide methane to the upper sediments.