Das Projekt "Water yield response to changes in land-use and climate in a semihumid/-arid transition region (Jinghe basin, Northwest China)" wird vom Umweltbundesamt gefördert und von Technische Universität Dresden, Institut für Bodenkunde und Standortslehre durchgeführt. The effort of vegetation restoration in recent decades has been effective for soil erosion control, but accompanied by a drastic reduction of water yield in the main tributaries of the Yellow River. This has led to an emerging debate notably about forest development. Increased temperature and decreased precipitation may also have contributed to water yield reduction. An essential key for developing an integrated land-use and water management approach is to understand and separate the hydrological response to changes in land use and climate. In this study on multiple scales ranging from single tree to watershed, water balance components, vegetation structure dynamics, and soil hydraulic properties will be investigated and continuously monitored on selected plots with vegetation typical to the region. Our research will be carried out in the semihumid/-arid transition region of Jinghe which is an important tributary of the Yellow River. We follow a nested approach on scales of plots and watersheds along a upstream/downstream situation in a representative subbasin. On the basis of our measurements, the process-oriented model BROOK90 will be implemented for predicting the water yield response to changes in climate and vegetation depending on relief and soil conditions. The results obtained from plot studies will be used to parameterize the distributed model SWIM. In a next step, SWIM will be fitted to the catchment discharge and to assess the effect of different land use and vegetation management on water yield. This assessment will provide a solid foundation for how much of the catchment area can be changed by vegetation restoration through forest management to maintain a certain level of water supply security that will ensure a more sustainable regional development.
Das Projekt "Sub project: Climate induced changes in phenology of lake plankton communities: Implications for the match / mismatch of species interactions" wird vom Umweltbundesamt gefördert und von Forschungsverbund Berlin, Leibniz-Institut für Gewässerökologie und Binnenfischerei durchgeführt. Long term studies suggest that seasonal succession in aquatic ecosystems is currently advancing in temperate latitudes. Those changes are likely to generate complex, and possibly time lagged responses leading to a decoupling (mismatch) of so far tightly coupled (matched) processes. Previous studies have basically focussed on individual species' responses to warming, while neglecting inter-specific interactions. Within AQUASHIFT we aim to identify past phase shifts and time-lagged responses in phyto- and zooplankton communities, and subsequent changes in species interaction induced by observed and projected climate warming. Our methodological approach is focussed on statistical data exploration, time series analysis, and modelling, based upon long-term records (24 years) of plankton, physical and chemical data from shallow, polymictic, eutrophic Müggelsee (Berlin). We anticipate to separate direct temperature driven responses from indirect responses through changes in thermal regime and species interaction. A stochastic and/or deterministic model will be created to describe the linkage between winter and spring meteorological conditions and vernal phytoplankton development in Müggelsee. Model development builds on previous statistical analysis and will be complemented by stochastic terms resulting from the parallel time series analysis. The model will be coupled to an existing lake physics model. This offline-coupled model system will be used to project changes in the timing and intensity of the phytoplankton spring blooms under a range of climate change scenarios.
Das Projekt "Steady-State Dilution and Mixing-Controlled Reactions in Three-Dimensional Heterogeneous Porous" wird vom Umweltbundesamt gefördert und von Eberhard Karls Universität Tübingen, Zentrum für Angewandte Geowissenschaften (ZAG), Arbeitsgruppe Hydrogeology durchgeführt. Understanding transport of contaminants is fundamental for the management of groundwater re-sources and the implementation of remedial strategies. In particular, mixing processes in saturated porous media play a pivotal role in determining the fate and transport of chemicals released in the subsurface. In fact, many abiotic and biological reactions in contaminated aquifers are limited by the availability of reaction partners. Under steady-state flow and transport conditions, dissolved reactants come into contact only through transverse mixing. In homogeneous porous media, transverse mixing is determined by diffusion and pore-scale dispersion, while in heterogeneous formations these local mixing processes are enhanced. Recent studies investigated the enhancement of transverse mixing due to the presence of heterogeneities in two-dimensional systems. Here, mixing enhancement can solely be attributed to flow focusing within high-permeability inclusions. In the proposed work, we will investigate mixing processes in three dimensions using high-resolution laboratory bench-scale experiments and advanced modeling techniques. The objective of the proposed research is to quantitatively assess how 3-D heterogeneity and anisotropy of hydraulic conductivity affect mixing processes via (i) flow focusing and de-focusing, (ii) increase of the plume surface, (iii) twisting and intertwining of streamlines and (iv) compound-specific diffusive/dispersive properties of the solute species undergoing transport. The results of the experimental and modeling investigation will allow us to identify effective large-scale parameters useful for a correct description of conservative and reactive mixing at field scales allowing to explain discrepancies between field observations, bench-scale experiments and current stochastic theory.
Das Projekt "Sub project: Hydrochemical and hydraulic properties of the continental upper crust at the KTB site" wird vom Umweltbundesamt gefördert und von Regierungspräsidium Freiburg, Abteilung 9 - Landesamt für Geologie, Rohstoffe und Bergbau durchgeführt. A constant rate pumping test of one year duration is planed to be carried out in the 4.0 km deep pilot hole of KTB. Watertable fluctuations in the pilot borehole and in the 9.1 km deep main borehole will be monitored as well. A wealth of data (pumping rate, watertable/ pressure, temperature, salinity/electrical conductivity, water samples,....) will become available, some even online. The first objective of the proposed project is to determine the flow system (type of aquifer model). From this deduced hydraulic model follow the hydraulic characteristics (such as: transmissivity, storage coefficient, fracture lengt/ width/aperture, permeability of fractures and matrix,....) describing the properties of the crystalline basement rocks in vicinity of the KTB pilot- and main hole. The length of the expect test radius is some 1000 m. The proposed project intends also to determine the degree of the hydraulic connection between the two holes (having a depth difference of 5.1 km). Additional information, such as water analyses, will be needed in interpreting the hydraulic data. A second major objective is the modelling of water-rock interaction (WRI) processes using the chemical data of KTB fluids. In particular the time series of chemical data will be used to model the kinetic and time dependent processes. We expect as well to see some breakthroughs of 'fresh, clean' crystalline basement water and another breakthrough resulting from fluid stored in the main hole and its surrounding.
Das Projekt "Extreme events in the past and future - A comparative assessment for the Hai He river and the Poyang lake basins" wird vom Umweltbundesamt gefördert und von Rheinische Friedrich-Wilhelms-Universität Bonn, Meteorologisches Institut durchgeführt. The impact of future climate change on land-use and water resource management is strongly dependent on the related changes in weather extremes. The future can only be assessed by the use of global climate models, which currently lack the necessary spatial resolution to represent such events. Moreover, global climate models are not able to incorporate all processes leading to extremes because of their low resolution. Thus downscaling of such runs is necessary, and only dynamical downscaling with high-resolution regional models is able to catch the necessary non-linear processes and process chains leading to extremes. The goal of this joint proposal is to provide estimates including their uncertainties of the behaviour of extreme weather events impacting land-use and water management for the 21st century for two climatically very different catchments, namely the Hai He river and the Poyang lake basins. To this goal we will first analyse the past of extreme events in both regions on the basis of observations and reanalysis data sets using state of the art extreme value statistics. Dynamical downscaling of global climate runs will be performed in order to evaluate the future of extreme events in the catchments. This necessitates first an evaluation of simulations of the current climate and its extremes by comparison with observations on a statistical basis. This will enable us to use the most appropriate regional climate model and to select the parametrisation setup most suitable for both regions, which might be different. While the Chinese partners will provide the observation data sets and perform the dynamical downscaling of global climate runs, the German partners will install the dynamical downscaling procedure at the Chinese partner institute, and generate the statistics of extremes both from observations and the simulations. The evaluation towards trends and uncertainties will be performed in close cooperation.
Das Projekt "A Scientific Review of the Global Water System" wird vom Umweltbundesamt gefördert und von Universität Kassel, Center for Environmental Systems Research durchgeführt. One of the important new insights of global environmental research has been the recognition of the existence of a global water system. This concept expands the long-accepted concept of the global physical water cycle to encompass biogeochemical, ecological and socioeconomic components. The recent launching of the Global Water System Project (GWSP) by the major global research organizations is a strong signal from the scientific community that key questions about this system need to be urgently studied. The objective of this one year project is to conduct a scientific review of the concept of the global water system by compiling and evaluating existing scientific literature and data bases and carrying out discussions with scientific experts. The review will identify key unresolved research questions. The scientific review will be divided into three parts (I) Describing the physical, biogeochemical, ecological and socio-political aspects of the global water system, (II) Elaborating cross-cutting linkages in the global water system, (III) Identifying major unresolved questions & research priorities. To ensure that the perspectives of developing countries are also taken into account, the Antragssteiler proposes to spend 6 months out of the 12-month project at the National Institute of Advanced Studies in Bangalore. This will be a fully independent (eigenständiges) and alone-standing project conducted within the framework of the GWSP (of which the Antragssteiler is Co-Chair). It is expected that the scientific review will make a major contribution to setting priorities in global water research over the coming years.
Das Projekt "Pockmark like structures in Lake Constance and their effects on methane emission from large lakes" wird vom Umweltbundesamt gefördert und von Stiftung Alfred-Wegener-Institut für Polar- und Meeresforschung in der Helmholtz-Gemeinschaft, Biologische Anstalt Helgoland (Institut BAH) durchgeführt. The role of lakes in the global methane budget seems to be more important than previously thought. However, the sources and the sinks of this climate active gas in large lakes are still quite unknown. Beside diffusive flux or ebullition due to high microbiological methane production, another potentially important methane source is the emission of fluids and gas from the deeper geosphere, such as methane seeps or pockmarks. Pockmarks are depressions at the sediment surface, often characterized by fluid flow and sites of enhanced methane release. Numerous pockmarks have been described for the marine environment, but pockmarks in limnic systems are rather unknown, as well as their associated geological, chemical and biological processes. In Lake Constance (southern Germany) pockmark like structures have been discovered recently. In a preliminary survey in 2005, we were able to observe methane ebullition and increased methane concentrations in the adjacent water column at these pockmarks. The objectives of this study are (1) to locate and to describe the pockmark areas in Lake Constance, (2) to identify the mechanisms responsible for the formation of pockmarks in Lake Constance, (3) to identify the sources of methane and (4) to quantify the fluxes of methane from the lake floor and their temporal variability.
Das Projekt "Sub project: Electron transfer reactions at iron mineral surfaces in the presence of organic sorbates" wird vom Umweltbundesamt gefördert und von Universität Tübingen, Zentrum für Angewandte Geowissenschaften - Umweltmineralogie und Umweltchemie durchgeführt. Redox reactions at iron mineral surfaces play an important role in determining the overall biogeochemical milieu in anoxic groundwater systems. Previous studies have shown that oxidation of sorbed ferrous iron at mineral phases may cause remodelling of the mineralwater interphase and thus may affect electron transfer processes in anoxic aquifers. In the first funding period, we studied in detail how and at which conditions oxidation of ferrous iron at mineral surfaces affects electron transfer processes. Using carbon tetrachloride (CCl4) as model oxidant, we could further demonstrate, that the proposed reactive tracer approach, which is based on changes of the stable isotopic composition of model oxidants, could be successfully applied to characterize the surface reactivity and dynamics of surface bound Fe(II) species at iron(III)hydroxides. Up to date, process based studies on surface mediated transformation of redox active solutes in iron mineral systems have been conducted primarily in model systems devoid of natural organic matter. In natural systems, however, mineral surfaces are inevitably in contact with OM. Sorbed DOM is likely to affect heterogeneous electron transfer processes due to its interactions with iron both in aqueous solution and at the mineral surface. On one hand, DOM sorption at iron hydroxides may interfere with the formation of reactive Fe(II) surface sites. On the other hand, DOM contain redox active quinone moieties and may act as a mediator enhancing the electron-transfer across the mineral surface. In this follow-up project we propose to investigate the effects of various organic sorbates such as redox-inert organic acids as well as redox-active quinones, humic substances and DOM on electron transfer reactions at iron mineral surfaces. Furthermore, we will investigate the effects of sulfide as additional redox active natural component on DOM-iron interfacial redox processes.
Das Projekt "Sub project: Mass transfer, aging and reactions at NAPL interfaces in porous media" wird vom Umweltbundesamt gefördert und von Universität Tübingen, Zentrum für Angewandte Geowissenschaften - Umweltmineralogie und Umweltchemie durchgeführt. Release of non-aqueous phase liquids (NAPLs) into natural porous media is a widespread environmental problem. Transfer of pollutants across the NAPL-water phase boundary determines both the extent of groundwater contamination as well as the persistence of residual NAPL phases in porous media. Previous research has shown that NAPL-water interfaces are subject to 'aging' phenomena in aqueous environments, e.g., development of skin-like viscous films. However, surprisingly litte is known about the factors and mechanisms that control such film formation of NAPLs in aqueous porous media and about the effects of such films on mass transfer of organic contaminants from the NAPL to the aqueus phase. In the proposed project we will address these knowledge gaps in order to (i) achieve a process based understanding of reactions and environmental conditions leading to the formation of viscous phase boundaries of NAPLs in porous media (aging) and to (ii) develop and vali-date a physical model of such boundary layers to quantify time-dependent interfacial phenomena in multi-component NAPL-water systems (mass transfer). To this end we will carry out batch and flow-through experiments with model and real NAPLs in water and aqueous porous media and make intense use of chemical probe techniques. We will utilize chemical and rheological analysis, microscopic process modeling and, in cooperation with partners within the research group, we will apply new designs of spectroscopic and electrochemical tools for spatially highly resolved investigations of the interface as well as contribute to reactive transport modeling at NAPL-contaminated porous media.
Das Projekt "Causes, kinetics and reversal of clogging in injection wells" wird vom Umweltbundesamt gefördert und von Brandenburgische Technische Universität Cottbus-Senftenberg, Fakultät 2: Umwelt und Naturwissenschaft, Lehrstuhl Hydrologie durchgeführt. Overexploitation of aquifers and depletion of groundwater quality is becoming more and more important worldwide. Artificial recharge can help to avoid these problems. Worldwide injection wells are used to infiltrate surface water into aquifers. The main problem using this technique is clogging of the well screen, filter and the nearby aquifer which results into a decrease of hydraulic conductivity of the aquifer. Clogging is mainly caused by physical deposition of fine particles at the aquifer matrix, by geochemical reactions, air entrapment and growth of biofilms. The pore volume is reduced by these processes and therefore the hydraulic conductivity of the aquifer. A possibility for redevelopment of the aquifer is back-washing which allows rising the hydraulic conductivity again. More or less each process has been investigated experimentally but the interactions of all processes are rarely addressed. A numerical model is necessary to analyse all the different effects causing clogging. The model will allow taking precautions in terms of quality of infiltration water and how to redevelop already clogged wells as important criteria for the selection of appropriate measures for groundwater recharge. Keywords: artificial recharge, clogging processes
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