Bayerisches Landesamt für Umwelt

Groundwater recharge is the main forcing of regional groundwater flow. In traditional partial‐differential‐equation (pde)‐based models that treat aquifers as separate compartments, groundwater recharge needs to be defined as a boundary condition or it is a coupling condition to other compartments. Integrated models that treat the vadose and phreatic zones as a continuum allow for a more sophisticated calculation of subsurface fluxes, as feedbacks between both zones are captured. However, they do not contain an explicit groundwater‐recharge term so it needs to be estimated by post‐processing. Groundwater recharge consists of changes in groundwater storage and of the flux crossing the water table, which can be calculated based on hydraulic gradients. We introduce a method to evaluate the change of groundwater storage by a time‐cumulative water balance over the depth section of water table fluctuations, avoiding the use of a specific yield. We demonstrate the approach first by a simple 1‐D vertical model that does not allow for lateral outflow and illustrates the ambiguity of computing groundwater recharge by different methods. We then apply the approach to a 3‐D model with a complex topography and subsurface structure. The latter example shows that groundwater recharge is highly variable in space and time with notable differences between regional and local estimates. Local heterogeneity of topography or subsurface properties results in complex redistribution patterns of groundwater. In fully integrated models, river‐groundwater exchange flow may severely bias the estimate of groundwater recharge. We, therefore, advise masking out groundwater recharge at river locations.

In diesem Kapitel wird dargestellt, in welcher Weise die Wasserwirtschaft auf die oft gewässerökologisch und hydromorphologisch nachteiligen nutzungsgedingten Veränderungen der Fließgewässer und gewässernahen Bereiche reagiert. Die ersten Anfänge der „naturnahen“ Gewässer- und Auenentwicklung reichen bis in die 1970er-Jahre zurück. Beständig wurden diese zaghaften ersten, hauptsächlich wasserwirtschaftlichen Maßnahmen, um naturschutzfachliche und gewässerökologische Komponenten erweitert und verfeinert. Mit Einführung der EG-Wasserrahmenrichtlinie im Jahre 2000 wurde erstmals eine flussgebietsorientierte Bewirtschaftung eingeführt, die im Zusammenwirken mit anderen europäischen Richtlinien (RL) (u. a. FFH-Richtlinie, Hochwasserrisikomanagement-Richtlinie, Grundwasser-Richtlinie, Kommunale Abwasser-Richtlinie) zu einer ökologischen Verbesserung der Fließgewässer beitragen.

Dieses Kapitel zeigt, in welcher Weise der Mensch mit den Gewässern verbunden ist. Es beginnt mit der Darstellung der frühen Nutzungen, wie zum Beispiel Flößerei, Teichwirtschaft und Wassermühlen. Heute sind es bei den größeren Gewässern vornehmlich Schifffahrt und Wasserkraftnutzung. Ein ständiges Thema ist der nutzungsbedingte Ausbau der Fließgewässer und der Hochwasserschutz. Im Kapitel wird gezeigt, dass nahezu jede Nutzungsform Auswirkungen auf die Entwicklung von Fließgewässer und Aue hat. Um Fließgewässer- und Auen im Spannungsfeld von Wirtschaftlichkeit und Nutzungsanforderungen nachhaltig entwickeln zu können, müssen diese Zusammenhänge bei Planungen berücksichtigt werden. Im Buch wird bei der Beschreibung der anthropogenen Einwirkungen auf Fließgewässer und Auen zwischen frühen, historischen Nutzungen und Einwirkungen im Zuge der zunehmenden Industrialisierung unterschieden. Wertfrei wird dargestellt, wie der Mensch im Laufe der Zeit die Fließgewässer und Auen zu seinem Nutzen verändert hat und welche Auswirkungen im Hinblick auf deren Entwicklung damit verbunden sind.

Zusammenfassung Der Beitrag untersucht Grenzlinien der Solidarität. Er betrachtet, wie in Krisensituationen Unterstützungsbedarfe für jene soziale Gruppen verhandelt werden, die in etablierten Solidaritätsdiskursen in eine Deutungslücke fallen. Untersuchungsgegenstand bildet die öffentliche Verhandlung von Solidarität mit Soloselbstständigen zu Beginn der Coronapandemie. Gestützt auf Auswertungen von 21 qualitativen Interviews und ein Textkorpus mit 2428 Zeitungsartikeln zeichnen wir den Diskurs um Soforthilfe nach. Mittels einer Kombination aus strukturierender Inhaltsanalyse und Textmining zeigen wir auf, dass die Deutungsfigur der Marktabhängigkeit von Soloselbstständigen in dieser Krisenzeit dazu dient, die Hilfsbedürftigkeit der Gruppe zu identifizieren (soziale Grenzziehung), aber auch die Ausgestaltung der Hilfe kontrovers zu diskutieren (substanzielle Grenzziehung). Wir zeigen, wie sich Solidaritätsnormen im Diskursverlauf konfigurieren und dabei Marktabhängigkeit als relevante Grenze für Solidarität freigeben, diese aber nur zeitlich begrenzt wirksam bleibt.

In diesem Kapitel werden 12 Beispiele von Fließgewässer- und Auenentwicklungsmaßnahmen aus unterschiedlichen Naturräumen und Ausgangsbedingungen vor Ort vorgestellt. Einige der Beispiele waren bereits in der Erstauflage enthalten, so dass diese fortgeschrieben werden konnten. Sie zeigen die Entwicklung der letzten 10 Jahre und ermöglichen einen direkten Vergleich zwischen den damaligen Zielen und dem nun Erreichten.

Dieses Kapitel zeigt, dass die Grundlage einer erfolgreichen Fließgewässer- und Auenentwicklung die naturraumangepasste Planung unter Berücksichtigung wasserwirtschaftlicher, gewässerökologischer und naturschutzfachlicher Grundlagen ist. Eine Besonderheit stellt dabei die Planung im urbanen Umfeld dar. Einflüsse auf die Entwicklungsprozesse im Wasserkörper und auf den gewässernahen Flächen (Uferstreifen und Gewässeraue) hat dabei im besonderen Maße die Fließgewässerunterhaltung. Eine umfassende Öffentlichkeitsbeteiligung verbessert die Akzeptanz jeder Maßnahme. Die Finanzierung ist eine Grundvoraussetzung für die Realisierung eines Projekts. Hierzu werden in diesem Kapitel einige Beispiele vorgestellt.

Fließgewässer und die gewässerbegleitenden Uferstreifen und Auen sind in ihrer Funktion als Ökosystem durch ein zeitlich wie räumlich äußerst dynamisches Prozessgeschehen gekennzeichnet. Die Ökosystembausteine, die Besiedlungsdynamik und die ökosystemaren Zusammenhänge sind u. a. Grundbedingung für die sehr speziellen Lebensräume und Lebensgemeinschaften im Wasserkörper und in der angrenzenden Gewässeraue. Ebenso wie die gewässermorphologische Ausprägung des Wasserkörpers sind diese Prozesse Grundlage der Fließgewässer- und Auentypologie.

Microplastic (MP) contamination of freshwater ecosystems is still in the focus of research and public attention, as aquatic environments have a high ecological, economic, and recreational value. We now know that rivers do not only function as pathways of MPs into oceans but may also act as temporary MP sinks. However, due to methodological differences, the comparability of studies on MP contamination of rivers is still limited. To compare MP contamination between different river systems, to analyze if there is a constant increase in MP contamination from the upper to the lower course of the river, and to investigate if there are distinct MP distribution patterns, we set up a large-scale survey. We chose two large river systems, the Rhine and Danube catchments with their tributaries and sampled 23 rivers of different sizes at 53 sampling locations in southwest Germany. Surface water sampling, sample processing, and analysis were performed with the same methodology to obtain comparable results on MP number, polymer type, and particle’s size and shape. Fully quantitative data were generated down to 300 µm by using a manta trawl net with a 300-µm mesh size for sampling. Nevertheless, we also included the non-quantitative sampled fraction of particles down to a size of 20 µm in our FTIR analysis after plastic-friendly sample purification by enzymatic oxidative treatment. Plastic concentrations recorded in surface water at the sampling locations ranged from 0.7 to 354.9 particles/m³. Concerning all samples, the number of particles increased toward lower size classes (61.0 ± 34.2% below 300 µm), and fragments were the prevailing shape (90.7 ± 13.6%). Polyethylene (49.2 ± 25.9%) and polypropylene (33.2 ± 22.6%) were the most frequent polymer types. Our survey did not reveal distinct MP distribution patterns or a constant increase of MP abundance within river courses in the investigated river systems. Next, to provide a large-scale dataset of microplastic contamination in surface waters of southwest Germany, our study shows that a representative sampling of MPs in rivers is challenging. MP particles are not homogeneously distributed in rivers, and this indicates that spatial and temporal changes in MP abundance should always be considered in MP monitoring approaches.

In the summer months of June to August 2021, heavy precipitation and prolonged persistent rain led to local flooding and extreme flood events in Bavaria. Numerous regions throughout Bavaria were affected and a disaster situation was declared in three districts. The review gives an overview of the situation in Berchtesgadener Land. Furthermore, an example from the Oberallgäu illustrates the problem of extreme bedload transport in combination of piped torrents against the background of the events. The extreme flood event on the rivers Aisch, Zenn and Frankish Rezat west of the metropolitan region of Nuremberg is also described in detail. Such events can have enormous negative impacts on people, the cultural heritage, the economy and the environment and are expected to become more frequent as climate change progresses. For this reason, investigations and measures for dealing with the risk of flooding are also presented in this review.

In the course of the broad expansion of organic farming, a considerable increase in the number of different cultivation types has also occurred. Compared to the formerly ideal forms with arable farming and animal husbandry around 0.5–1.0 LU ha−1 and the corresponding use of organic manure, an increasing differentiation of cultivation systems can be observed today. There are market crop systems without livestock and purchased fertilizer with less than 20% legumes and forage cropping systems with more than 2.5 LU ha−1 livestock and a cultivation of grain and forage legumes of more than 50% in the crop rotations. From a long list of corresponding survey studies of farms in agricultural practice as well as a number of important long-term field trials, in this overview paper it was possible to investigate and to discuss both the manifold possibilities and the limitations of intensification in organic agriculture by a comparative analysis of results from a wide range of cropping systems from Central Europe. The short-term as well as the long-term effects on the development of yield and quality performance of crop rotations, nutrient management, and soil fertility, as well as of important environmental effects, were quantified, and aspects of further development and sustainability of organic farming systems were shown in detail.

Organic farming systems have become widespread in recent decades due to their popularity with consumers and their beneficial effects on the environment and biodiversity. Through the increasing number of available studies from farm surveys and comparable results from long-term field trials, the various real existing forms and intensities of agricultural management were subjected to a closer examination in this review. In this paper, the mean characteristics and the range of variation in crop productivity, crop quality and soil fertility as well as the importance and the extent of environmental impacts are comparatively analyzed. From widespread cultivation systems and forms of nutrient management from Central Europe with a focus on Germany, the following fields of influence were investigated and conclusions for the future optimal design of organic cultivation methods were listed: site, soil conditions, climate, phases of conversion and consolidation, crop rotations and farm structures, application of organic and mineral fertilizer types.

Anthropogenic climate change is challenging biodiversity conservation worldwide. Climate change metrics derived from future climate predictions help to assess potential impacts of climate change on biodiversity. Here we calculated future climate change velocities across biogeographical regions of terrestrial Europe and the Natura 2000 protected area network, the largest protected area network on Earth. We applied climate projections for the year 2070, considering two emission scenarios, six global climate models and a fine spatial resolution. Areas with very high climate change velocity were identified as climate change hotspots, while areas with very low velocity were recognized as coldspots. We further revealed where and to what extent climate change hotspots and coldspots coincide with Natura 2000 sites. We found that climate change velocities are projected highest in the Continental and Boreal regions, and lowest in the Mediterranean and Anatolian regions. However, the Alpine region will likely contain largest areal proportions of climate change hotspots, while areal proportions of coldspots are projected largest in the Mediterranean region. High mountain regions such as the Alps show a high proportion of Natura 2000 sites that coincide with climate change hotspots. Both, hotspots and coldspots, are geographically associated with areas of topographic diversity. Low topographical diversity indicates high climate change exposure. The impact of hotspots increases with spatial isolation. Oceanic climate buffers climate change exposure in contrast to continental climate. However, continental regions of Europe tend to exhibit less spatial isolation. We recommend conservation action in climate change hotspots and coldspots to simultaneously protect the most climate-exposed biodiversity as well as climate change refugia. Climate change hotspots and coldspots overlapping with Natura 2000 sites should be considered priority conservation sites because new protected areas are hard to realize in densely populated landscapes of Europe. This study directs European conservation management and policy towards meeting international conservation goals in a climate-smart way.

Recent climate and land-use changes are having substantial impacts on biodiversity, including population declines, range shifts, and changes in community composition. However, few studies have compared these impacts among multiple taxa, particularly because of a lack of standardized time series data over long periods. Existing data sets are typically of low resolution or poor coverage, both spatially and temporally, thereby limiting the inferences that can be drawn from such studies. Here, we compare climate and land-use driven occupancy changes in butterflies, grasshoppers, and dragonflies using an extensive data set of highly heterogeneous observation data collected in the central European region of Bavaria (Germany) over a 40-year period. Using occupancy models, we find occupancies (the proportion of sites occupied by a species in each year) of 37% of species have decreased, 30% have increased and 33% showed no significant trend. Butterflies and grasshoppers show strongest declines with 41% of species each. By contrast, 52% of dragonfly species increased. Temperature preference and habitat specificity appear as significant drivers of species trends. We show that cold-adapted species across all taxa have declined, whereas warm-adapted species have increased. In butterflies, habitat specialists have decreased, while generalists increased or remained stable. The trends of habitat generalists and specialists both in grasshoppers and semi-aquatic dragonflies, however did not differ. Our findings indicate strong and consistent effects of climate warming across insect taxa. The decrease of butterfly specialists could hint towards a threat from land-use change, as especially butterfly specialists' occurrence depends mostly on habitat quality and area. Our study not only illustrates how these taxa showed differing trends in the past but also provides hints on how we might mitigate the detrimental effects of human development on their diversity in the future.

There are considerable synergies of the Water Framework Directive (WFD) and Natura 2000 (N2K) as both directives focus on aquatic ecosystems and try to reach a good or better ecological status for them. Although there are also differences that have to be mastered in terms of objectives, instruments and involved stakeholders. An important approach in Bavaria has ever been the integration of N2K objectives and measures into the WFD's River basin management plans. The hydromorphological measures listed in the river basin managements plans are implemented in different ways: There is firstly a continuous implementation in river restoration measures and projects carried out by the water management authorities throughout the country. Secondly Integrated Ecological Management Plans ("Ökologische Entwicklungskonzepte") are set up together by water and conservation authorities: Integrated planning on the regional or local level is especially possible when the N2K sites and the WFD water body overlap predominantly. Thirdly there are outstanding projects like LIFE Nature project "Flusserlebnis Isar" showing what can be achieved when everybody is working together based on common intentions and supported by EU funding.

Natural factors shape the morphology and the balance of water and solid materials of our streams. Hydraulic engineering interventions influence these factors and, consequently, the natural stream morphology. In light of this, the hydromorphological processes that are still taking place or can be initiated are of particular interest. Yet this requires a basic level of river morphology. The goal is to envisage sustainable measures that ideally enable a self-dynamic development and require only little or no subsequent intervention.

We studied diatoms from the fifteen springs selected in the Berchtesgaden National Park on be-half of the Bavarian State Ministry for the Environment to be sentinel environments of cli-mate-change effects. For three of these springs, diatom data based on samples taken in 1997 were also available. A total of 162 species belonging to 49 genera were found sampling three micro-habitat types (lithic materials, bryophytes, surface sediments). The cumulative percentage of all species included in a threat category including endangered species was 43%, confirming previ-ous findings for comparable environments of the Alps. We could find a statistically significant positive association between the Meinzer variability index for discharge and the cumulative rel-ative abundance of aerial diatom species. This study thus highlighted once again the relevance of discharge (and associated water-level) variability as an environmental determinant of diatom assemblages in spring ecosystems. Increased nitrate concentrations in some springs, likely due to diffuse airborne pollution and, locally, to impacts such as forest management, game, and cat-tle, led to a relevant occurrence of eutraphentic diatom species. Our results show a segregation of the older data in non-parametric diatom-based ordinations, suggesting a strong potential for the use of spring diatoms in studies aiming at tracking the effects of climate and environmental change.

Durch die projizierte globale Erwärmung werden sich Hitzeextreme verschärfen. Vor allem in den Städten wird die Lebensqualität der Stadtbevölkerung unter sommerlichen Hitzewellen leiden. Im Projekt HeatResilientCity werden bewohnerorientierte Hitzeanpassungsmaßnahmen an Gebäuden und im städtischen Freiraum entwickelt und geprüft sowie Empfehlungen für die Umsetzung gegeben.The HeatResilientCity project applied insights from natural sciences, engineering and the social sciences to develop heat adaptation measures, test their effectiveness and partially implement them in two structurally different real-world laboratories in Dresden-Gorbitz and Erfurt-Oststadt. The present article discusses interventions to plant street trees and to refurbish two different residential buildings. We describe and analyse aspects of the implementation process to identify key factors that enable or constrain adaptation action among different groups of actors. We find that adaptation measures that are objectively effective and supported by residents are most appropriate for implementation. Where residents evince scepticism about adaptation measures, information about their effectiveness and usefulness should be disseminated. Early and targeted involvement of relevant stakeholders, careful communication and the establishment of climate adaptation as a permanent interdepartmental task at municipal level can promote successful implementation of heat adaptation measures.

Organic matter (OM) and nutrient nitrogen (N) play vital roles in the fertility and production of soil in accordance with goals of efficient environmental protection. This study aimed to show the extent to which N delivery can contribute to improving nitrogen fertilizer requirements (NFR) through comparative analysis of OM and N. Systems determining the NFR in agricultural practices have thus far been challenged to estimate the annual rate of mineralization of the soil. OM and N turnover was investigated through an available evaluation consisting of 546 representatively distributed permanent test and observation plots (TP) of the German Federal State of Saxony farms. A solid database of at least 10-year field plot card records from 2001 to 2010 was selected for the analysis. A program (BEFU) widely used in agricultural practice, along with the simplified process model CCB, were applied. For the calculation of the amount of mineral N fertilizers used, the results of three different methods for determining the NFR were compared with each other. The determination of the farmers’ demand (=actual condition of the TP) with a mean value of 132 kg N ha−1 did not show a large difference between the calculated values with 137 kg N ha−1 by the BEFU program. Based on the available results for the most important crop species cultivated in Saxony, there were clear differences in the considerations of the N delivery from the soil. The BEFU program was able to calculate an average N delivery of 17 kg N ha−1 from tabulated data, whereas with the CCB process model, 66 kg N ha−1 of mineralization was determined with a distinct higher deviation by taking into account the 10-year field histories. Using the N delivery of the TP by the CCB model, a clear reduction of the mean N fertilization level, to about 80 kg N ha−1, was therefore achieved. These differences were particularly large for TP with organic fertilization (livestock), at a relatively low N fertilization level, and for certain crop species. With a high standard deviation, the average savings potential of mineral N fertilizers was 52–57 kg N ha−1. After including the corrected values for the N mineral fertilization, a decrease in the N balances by an average of 20–25 kg N ha−1 was ultimately achieved. In particular, the heavily oversupplied plots with D and E classification decreased by approximately 50%. The results of our study demonstrate clear improvements; therefore, increased efforts should be made in the future to optimize the determination of NFR using applicable methods that consider N mineralization in agricultural practice and consultation.