@phdthesis{Schmitz2023,
  author    = {Schmitz, Se{\´a}n},
  title     = {Using low-cost sensors to gather high resolution measurements of air quality in urban environments and inform mobility policy},
  doi       = {10.25932/publishup-60105},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-601053},
  school      = {Universit{\"a}t Potsdam},
  pages     = {180},
  year      = {2023},
  abstract  = {Air pollution has been a persistent global problem in the past several hundred years. While some industrialized nations have shown improvements in their air quality through stricter regulation, others have experienced declines as they rapidly industrialize. The WHO's 2021 update of their recommended air pollution limit values reflects the substantial impacts on human health of pollutants such as NO2 and O3, as recent epidemiological evidence suggests substantial long-term health impacts of air pollution even at low concentrations. Alongside developments in our understanding of air pollution's health impacts, the new technology of low-cost sensors (LCS) has been taken up by both academia and industry as a new method for measuring air pollution. Due primarily to their lower cost and smaller size, they can be used in a variety of different applications, including in the development of higher resolution measurement networks, in source identification, and in measurements of air pollution exposure. While significant efforts have been made to accurately calibrate LCS with reference instrumentation and various statistical models, accuracy and precision remain limited by variable sensor sensitivity. Furthermore, standard procedures for calibration still do not exist and most proprietary calibration algorithms are black-box, inaccessible to the public. This work seeks to expand the knowledge base on LCS in several different ways: 1) by developing an open-source calibration methodology; 2) by deploying LCS at high spatial resolution in urban environments to test their capability in measuring microscale changes in urban air pollution; 3) by connecting LCS deployments with the implementation of local mobility policies to provide policy advice on resultant changes in air quality. In a first step, it was found that LCS can be consistently calibrated with good performance against reference instrumentation using seven general steps: 1) assessing raw data distribution, 2) cleaning data, 3) flagging data, 4) model selection and tuning, 5) model validation, 6) exporting final predictions, and 7) calculating associated uncertainty. By emphasizing the need for consistent reporting of details at each step, most crucially on model selection, validation, and performance, this work pushed forward with the effort towards standardization of calibration methodologies. In addition, with the open-source publication of code and data for the seven-step methodology, advances were made towards reforming the largely black-box nature of LCS calibrations. With a transparent and reliable calibration methodology established, LCS were then deployed in various street canyons between 2017 and 2020. Using two types of LCS, metal oxide (MOS) and electrochemical (EC), their performance in capturing expected patterns of urban NO2 and O3 pollution was evaluated. Results showed that calibrated concentrations from MOS and EC sensors matched general diurnal patterns in NO2 and O3 pollution measured using reference instruments. While MOS proved to be unreliable for discerning differences among measured locations within the urban environment, the concentrations measured with calibrated EC sensors matched expectations from modelling studies on NO2 and O3 pollution distribution in street canyons. As such, it was concluded that LCS are appropriate for measuring urban air quality, including for assisting urban-scale air pollution model development, and can reveal new insights into air pollution in urban environments. To achieve the last goal of this work, two measurement campaigns were conducted in connection with the implementation of three mobility policies in Berlin. The first involved the construction of a pop-up bike lane on Kottbusser Damm in response to the COVID-19 pandemic, the second surrounded the temporary implementation of a community space on B{\"o}ckhstrasse, and the last was focused on the closure of a portion of Friedrichstrasse to all motorized traffic. In all cases, measurements of NO2 were collected before and after the measure was implemented to assess changes in air quality resultant from these policies. Results from the Kottbusser Damm experiment showed that the bike-lane reduced NO2 concentrations that cyclists were exposed to by 22 ± 19\%. On Friedrichstrasse, the street closure reduced NO2 concentrations to the level of the urban background without worsening the air quality on side streets. These valuable results were communicated swiftly to partners in the city administration responsible for evaluating the policies' success and future, highlighting the ability of LCS to provide policy-relevant results. As a new technology, much is still to be learned about LCS and their value to academic research in the atmospheric sciences. Nevertheless, this work has advanced the state of the art in several ways. First, it contributed a novel open-source calibration methodology that can be used by a LCS end-users for various air pollutants. Second, it strengthened the evidence base on the reliability of LCS for measuring urban air quality, finding through novel deployments in street canyons that LCS can be used at high spatial resolution to understand microscale air pollution dynamics. Last, it is the first of its kind to connect LCS measurements directly with mobility policies to understand their influences on local air quality, resulting in policy-relevant findings valuable for decisionmakers. It serves as an example of the potential for LCS to expand our understanding of air pollution at various scales, as well as their ability to serve as valuable tools in transdisciplinary research.},
  language  = {en}
}
@article{SeleemAyzelBronstertetal.2023,
  author    = {Seleem, Omar and Ayzel, Georgy and Bronstert, Axel and Heistermann, Maik},
  title     = {Transferability of data-driven models to predict urban pluvial flood water depth in Berlin, Germany},
  series = {Natural Hazards and Earth System Sciences},
  volume    = {23},
  journal   = {Natural Hazards and Earth System Sciences},
  number    = {2},
  publisher = {Copernicus},
  address   = {G{\"o}ttingen},
  issn      = {1684-9981},
  doi       = {10.5194/nhess-23-809-2023},
  pages     = {809 -- 822},
  year      = {2023},
  abstract  = {Data-driven models have been recently suggested to surrogate computationally expensive hydrodynamic models to map flood hazards. However, most studies focused on developing models for the same area or the same precipitation event. It is thus not obvious how transferable the models are in space. This study evaluates the performance of a convolutional neural network (CNN) based on the U-Net architecture and the random forest (RF) algorithm to predict flood water depth, the models' transferability in space and performance improvement using transfer learning techniques. We used three study areas in Berlin to train, validate and test the models. The results showed that (1) the RF models outperformed the CNN models for predictions within the training domain, presumable at the cost of overfitting; (2) the CNN models had significantly higher potential than the RF models to generalize beyond the training domain; and (3) the CNN models could better benefit from transfer learning technique to boost their performance outside training domains than RF models.},
  language  = {en}
}
@misc{SeleemAyzelBronstertetal.2023,
  author    = {Seleem, Omar and Ayzel, Georgy and Bronstert, Axel and Heistermann, Maik},
  title     = {Transferability of data-driven models to predict urban pluvial flood water depth in Berlin, Germany},
  series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {1323},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-58916},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-589168},
  pages     = {809 -- 822},
  year      = {2023},
  abstract  = {Data-driven models have been recently suggested to surrogate computationally expensive hydrodynamic models to map flood hazards. However, most studies focused on developing models for the same area or the same precipitation event. It is thus not obvious how transferable the models are in space. This study evaluates the performance of a convolutional neural network (CNN) based on the U-Net architecture and the random forest (RF) algorithm to predict flood water depth, the models' transferability in space and performance improvement using transfer learning techniques. We used three study areas in Berlin to train, validate and test the models. The results showed that (1) the RF models outperformed the CNN models for predictions within the training domain, presumable at the cost of overfitting; (2) the CNN models had significantly higher potential than the RF models to generalize beyond the training domain; and (3) the CNN models could better benefit from transfer learning technique to boost their performance outside training domains than RF models.},
  language  = {en}
}
@phdthesis{Seleem2023,
  author    = {Seleem, Omar},
  title     = {Towards urban pluvial flood mapping using data-driven models},
  doi       = {10.25932/publishup-59813},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-598137},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xv, 95},
  year      = {2023},
  abstract  = {Casualties and damages from urban pluvial flooding are increasing. Triggered by short, localized, and intensive rainfall events, urban pluvial floods can occur anywhere, even in areas without a history of flooding. Urban pluvial floods have relatively small temporal and spatial scales. Although cumulative losses from urban pluvial floods are comparable, most flood risk management and mitigation strategies focus on fluvial and coastal flooding. Numerical-physical-hydrodynamic models are considered the best tool to represent the complex nature of urban pluvial floods; however, they are computationally expensive and time-consuming. These sophisticated models make large-scale analysis and operational forecasting prohibitive. Therefore, it is crucial to evaluate and benchmark the performance of other alternative methods. The findings of this cumulative thesis are represented in three research articles. The first study evaluates two topographic-based methods to map urban pluvial flooding, fill-spill-merge (FSM) and topographic wetness index (TWI), by comparing them against a sophisticated hydrodynamic model. The FSM method identifies flood-prone areas within topographic depressions while the TWI method employs maximum likelihood estimation to calibrate a TWI threshold (τ) based on inundation maps from the 2D hydrodynamic model. The results point out that the FSM method outperforms the TWI method. The study highlights then the advantage and limitations of both methods. Data-driven models provide a promising alternative to computationally expensive hydrodynamic models. However, the literature lacks benchmarking studies to evaluate the different models' performance, advantages and limitations. Model transferability in space is a crucial problem. Most studies focus on river flooding, likely due to the relative availability of flow and rain gauge records for training and validation. Furthermore, they consider these models as black boxes. The second study uses a flood inventory for the city of Berlin and 11 predictive features which potentially indicate an increased pluvial flooding hazard to map urban pluvial flood susceptibility using a convolutional neural network (CNN), an artificial neural network (ANN) and the benchmarking machine learning models random forest (RF) and support vector machine (SVM). I investigate the influence of spatial resolution on the implemented models, the models' transferability in space and the importance of the predictive features. The results show that all models perform well and the RF models are superior to the other models within and outside the training domain. The models developed using fine spatial resolution (2 and 5 m) could better identify flood-prone areas. Finally, the results point out that aspect is the most important predictive feature for the CNN models, and altitude is for the other models. While flood susceptibility maps identify flood-prone areas, they do not represent flood variables such as velocity and depth which are necessary for effective flood risk management. To address this, the third study investigates data-driven models' transferability to predict urban pluvial floodwater depth and the models' ability to enhance their predictions using transfer learning techniques. It compares the performance of RF (the best-performing model in the previous study) and CNN models using 12 predictive features and output from a hydrodynamic model. The findings in the third study suggest that while CNN models tend to generalise and smooth the target function on the training dataset, RF models suffer from overfitting. Hence, RF models are superior for predictions inside the training domains but fail outside them while CNN models could control the relative loss in performance outside the training domains. Finally, the CNN models benefit more from transfer learning techniques than RF models, boosting their performance outside training domains. In conclusion, this thesis has evaluated both topographic-based methods and data-driven models to map urban pluvial flooding. However, further studies are crucial to have methods that completely overcome the limitation of 2D hydrodynamic models.},
  language  = {en}
}
@article{HeistermannFranckeScheiffeleetal.2023,
  author    = {Heistermann, Maik and Francke, Till and Scheiffele, Lena and Petrova, Katya Dimitrova and Budach, Christian and Schr{\"o}n, Martin and Trost, Benjamin and Rasche, Daniel and G{\"u}ntner, Andreas and Doepper, Veronika and F{\"o}rster, Michael and K{\"o}hli, Markus and Angermann, Lisa and Antonoglou, Nikolaos and Zude, Manuela and Oswald, Sascha},
  title     = {Three years of soil moisture observations by a dense cosmic-ray neutron sensing cluster at an agricultural research site in north-east Germany},
  series = {Earth system science data : ESSD},
  volume    = {15},
  journal   = {Earth system science data : ESSD},
  number    = {7},
  publisher = {Copernics Publications},
  address   = {Katlenburg-Lindau},
  issn      = {1866-3508},
  doi       = {10.5194/essd-15-3243-2023},
  pages     = {3243 -- 3262},
  year      = {2023},
  abstract  = {Cosmic-ray neutron sensing (CRNS) allows for the estimation of root-zone soil water content (SWC) at the scale of several hectares. In this paper, we present the data recorded by a dense CRNS network operated from 2019 to 2022 at an agricultural research site in Marquardt, Germany - the first multi-year CRNS cluster. Consisting, at its core, of eight permanently installed CRNS sensors, the cluster was supplemented by a wealth of complementary measurements: data from seven additional temporary CRNS sensors, partly co-located with the permanent ones; 27 SWC profiles (mostly permanent); two groundwater observation wells; meteorological records; and Global Navigation Satellite System reflectometry (GNSS-R). Complementary to these continuous measurements, numerous campaign-based activities provided data by mobile CRNS roving, hyperspectral im-agery via UASs, intensive manual sampling of soil properties (SWC, bulk density, organic matter, texture, soil hydraulic properties), and observations of biomass and snow (cover, depth, and density). The unique temporal coverage of 3 years entails a broad spectrum of hydro-meteorological conditions, including exceptional drought periods and extreme rainfall but also episodes of snow coverage, as well as a dedicated irrigation experiment. Apart from serving to advance CRNS-related retrieval methods, this data set is expected to be useful for vari-ous disciplines, for example, soil and groundwater hydrology, agriculture, or remote sensing. Hence, we show exemplary features of the data set in order to highlight the potential for such subsequent studies. The data are available at doi.org/10.23728/b2share.551095325d74431881185fba1eb09c95 (Heistermann et al., 2022b).},
  language  = {en}
}
@phdthesis{Luna2023,
  author    = {Luna, Lisa Victoria},
  title     = {Rainfall-triggered landslides: conditions, prediction, and warning},
  doi       = {10.25932/publishup-60092},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-600927},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xix, 119},
  year      = {2023},
  abstract  = {Rainfall-triggered landslides are a globally occurring hazard that cause several thousand fatalities per year on average and lead to economic damages by destroying buildings and infrastructure and blocking transportation networks. For people living and governing in susceptible areas, knowing not only where, but also when landslides are most probable is key to inform strategies to reduce risk, requiring reliable assessments of weather-related landslide hazard and adequate warning. Taking proper action during high hazard periods, such as moving to higher levels of houses, closing roads and rail networks, and evacuating neighborhoods, can save lives. Nevertheless, many regions of the world with high landslide risk currently lack dedicated, operational landslide early warning systems. The mounting availability of temporal landslide inventory data in some regions has increasingly enabled data-driven approaches to estimate landslide hazard on the basis of rainfall conditions. In other areas, however, such data remains scarce, calling for appropriate statistical methods to estimate hazard with limited data. The overarching motivation for this dissertation is to further our ability to predict rainfall-triggered landslides in time in order to expand and improve warning. To this end, I applied Bayesian inference to probabilistically quantify and predict landslide activity as a function of rainfall conditions at spatial scales ranging from a small coastal town, to metropolitan areas worldwide, to a multi-state region, and temporal scales from hourly to seasonal. This thesis is composed of three studies. In the first study, I contributed to developing and validating statistical models for an online landslide warning dashboard for the small town of Sitka, Alaska, USA. We used logistic and Poisson regressions to estimate daily landslide probability and counts from an inventory of only five reported landslide events and 18 years of hourly precipitation measurements at the Sitka airport. Drawing on community input, we established two warning thresholds for implementation in the dashboard, which uses observed rainfall and US National Weather Service forecasts to provide real-time estimates of landslide hazard. In the second study, I estimated rainfall intensity-duration thresholds for shallow landsliding for 26 cities worldwide and a global threshold for urban landslides. I found that landslides in urban areas occurred at rainfall intensities that were lower than previously reported global thresholds, and that 31\% of urban landslides were triggered during moderate rainfall events. However, landslides in cities with widely varying climates and topographies were triggered above similar critical rainfall intensities: thresholds for 77\% of cities were indistinguishable from the global threshold, suggesting that urbanization may harmonize thresholds between cities, overprinting natural variability. I provide a baseline threshold that could be considered for warning in cities with limited landslide inventory data. In the third study, I investigated seasonal landslide response to annual precipitation patterns in the Pacific Northwest region, USA by using Bayesian multi-level models to combine data from five heterogeneous landslide inventories that cover different areas and time periods. I quantitatively confirmed a distinctly seasonal pattern of landsliding and found that peak landslide activity lags the annual precipitation peak. In February, at the height of the landslide season, landslide intensity for a given amount of monthly rainfall is up to ten times higher than at the season onset in November, underlining the importance of antecedent seasonal hillslope conditions. Together, these studies contributed actionable, objective information for landslide early warning and examples for the application of Bayesian methods to probabilistically quantify landslide hazard from inventory and rainfall data.},
  language  = {en}
}
@phdthesis{Han2023,
  author    = {Han, Sungju},
  title     = {Perceptions of nature-based solutions in the context of floods},
  doi       = {10.25932/publishup-57952},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-579524},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xiv, 150},
  year      = {2023},
  abstract  = {Traditional ways of reducing flood risk have encountered limitations in a climate-changing and rapidly urbanizing world. For instance, there has been a demanding requirement for massive investment in order to maintain a consistent level of security as well as increased flood exposure of people and property due to a false sense of security arising from the flood protection infrastructure. Against this background, nature-based solutions (NBS) have gained popularity as a sustainable and alternative way of dealing with diverse societal challenges such as climate change and biodiversity loss. In particular, their ability to reduce flood risks while also offering ecological benefits has recently received global attention. Diverse co-benefits of NBS that favor both humans and nature are viewed as promising a wide endorsement of NBS. However, people's perceptions of NBS are not always positive. Local resistance to NBS projects as well as decision-makers' and practitioners' unwillingness to adopt NBS have been pointed out as a bottleneck to the successful realization and mainstreaming of NBS. In this regard, there has been a growing necessity to investigate people's perceptions of NBS. Current research has lacked an integrative perspective of both attitudinal and contextual factors that guide perceptions of NBS; it not only lacks empirical evidence, but a few existing ones are rather conflicting without having underlying theories. This has led to the overarching research question of this dissertation, "What shapes people's perceptions of NBS in the context of flooding?" The dissertation aims to answer the following sub-questions in the three papers that make up this dissertation: 1. What are the topics reflected in the previous literature influencing perceptions of NBS as a means to reduce hydro-meteorological risks? (Paper I) 2. What are the stimulating and hampering attitudinal and contextual factors for mainstreaming NBS for flood risk management? How are NBS conceptualized? (Paper II) 3. How are public attitudes toward the NBS projects shaped? How do risk-and place-related factors shape individual attitudes toward NBS? (Paper III) This dissertation follows an integrative approach of considering "place" and "risk", as well as the surrounding context, by analyzing attitudinal (i.e., individual) and contextual (i.e., systemic) factors. "Place" is mainly concerned with affective elements (e.g., bond to locality and natural environment) whereas "risk" is related to cognitive elements (e.g., threat appraisal). The surrounding context provides systemic drivers and barriers with the possibility of interfering the influence of place and risk for perceptions of NBS. To empirically address the research questions, the current status of the knowledge about people's perceptions of NBS for flood risks was investigated by conducting a systematic review (Paper I). Based on these insights, a case study of South Korea was used to demonstrate key contextual and attitudinal factors for mainstreaming NBS through the lens of experts (Paper II). Lastly, by conducting a citizen survey, it investigated the relationship between the previously discussed concepts in Papers I and II using structural equation modeling, focusing on the core concepts, namely risk and place (Paper III). As a result, Paper I identified the key topics relating to people's perceptions, including the perceived value of co-benefits, perceived effectiveness of risk reduction effectiveness, participation of stakeholders, socio-economic and place-specific conditions, environmental attitude, and uncertainty of NBS. Paper II confirmed Paper I's findings regarding attitudinal factors. In addition, several contextual hampering or stimulating factors were found to be similar to those of any emerging technologies (i.e., path dependence, lack of operational and systemic capacity). Among all, one of the distinctive features in NBS contexts, at least in the South Korean case, is the politicization of NBS, which can lead to polarization of ideas and undermine the decision-making process. Finally, Paper III provides a framework with the core topics (i.e., place and risk) that were considered critical in Paper I and Paper II. This place-based risk appraisal model (PRAM) connects people at risk and places where hazards (i.e., floods) and interventions (i.e., NBS) take place. The empirical analysis shows that, among the place-related variables, nature bonding was a positive predictor of the perceived risk-reduction effectiveness of NBS, and place identity was a negative predictor of supportive attitude. Among the risk-related variables, threat appraisal had a negative effect on perceived risk reduction effectiveness and supportive attitude, while well-communicated information, trust in flood risk management, and perceived co-benefit were positive predictors. This dissertation proves that the place and risk attributes of NBS shape people's perceptions of NBS. In order to optimize the NBS implementation, it is necessary to consider the meanings and values held in place before project implementation and how these attributes interact with individual and/or community risk profiles and other contextual factors. With the increasing necessity of using NBS to lower flood risks, these results make important suggestions for the future NBS project strategy and NBS governance.},
  language  = {en}
}
@phdthesis{Riebold2023,
  author    = {Riebold, Johannes},
  title     = {On the linkage between future Arctic sea ice retreat, the large-scale atmospheric circulation and temperature extremes over Europe},
  doi       = {10.25932/publishup-60488},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-604883},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xi, 126},
  year      = {2023},
  abstract  = {Extreme weather and climate events are one of the greatest dangers for present-day society. Therefore, it is important to provide reliable statements on what changes in extreme events can be expected along with future global climate change. However, the projected overall response to future climate change is generally a result of a complex interplay between individual physical mechanisms originated within the different climate subsystems. Hence, a profound understanding of these individual contributions is required in order to provide meaningful assessments of future changes in extreme events. One aspect of climate change is the recently observed phenomenon of Arctic Amplification and the related dramatic Arctic sea ice decline, which is expected to continue over the next decades. The question to what extent Arctic sea ice loss is able to affect atmospheric dynamics and extreme events over mid-latitudes has received a lot of attention over recent years and still remains a highly debated topic. In this respect, the objective of this thesis is to contribute to a better understanding on the impact of future Arctic sea ice retreat on European temperature extremes and large-scale atmospheric dynamics. The outcomes are based on model data from the atmospheric general circulation model ECHAM6. Two different sea ice sensitivity simulations from the Polar Amplification Intercomparison Project are employed and contrasted to a present day reference experiment: one experiment with prescribed future sea ice loss over the entire Arctic, as well as another one with sea ice reductions only locally prescribed over the Barents-Kara Sea.\% prescribed over the entire Arctic, as well as only locally over the Barent/Karasea with a present day reference experiment. The first part of the thesis focuses on how future Arctic sea ice reductions affect large-scale atmospheric dynamics over the Northern Hemisphere in terms of occurrence frequency changes of five preferred Euro-Atlantic circulation regimes. When compared to circulation regimes computed from ERA5 it shows that ECHAM6 is able to realistically simulate the regime structures. Both ECHAM6 sea ice sensitivity experiments exhibit similar regime frequency changes. Consistent with tendencies found in ERA5, a more frequent occurrence of a Scandinavian blocking pattern in midwinter is for instance detected under future sea ice conditions in the sensitivity experiments. Changes in occurrence frequencies of circulation regimes in summer season are however barely detected. After identifying suitable regime storylines for the occurrence of European temperature extremes in winter, the previously detected regime frequency changes are used to quantify dynamically and thermodynamically driven contributions to sea ice-induced changes in European winter temperature extremes. It is for instance shown how the preferred occurrence of a Scandinavian blocking regime under low sea ice conditions dynamically contributes to more frequent midwinter cold extreme occurrences over Central Europe. In addition, a reduced occurrence frequency of a Atlantic trough regime is linked to reduced winter warm extremes over Mid-Europe. Furthermore, it is demonstrated how the overall thermodynamical warming effect due to sea ice loss can result in less (more) frequent winter cold (warm) extremes, and consequently counteracts the dynamically induced changes. Compared to winter season, circulation regimes in summer are less suitable as storylines for the occurrence of summer heat extremes. Therefore, an approach based on circulation analogues is employed in order to quantify thermodyamically and dynamically driven contributions to sea ice-induced changes of summer heat extremes over three different European sectors. Reduced occurrences of blockings over Western Russia are detected in the ECHAM6 sea ice sensitivity experiments; however, arguing for dynamically and thermodynamically induced contributions to changes in summer heat extremes remains rather challenging.},
  language  = {en}
}
@phdthesis{Kemper2023,
  author    = {Kemper, Tarek},
  title     = {KLIMAGRAR - Neue Methoden der Begleitforschung am Beispiel des klimagerechten Handelns in der Landwirtschaft},
  doi       = {10.25932/publishup-60192},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-601924},
  school      = {Universit{\"a}t Potsdam},
  pages     = {109},
  year      = {2023},
  abstract  = {In Forschungsprogrammen werden zahlreiche Akteure mit unterschiedlichen Hintergr{\"u}nden und fachlichen Expertisen in Einzel- oder Verbundvorhaben vereint, die jedoch weitestgehend unabh{\"a}ngig voneinander durchgef{\"u}hrt werden. Vor dem Hintergrund, dass gesamtgesellschaftliche Herausforderungen wie die globale Erw{\"a}rmung zunehmend disziplin{\"u}bergreifende L{\"o}sungsans{\"a}tze erfordern, sollten Vernetzungs- und Transferprozesse in Forschungsprogrammen st{\"a}rker in den Fokus r{\"u}cken. Mit der Implementierung einer Begleitforschung kann dieser Forderung Rechnung getragen werden. Begleitforschung unterscheidet sich in ihrer Herangehensweise und ihrer Zielvorstellung von den „{\"u}blichen" Projekten und kann in unterschiedlichen theoretischen Reinformen auftreten. Verk{\"u}rzt dargestellt agiert sie entweder (1) inhaltlich komplement{\"a}r zu den jeweiligen Forschungsprojekten, (2) auf einer Metaebene mit Fokus auf die Prozesse im Forschungsprogramm oder (3) als integrierende, synthetisierende Instanz, f{\"u}r die die Vernetzung der Projekte im Forschungsprogramm sowie der Wissenstransfer von Bedeutung sind. Zwar sind diese Formen analytisch in theoretische Reinformen trennbar, in der Praxis ergibt sich in der Regel jedoch ein Mix aus allen dreien. In diesem Zusammenhang schließt die vorliegende Dissertation als erg{\"a}nzende Studie an bisherige Ans{\"a}tze zum methodischen Handwerkszeug der Begleitforschung an und fokussiert auf folgende Fragestellungen: Auf welcher Basis kann die Vernetzung der Akteure in einem Forschungsprogramm durchgef{\"u}hrt werden, um diese effektiv zusammenzubringen? Welche weiteren methodischen Elemente sollten daran ansetzen, um einen Mehrwert zu generieren, der die Summe der Einzelergebnisse des Forschungsprogrammes {\"u}bersteigt? Von welcher Art kann dann ein solcher Mehrwert sein und welche Rolle spielt dabei die Begleitforschung? Das erste methodische Element bildet die Erhebung und Aufbereitung einer Ausgangsdatenbasis. Durch eine auf semantischer Analyse basierenden Verschlagwortung projektbezogener Texte l{\"a}sst sich eine umfassende Datenbasis aus den Inhalten der Forschungsprojekte generieren. Die Schlagw{\"o}rter werden dabei anhand eines kontrollierten Vokabulars in einem Schlagwortkatalog strukturiert. Parallel dazu werden sie wiederum den jeweiligen Projekten zugeordnet, wodurch diese thematische Merkmale erhalten. Um thematische {\"U}berschneidungen zwischen Forschungsprojekten sichtbar und interpretierbar zu machen, beinhaltet das zweite Element Ans{\"a}tze zur Visualisierung. Dazu werden die Informationen in einen Netzwerkgraphen transferiert, der sowohl alle im Forschungsprogramm involvierten Projekte als auch die identifizierten Schlagw{\"o}rter in Relation zueinander abbilden kann. So kann zum Beispiel sichtbar gemacht werden, welche Forschungsprojekte sich auf Basis ihrer Inhalte „n{\"a}her" sind als andere. Genau diese Information wird im dritten methodischen Element als Planungsgrundlage f{\"u}r unterschiedliche Veranstaltungsformate wie Arbeitstagungen oder Transferwerkst{\"a}tten genutzt. Das vierte methodische Element umfasst die Synthesebildung. Diese gestaltet sich als Prozess {\"u}ber den gesamten Zeitraum der Zusammenarbeit zwischen Begleitforschung und den weiteren Forschungsprojekten hinweg, da in die Synthese unter anderem Zwischen-, Teil- und Endergebnisse der Projekte einfließen, genauso wie Inhalte aus den unterschiedlichen Veranstaltungen. Letztendlich ist dieses vierte Element auch das Mittel, um aus den integrierten und synthetisierten Informationen Handlungsempfehlungen f{\"u}r zuk{\"u}nftige Vorhaben abzuleiten. Die Erarbeitung der methodischen Elemente erfolgte im laufenden Prozess des Begleitforschungsprojektes KlimAgrar, welches der vorliegenden Dissertation als Fallbeispiel dient und dessen Hintergr{\"u}nde in der Thematik Klimaschutz und Klimaanpassung in der Landwirtschaft im Text ausf{\"u}hrlich erl{\"a}utert werden.},
  language  = {de}
}
@phdthesis{Duy2023,
  author    = {Duy, Nguyen Le},
  title     = {Hydrological processes in the Vietnamese Mekong Delta},
  doi       = {10.25932/publishup-60260},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-602607},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xxi, 153},
  year      = {2023},
  abstract  = {Understanding hydrological processes is of fundamental importance for the Vietnamese national food security and the livelihood of the population in the Vietnamese Mekong Delta (VMD). As a consequence of sparse data in this region, however, hydrologic processes, such as the controlling processes of precipitation, the interaction between surface and groundwater, and groundwater dynamics, have not been thoroughly studied. The lack of this knowledge may negatively impact the long-term strategic planning for sustainable groundwater resources management and may result in insufficient groundwater recharge and freshwater scarcity. It is essential to develop useful methods for a better understanding of hydrological processes in such data-sparse regions. The goal of this dissertation is to advance methodologies that can improve the understanding of fundamental hydrological processes in the VMD, based on the analyses of stable water isotopes and monitoring data. The thesis mainly focuses on the controlling processes of precipitation, the mechanism of surface-groundwater interaction, and the groundwater dynamics. These processes have not been fully addressed in the VMD so far. The thesis is based on statistical analyses of the isotopic data of Global Network of Isotopes in Precipitation (GNIP), of meteorological and hydrological data from Vietnamese agencies, and of the stable water isotopes and monitoring data collected as part of this work. First, the controlling processes of precipitation were quantified by the combination of trajectory analysis, multi-factor linear regression, and relative importance analysis (hereafter, a model-based statistical approach). The validity of this approach is confirmed by similar, but mainly qualitative results obtained in other studies. The total variation in precipitation isotopes (δ18O and δ2H) can be better explained by multiple linear regression (up to 80\%) than single-factor linear regression (30\%). The relative importance analysis indicates that atmospheric moisture regimes control precipitation isotopes rather than local climatic conditions. The most crucial factor is the upstream rainfall along the trajectories of air mass movement. However, the influences of regional and local climatic factors vary in importance over the seasons. The developed model-based statistical approach is a robust tool for the interpretation of precipitation isotopes and could also be applied to understand the controlling processes of precipitation in other regions. Second, the concept of the two-component lumped-parameter model (LPM) in conjunction with stable water isotopes was applied to examine the surface-groundwater interaction in the VMD. A calibration framework was also set up to evaluate the behaviour, parameter identifiability, and uncertainties of two-component LPMs. The modelling results provided insights on the subsurface flow conditions, the recharge contributions, and the spatial variation of groundwater transit time. The subsurface flow conditions at the study site can be best represented by the linear-piston flow distribution. The contributions of the recharge sources change with distance to the river. The mean transit time (mTT) of riverbank infiltration increases with the length of the horizontal flow path and the decreasing gradient between river and groundwater. River water infiltrates horizontally mainly via the highly permeable aquifer, resulting in short mTTs (<40 weeks) for locations close to the river (<200 m). The vertical infiltration from precipitation takes place primarily via a low-permeable overlying aquitard, resulting in considerably longer mTTs (>80 weeks). Notably, the transit time of precipitation infiltration is independent of the distance to the river. All these results are hydrologically plausible and could be quantified by the presented method for the first time. This study indicates that the highly complex mechanism of surface-groundwater interaction at riverbank infiltration systems can be conceptualized by exploiting two-component LPMs. It is illustrated that the model concept can be used as a tool to investigate the hydrological functioning of mixing processes and the flow path of multiple water components in riverbank infiltration systems. Lastly, a suite of time series analysis approaches was applied to examine the groundwater dynamics in the VMD. The assessment was focused on the time-variant trends of groundwater levels (GWLs), the groundwater memory effect (representing the time that an aquifer holds water), and the hydraulic response between surface water and multi-layer alluvial aquifers. The analysis indicates that the aquifers act as low-pass filters to reduce the high-frequency signals in the GWL variations, and limit the recharge to the deep groundwater. The groundwater abstraction has exceeded groundwater recharge between 1997 and 2017, leading to the decline of groundwater levels (0.01-0.55 m/year) in all considered aquifers in the VMD. The memory effect varies according to the geographical location, being shorter in shallow aquifers and flood-prone areas and longer in deep aquifers and coastal regions. Groundwater depth, season, and location primarily control the variation of the response time between the river and alluvial aquifers. These findings are important contributions to the hydrogeological literature of a little-known groundwater system in an alluvial setting. It is suggested that time series analysis can be used as an efficient tool to understand groundwater systems where resources are insufficient to develop a physical-based groundwater model. This doctoral thesis demonstrates that important aspects of hydrological processes can be understood by statistical analysis of stable water isotope and monitoring data. The approaches developed in this thesis can be easily transferred to regions in similar tropical environments, particularly those in alluvial settings. The results of the thesis can be used as a baseline for future isotope-based studies and contribute to the hydrogeological literature of little-known groundwater systems in the VMD.},
  language  = {en}
}
@phdthesis{Serwene2023,
  author    = {Serwene, Pola},
  title     = {Geographie verstehen durch Zweisprachigkeit},
  series = {Potsdamer Geographische Praxis},
  journal   = {Potsdamer Geographische Praxis},
  number    = {19},
  publisher = {Universit{\"a}tsverlag Potsdam},
  address   = {Potsdam},
  isbn      = {978-3-86956-557-6},
  issn      = {2194-1599},
  doi       = {10.25932/publishup-57848},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-578486},
  school      = {Universit{\"a}t Potsdam},
  pages     = {360},
  year      = {2023},
  abstract  = {Bilingualer Unterricht gilt als das Erfolgsmodell f{\"u}r den schulischen Fremdsprachenerwerb in Deutschland und die Beherrschung einer Fremdsprache in Wort und Schrift ist eine entscheidende berufsqualifizierende Kompetenz in unserer globalisierten Welt. Insbesondere die Verzahnung fachlicher und sprachlicher Inhalte im Kontext Bilingualen Unterrichts scheint gewinnbringend f{\"u}r den Fremdspracherwerb zu sein. Dabei ist die Diskrepanz zwischen den zumeist noch geringen fremdsprachlichen F{\"a}higkeiten der Lernenden und den fachlichen Anspr{\"u}chen des Geographieunterrichts eine große Herausforderung f{\"u}r fachliches Lernen im bilingualen Sachfachunterricht. Es stellt sich die Frage, wie der Bilinguale Unterricht gestaltet sein muss, um einerseits geographische Themen fachlich komplex behandeln zu k{\"o}nnen und andererseits die Lernenden fremdsprachlich nicht zu {\"u}berfordern. Im Rahmen einer Design-Based-Research-Studie im bilingualen Geographieunterricht wurde untersucht, wie fachliches Lernen im bilingualen Geographieunterricht durch den Einsatz beider beteiligter Sprachen (Englisch/Deutsch) gef{\"o}rdert werden kann. Auf Grundlage eines theoretisch fundierten Kenntnisstands zum Bilingualen Unterricht und zum Lernen mit Fachkonzepten im Geographieunterricht wurde eine Lernumgebung konzipiert, im Unterricht erprobt und weiterentwickelt, in der Strategien des Sprachwechsels zum Einsatz kommen. Die Ergebnisse der Studie sind kontextbezogene Theorien einer zweisprachigen Didaktik f{\"u}r den bilingualen Geographieunterricht und Erkenntnisse zum Lernen mit Fachkonzepten im Geographieunterricht am Beispiel des geographischen Konzepts Wandel. Produkt der Studie ist eine unterrichtstaugliche Lernumgebung zum Thema Wandlungsprozesse an ausgew{\"a}hlten Orten f{\"u}r den bilingualen Geographieunterricht mit didaktischem Konzept, Unterrichtsmaterialien und -medien.},
  language  = {de}
}
@phdthesis{Zhang2023,
  author    = {Zhang, Xiaolin},
  title     = {Evaluation of nitrogen dynamics in high-order streams and rivers based on high-frequency monitoring},
  doi       = {10.25932/publishup-60764},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-607642},
  school      = {Universit{\"a}t Potsdam},
  pages     = {X, 113},
  year      = {2023},
  abstract  = {Nutrient storage, transform and transport are important processes for achieving environmental and ecological health, as well as conducting water management plans. Nitrogen is one of the most noticeable elements due to its impacts on tremendous consequences of eutrophication in aquatic systems. Among all nitrogen components, researches on nitrate are blooming because of widespread deployments of in-situ high-frequency sensors. Monitoring and studying nitrate can become a paradigm for any other reactive substances that may damage environmental conditions and cause economic losses. Identifying nitrate storage and its transport within a catchment are inspiring to the management of agricultural activities and municipal planning. Storm events are periods when hydrological dynamics activate the exchange between nitrate storage and flow pathways. In this dissertation, long-term high-frequency monitoring data at three gauging stations in the Selke river were used to quantify event-scale nitrate concentration-discharge (C-Q) hysteretic relationships. The Selke catchment is characterized into three nested subcatchments by heterogeneous physiographic conditions and land use. With quantified hysteresis indices, impacts of seasonality and landscape gradients on C-Q relationships are explored. For example, arable area has deep nitrate legacy and can be activated with high intensity precipitation during wetting/wet periods (i.e., the strong hydrological connectivity). Hence, specific shapes of C-Q relationships in river networks can identify targeted locations and periods for agricultural management actions within the catchment to decrease nitrate output into downstream aquatic systems like the ocean. The capacity of streams for removing nitrate is of both scientific and social interest, which makes the quantification motivated. Although measurements of nitrate dynamics are advanced compared to other substances, the methodology to directly quantify nitrate uptake pathways is still limited spatiotemporally. The major problem is the complex convolution of hydrological and biogeochemical processes, which limits in-situ measurements (e.g., isotope addition) usually to small streams with steady flow conditions. This makes the extrapolation of nitrate dynamics to large streams highly uncertain. Hence, understanding of in-stream nitrate dynamic in large rivers is still necessary. High-frequency monitoring of nitrate mass balance between upstream and downstream measurement sites can quantitatively disentangle multi-path nitrate uptake dynamics at the reach scale (3-8 km). In this dissertation, we conducted this approach in large stream reaches with varying hydro-morphological and environmental conditions for several periods, confirming its success in disentangling nitrate uptake pathways and their temporal dynamics. Net nitrate uptake, autotrophic assimilation and heterotrophic uptake were disentangled, as well as their various diel and seasonal patterns. Natural streams generally can remove more nitrate under similar environmental conditions and heterotrophic uptake becomes dominant during post-wet seasons. Such two-station monitoring provided novel insights into reach-scale nitrate uptake processes in large streams. Long-term in-stream nitrate dynamics can also be evaluated with the application of water quality model. This is among the first time to use a data-model fusion approach to upscale the two-station methodology in large-streams with complex flow dynamics under long-term high-frequency monitoring, assessing the in-stream nitrate retention and its responses to drought disturbances from seasonal to sub-daily scale. Nitrate retention (both net uptake and net release) exhibited substantial seasonality, which also differed in the investigated normal and drought years. In the normal years, winter and early spring seasons exhibited extensive net releases, then general net uptake occurred after the annual high-flow season at later spring and early summer with autotrophic processes dominating and during later summer-autumn low-flow periods with heterotrophy-characteristics predominating. Net nitrate release occurred since late autumn until the next early spring. In the drought years, the late-autumn net releases were not so consistently persisted as in the normal years and the predominance of autotrophic processes occurred across seasons. Aforementioned comprehensive results of nitrate dynamics on stream scale facilitate the understanding of instream processes, as well as raise the importance of scientific monitoring schemes for hydrology and water quality parameters.},
  language  = {en}
}
@phdthesis{Schoppa2023,
  author    = {Schoppa, Lukas},
  title     = {Dynamics in the flood vulnerability of companies},
  doi       = {10.25932/publishup-59242},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-592424},
  school      = {Universit{\"a}t Potsdam},
  pages     = {X, 165},
  year      = {2023},
  abstract  = {River flooding is a constant peril for societies, causing direct economic losses in the order of \$100 billion worldwide each year. Under global change, the prolonged concentration of people and assets in floodplains is accompanied by an emerging intensification of flood extremes due to anthropogenic global warming, ultimately exacerbating flood risk in many regions of the world. Flood adaptation plays a key role in the mitigation of impacts, but poor understanding of vulnerability and its dynamics limits the validity of predominant risk assessment methods and impedes effective adaptation strategies. Therefore, this thesis investigates new methods for flood risk assessment that embrace the complexity of flood vulnerability, using the understudied commercial sector as an application example. Despite its importance for accurate risk evaluation, flood loss modeling has been based on univariable and deterministic stage-damage functions for a long time. However, such simplistic methods only insufficiently describe the large variation in damage processes, which initiated the development of multivariable and probabilistic loss estimation techniques. The first study of this thesis developed flood loss models for companies that are based on emerging statistical and machine learning approaches (i.e., random forest, Bayesian network, Bayesian regression). In a benchmarking experiment on basis of object-level loss survey data, the study showed that all proposed models reproduced the heterogeneity in damage processes and outperformed conventional stage-damage functions with respect to predictive accuracy. Another advantage of the novel methods is that they convey probabilistic information in predictions, which communicates the large remaining uncertainties transparently and, hence, supports well-informed risk assessment. Flood risk assessment combines vulnerability assessment (e.g., loss estimation) with hazard and exposure analyses. Although all of the three risk drivers interact and change over time, such dependencies and dynamics are usually not explicitly included in flood risk models. Recently, systemic risk assessment that dissolves the isolated consideration of risk drivers has gained traction, but the move to holistic risk assessment comes with limited thoroughness in terms of loss estimation and data limitations. In the second study, I augmented a socio-hydrological system dynamics model for companies in Dresden, Germany, with the multivariable Bayesian regression loss model from the first study. The additional process-detail and calibration data improved the loss estimation in the systemic risk assessment framework and contributed to more accurate and reliable simulations. The model uses Bayesian inference to quantify uncertainty and learn the model parameters from a combination of prior knowledge and diverse data. The third study demonstrates the potential of the socio-hydrological flood risk model for continuous, long-term risk assessment and management. Using hydroclimatic ad socioeconomic forcing data, I projected a wide range of possible risk trajectories until the end of the century, taking into account the adaptive behavior of companies. The study results underline the necessity of increased adaptation efforts to counteract the expected intensification of flood risk due to climate change. A sensitivity analysis of the effectiveness of different adaptation measures and strategies revealed that optimized adaptation has the potential to mitigate flood risk by up to 60\%, particularly when combining structural and non-structural measures. Additionally, the application shows that systemic risk assessment is capable of capturing adverse long-term feedbacks in the human-flood system such as the levee effect. Overall, this thesis advances the representation of vulnerability in flood risk modeling by offering modeling solutions that embrace the complexity of human-flood interactions and quantify uncertainties consistently using probabilistic modeling. The studies show how scarce information in data and previous experiments can be integrated in the inference process to provide model predictions and simulations that are reliable and rich in information. Finally, the focus on the flood vulnerability of companies provides new insights into the heterogeneous damage processes and distinct flood coping of this sector.},
  language  = {en}
}
@article{ArguellodeSouzaSamprognaMohorGuzmanAriasetal.2023,
  author    = {Arguello de Souza, Felipe Augusto and Samprogna Mohor, Guilherme and Guzman Arias, Diego Alejandro and Sarmento Buarque, Ana Carolina and Taffarello, Denise and Mendiondo, Eduardo Mario},
  title     = {Droughts in S{\~a}o Paulo},
  series = {Urban water journal},
  volume    = {20},
  journal   = {Urban water journal},
  number    = {10},
  publisher = {Taylor \& Francis},
  address   = {London [u.a.]},
  issn      = {1573-062X},
  doi       = {10.1080/1573062X.2022.2047735},
  pages     = {1682 -- 1694},
  year      = {2023},
  abstract  = {Literature has suggested that droughts and societies are mutually shaped and, therefore, both require a better understanding of their coevolution on risk reduction and water adaptation. Although the Sao Paulo Metropolitan Region drew attention because of the 2013-2015 drought, this was not the first event. This paper revisits this event and the 1985-1986 drought to compare the evolution of drought risk management aspects. Documents and hydrological records are analyzed to evaluate the hazard intensity, preparedness, exposure, vulnerability, responses, and mitigation aspects of both events. Although the hazard intensity and exposure of the latter event were larger than the former one, the policy implementation delay and the dependency of service areas in a single reservoir exposed the region to higher vulnerability. In addition to the structural and non-structural tools implemented just after the events, this work raises the possibility of rainwater reuse for reducing the stress in reservoirs.},
  language  = {en}
}
@article{RodriguesRodriguesRaabeetal.2023,
  author    = {Rodrigues, Glauber Pontes and Rodrigues, {\´I}talo Sampaio and Raabe, Armin and Holstein, Peter and De Araujo, Jos{\`e} Carlos},
  title     = {Direct measurement of open-water evaporation},
  series = {Hydrological sciences journal},
  volume    = {68},
  journal   = {Hydrological sciences journal},
  number    = {3},
  publisher = {Taylor \& Francis},
  address   = {Abingdon, Oxon},
  issn      = {0262-6667},
  doi       = {10.1080/02626667.2022.2157278},
  pages     = {379 -- 394},
  year      = {2023},
  abstract  = {This study investigates the sensitivity and uncertainty of evaporation assessment in a tropical reservoir in northeastern Brazil. For this purpose, four approaches were used: Penman, a Dalton-modified equation, a pressure meter and a novel acoustic sensor. The main objective is to evaluate whether sensors can be employed to adequately assess lake evaporation. The sensors were installed in floating pans and the equations are based on variables collected from a raft. The wind-inducted waves in the reservoir often disturbed the measurements using both pressure (uncertainty of +/- 0.6 mm) and acoustic (uncertainty of +/- 0.1 mm) sensors, causing flaws and affecting continuous monitoring. The modified Dalton model, based on data collected with a floating station, estimated values over three-hour courses of evaporation similar to those measured by the pressure meter. These findings are important contributions to an accurate monitoring of water losses through evaporation and reservoir operation, particularly in dry regions.},
  language  = {en}
}
@phdthesis{Calitri2023,
  author    = {Calitri, Francesca},
  title     = {Co-evolution of erosion rates, weathering and profile development in soil landscapes of hummocky ground moraines},
  doi       = {10.25932/publishup-60138},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-601387},
  school      = {Universit{\"a}t Potsdam},
  pages     = {XXVII, 163, V},
  year      = {2023},
  abstract  = {Soil is today considered a non-renewable resource on societal time scale, as the rate of soil loss is higher than the one of soil formation. Soil formation is complex, can take several thousands of years and is influenced by a variety of factors, one of them is time. Oftentimes, there is the assumption of constant and progressive conditions for soil and/or profile development (i.e., steady-state). In reality, for most of the soils, their (co-)evolution leads to a complex and irregular soil development in time and space characterised by "progressive" and "regressive" phases. Lateral transport of soil material (i.e., soil erosion) is one of the principal processes shaping the land surface and soil profile during "regressive" phases and one of the major environmental problems the world faces. Anthropogenic activities like agriculture can exacerbate soil erosion. Thus, it is of vital importance to distinguish short-term soil redistribution rates (i.e., within decades) influenced by human activities differ from long-term natural rates. To do so, soil erosion (and denudation) rates can be determined by using a set of isotope methods that cover different time scales at landscape level. With the aim to unravel the co-evolution of weathering, soil profile development and lateral redistribution on a landscape level, we used Pluthonium-239+240 (239+240Pu), Beryllium-10 (10Be, in situ and meteoric) and Radiocarbon (14C) to calculate short- and long-term erosion rates in two settings, i.e., a natural and an anthropogenic environment in the hummocky ground moraine landscape of the Uckermark, North-eastern Germany. The main research questions were: 1. How do long-term and short-term rates of soil redistributing processes differ? 2. Are rates calculated from in situ 10Be comparable to those of using meteoric 10Be? 3. How do soil redistribution rates (short- and long-term) in an agricultural and in a natural landscape compare to each other? 4. Are the soil patterns observed in northern Germany purely a result of past events (natural and/or anthropogenic) or are they imbedded in ongoing processes? Erosion and deposition are reflected in a catena of soil profiles with no or almost no erosion on flat positions (hilltop), strong erosion on the mid-slope and accumulation of soil material at the toeslope position. These three characteristic process domains were chosen within the CarboZALF-D experimental site, characterised by intense anthropogenic activities. Likewise, a hydrosequence in an ancient forest was chosen for this study and being regarded as a catena strongly influenced by natural soil transport. The following main results were obtained using the above-mentioned range of isotope methods available to measure soil redistribution rates depending on the time scale needed (e.g., 239+240Pu, 10Be, 14C): 1. Short-term erosion rates are one order of magnitude higher than long-term rates in agricultural settings. 2. Both meteoric and in situ 10Be are suitable soil tracers to measure the long-term soil redistribution rates giving similar results in an anthropogenic environment for different landscape positions (e.g., hilltop, mid-slope, toeslope) 3. Short-term rates were extremely low/negligible in a natural landscape and very high in an agricultural landscape - -0.01 t ha-1 yr-1 (average value) and -25 t ha-1 yr-1 respectively. On the contrary, long-term rates in the forested landscape are comparable to those calculated in the agricultural area investigated with average values of -1.00 t ha-1 yr-1 and -0.79 t ha-1 yr-1. 4. Soil patterns observed in the forest might be due to human impact and activities started after the first settlements in the region, earlier than previously postulated, between 4.5 and 6.8 kyr BP, and not a result of recent soil erosion. 5. Furthermore, long-term soil redistribution rates are similar independently from the settings, meaning past natural soil mass redistribution processes still overshadow the present anthropogenic erosion processes. Overall, this study could make important contributions to the deciphering of the co-evolution of weathering, soil profile development and lateral redistribution in North-eastern Germany. The multi-methodological approach used can be challenged by the application in a wider range of landscapes and geographic regions.},
  language  = {en}
}
@phdthesis{Mtilatila2023,
  author    = {Mtilatila, Lucy Mphatso Ng'ombe},
  title     = {Climate change effects on drought, freshwater availability and hydro-power generation in an African environment},
  doi       = {10.25932/publishup-59929},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-599298},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xv, 167},
  year      = {2023},
  abstract  = {The work is designed to investigate the impacts and sensitivity of climate change on water resources, droughts and hydropower production in Malawi, the South-Eastern region which is highly vulnerable to climate change. It is observed that rainfall is decreasing and temperature is increasing which calls for the understanding of what these changes may impact the water resources, drought occurrences and hydropower generation in the region. The study is conducted in the Greater Lake Malawi Basin (Lake Malawi and Shire River Basins) and is divided into three projects. The first study is assessing the variability and trends of both meteorological and hydrological droughts from 1970-2013 in Lake Malawi and Shire River basins using the standardized precipitation index (SPI) and standardized precipitation and evaporation Index (SPEI) for meteorological droughts and the lake level change index (LLCI) for hydrological droughts. And later the relationship of the meteorological and hydrological droughts is established. While the second study extends the drought analysis into the future by examining the potential future meteorological water balance and associated drought characteristics such as the drought intensity (DI), drought months (DM), and drought events (DE) in the Greater Lake Malawi Basin. The sensitivity of drought to changes of rainfall and temperature is also assessed using the scenario-neutral approach. The climate change projections from 20 Coordinated Regional Climate Downscaling Experiment (CORDEX) models for Africa based on two scenarios (RCP4.5 and RCP8.5) for the periods 2021-2050 and 2071-2100 are used. The study also investigates the effect of bias-correction (i.e., empirical quantile mapping) on the ability of the climate model ensemble in reproducing observed drought characteristics as compared to raw climate projections. The sensitivity of key hydrologic variables and hydropower generation to climate change in Lake Malawi and Shire River basins is assessed in third study. The study adapts the mesoscale Hydrological Model (mHM) which is applied separately in the Upper Lake Malawi and Shire River basins. A particular Lake Malawi model, which focuses on reservoir routing and lake water balance, has been developed and is interlinked between the two basins. Similar to second study, the scenario-neutral approach is also applied to determine the sensitivity of climate change on water resources more particularly Lake Malawi level and Shire River flow which later helps to estimate the hydropower production susceptibility. Results suggest that meteorological droughts are increasing due to a decrease in precipitation which is exacerbated by an increase in temperature (potential evapotranspiration). The hydrological system of Lake Malawi seems to have a >24-month memory towards meteorological conditions since the 36-months SPEI can predict hydrological droughts ten-months in advance. The study has found the critical lake level that would trigger hydrological drought to be 474.1 m.a.s.l. Despite the differences in the internal structures and uncertainties that exist among the climate models, they all agree on an increase of meteorological droughts in the future in terms of higher DI and longer events (DM). DI is projected to increase between +25\% and +50\% during 2021-2050 and between +131\% and +388\% during 2071-2100. This translates into +3 to +5, and +7 to +8 more drought months per year during both periods, respectively. With longer lasting drought events, DE is decreasing. Projected droughts based on RCP8.5 are 1.7 times more severe than droughts based on RCP4.5. It is also found that an annual temperature increase of 1°C decreases mean lake level and outflow by 0.3 m and 17\%, respectively, signifying the importance of intensified evaporation for Lake Malawi's water budget. Meanwhile, a +5\% (-5\%) deviation in annual rainfall changes mean lake level by +0.7 m (-0.6 m). The combined effects of temperature increase and rainfall decrease result in significantly lower flows on Shire River. The hydrological river regime may change from perennial to seasonal with the combination of annual temperature increase and precipitation decrease beyond 1.5°C (3.5°C) and -20\% (-15\%). The study further projects a reduction in annual hydropower production between 1\% (RCP8.5) and 2.5\% (RCP4.5) during 2021-2050 and between 5\% (RCP4.5) and 24\% (RCP8.5) during 2071-2100. The findings are later linked to global policies more particularly the United Nations Framework Convention on Climate Change (UNFCCC)'s Paris Agreement and the United Nations (UN)'s Sustainable Development Goals (SDGs), and how the failure to adhere the restriction of temperature increase below the global limit of 1.5°C will affect drought and the water resources in Malawi consequently impact the hydropower production. As a result, the achievement of most of the SDGs will be compromised. The results show that it is of great importance that a further development of hydro energy on the Shire River should take into account the effects of climate change. The information generation is important for decision making more especially supporting the climate action required to fight against climate change. The frequency of extreme climate events due to climate change has reached the climate emergency as saving lives and livelihoods require urgent action.},
  language  = {en}
}
@phdthesis{Nomosatryo2023,
  author    = {Nomosatryo, Sulung},
  title     = {Biogeochemical characteristics of a tropical lake},
  doi       = {10.25932/publishup-59400},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-594006},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xix, 175},
  year      = {2023},
  abstract  = {Biogeochemical analyses of lacustrine environments are well-established methods that allow exploring and understanding complex systems in the lake ecosystem. However, most were conducted in temperate lakes controlled by entirely different physical conditions than in tropical climates. The most important difference between the temperate and tropical lakes is lacking seasonal temperature fluctuations in the latter, which leads to a stable temperature gradient in the water column. Thus, the water column in tropical latitudes generally is void of perturbations that can be seen in their temperate counterparts. Permanent stratification in the water column provides optimal conditions for intact sedimentation. The geochemical processes in the water column and the weathering process in the distinct lithology in the catchment leads to the different biogeochemical characteristic in the sediment. Conducting a biogeochemical study in this lake sediment, especially in the Sediment Water Interface (SWI) helps reveal the sedimentation and diagenetic process records influenced by the internal or external loading. Lake Sentani, the study area, is one of the thousands of lakes in Indonesia and located in the Papua province. This tropical lake has a unique feature, as it consists of four interconnected sub-basins with different water depths. More importantly, its catchment is comprised of various different lithologies. Hence, its lithological characteristics are highly diverse, and range from mafic and ultramafic rocks to clastic sediment and carbonates. Each sub-basin receives a distinct sediment input. Equally important, besides the natural loading, Lake Sentani is also influenced by anthropogenic input. Previous studies have elaborated that there is an increase in population growth rate around the lake which has direct consequences on eutrophication. Considering these factors, the government of The Republic of Indonesia put Lake Sentani on the list of national priority lakes for restoration. This thesis aims to develop a fundamental understanding of Lake Sentani's sedimentary geochemistry and geomicrobiology with a special focus on the effects of different lithologies and anthropogenic pressures in the catchment area. We conducted geochemical and geomicrobiology research on Lake Sentani to meet this objective. We investigated geochemical characteristics in the water column, porewater, and sediment core of the four sub-basins. Additional to direct investigations of the lake itself, we also studied the sediments in the tributary rivers, of which some are ephemeral, as well as the river mouths, as connections between riverine and the lacustrine habitat. The thesis is composed of three main publications about Lake Sentani and supported by several publications that focus on other tropical lakes in Indonesia. The first main publication investigates the geochemical characterization of the water column, porewater, and surface sediment (upper 40-50 cm) from the center of the four sub-basins. It reveals that besides catchment lithology, the water column heavily influences the geochemical characteristics in the lake sediments and their porewater. The findings indicate that water column stratification has a strong influence on overall chemistry. The four sub-basins are very different with regard to their water column chemistry. Based on the physicochemical profiles, especially dissolved oxygen, one sub-basin is oxygenated, one intermediate i.e. just reaches oxygen depletion at the sediment-water interface, and two sub-basins are fully meromictic. However, all four sub-basins share the same surface water chemistry. The structure of the water column creates differences on the patterns of anions and cations in the porewater. Likewise, the distinct differences in geochemical composition between the sub-basins show that the lithology in the catchment affects the geochemical characteristic in the sediment. Overall, water column stratification and particularly bottom water oxygenation strongly influence the overall elemental composition of the sediment and porewater composition. The second publication reveals differences in surface sediment composition between habitats, influenced by lithological variations in the catchment area. The macro-element distribution shows that the geochemical characteristics between habitats are different. Furthermore, the geochemical composition also indicates a distinct distribution between the sub-basins. The geochemical composition of the eastern sub-basin suggests that lithogenic elements are more dominant than authigenic elements. This is also supported by sulfide speciation, particle distribution, and smear slide data. The third publication is a geomicrobiological study of the surface sediment. We compare the geochemical composition of the surface sediment and its microbiological composition and compare the different signals. Next Generation Sequencing (NGS) of the 16S rRNA gene was applied to determine the microbial community composition of the surface sediment from a great number of locations. We use a large number of sampling sites in all four sub-basins as well as in the rivers and river mouths to illustrate the links between the river, the river mouth, and the lake. Rigorous assessment of microbial communities across the diverse Lake Sentani habitats allowed us to study some of these links and report novel findings on microbial patterns in such ecosystems. The main result of the Principal Coordinates Analysis (PCoA) based on microbial community composition highlighted some commonalities but also differences between the microbial community analysis and the geochemical data. The microbial community in rivers, river mouths and sub-basins is strongly influenced by anthropogenic input from the catchment area. Generally, Bacteroidetes and Firmicutes could be an indicator for river sediments. The microbial community in the river is directly influenced by anthropogenic pressure and is markedly different from the lake sediment. Meanwhile, the microbial community in the lake sediment reflects the anoxic environment, which is prevalent across the lake in all sediments below a few mm burial depth. The lake sediments harbour abundant sulfate reducers and methanogens. The microbial communities in sediments from river mouths are influenced by both rivers and lake ecosystems. This study provides valuable information to understand the basic processes that control biogeochemical cycling in Lake Sentani. Our findings are critical for lake managers to accurately assess the uncertainties of the changing environmental conditions related to the anthropogenic pressure in the catchment area. Lake Sentani is a unique study site directly influenced by the different geology across the watershed and morphometry of the four studied basins. As a result of these factors, there are distinct geochemical differences between the habitats (river, river mouth, lake) and the four sub-basins. In addition to geochemistry, microbial community composition also shows differences between habitats, although there are no obvious differences between the four sub-basins. However, unlike sediment geochemistry, microbial community composition is impacted by human activities. Therefore, this thesis will provide crucial baseline data for future lake management.},
  language  = {en}
}