@inproceedings{MaurerCaviedesVoulliemeHinzetal., author = {Maurer, Thomas and Caviedes-Voulli{\`e}me, Daniel and Hinz, Christoph and Gerke, Horst H.}, title = {Dynamik der initialen ({\"o}ko-) hydrologischen Entwicklung - Modellierung von Anfangsbedingungen und Wasserfl{\"u}ssen in einem exemplarischen Einzugsgebiet}, series = {Abstract-Sammlung zu Posterbeitr{\"a}gen, eingereicht zum Tag der Hydrologie in Trier 2017, 23. 03. - 24. 03. 2017}, booktitle = {Abstract-Sammlung zu Posterbeitr{\"a}gen, eingereicht zum Tag der Hydrologie in Trier 2017, 23. 03. - 24. 03. 2017}, pages = {S. 20}, language = {de} } @inproceedings{MaurerPohleOeseretal., author = {Maurer, Thomas and Pohle, Ina and Oeser, Anne and Sieber, Andr{\´e} and Hinz, Christoph}, title = {Investigating the interrelations between throughfall, meteorological variables and vegetation structure in a developing hydrological catchment}, series = {European Geosciences Union General Assembly 2017 Vienna, Austria, 23-28 April 2017}, booktitle = {European Geosciences Union General Assembly 2017 Vienna, Austria, 23-28 April 2017}, publisher = {European Geophysical Society}, address = {Katlenburg-Lindau}, abstract = {In landscapes with heterogeneous vegetation structure, interception and throughfall patterns produce spatiotemporal variability of soil moisture. This variability is important for eco-hydrological processes, in particular on small spatial scales up to the catchment scale. Throughfall depends on vegetation structure, whereas vegetation development is presumably co-determined by the spatio-temporal distribution of throughfall itself. In addition to vegetation structure, meteorological factors like wind speed and rainfall intensity also have an impact on throughfall. The objective of this study is to quantify the influence of vegetation structure and meteorological variables on spatial (and in the long run the temporal) variability of throughfall. For that purpose, we developed an approach combining field methods, image analysis and multivariate statistics. The 6-ha constructed catchment ‚H{\"u}hnerwasser' (aka Chicken Creek, southern Brandenburg, Germany) offers ideal conditions for the investigation of eco-hydrological feedback processes. After more than 10 years of development, vegetation structure on the catchment is spatially heterogeneous and evolves through natural succession. Furthermore, complementary meteorological data are available on-site. Throughfall was measured using 50 tipping-bucket rain gauges, which are aligned along two transects in 0.5 and 1 m heights, covering the dominating vegetation types on the catchment (e.g., robinia, sallow thorn, reed, reedgrass, herbs). The spatial distribution of vegetation structures around each measurement site was recorded with hemispheric photographs, which were subsequently analyzed using image processing techniques. Two weather stations provide reference values for precipitation and relevant meteorological variables for wind speed and direction, air humidity, temperature and irradiation. The amount and distribution of precipitation measured in scarcely vegetated areas of the catchment widely correspond with values from the reference weather stations. Under dense vegetation, very heterogeneous values were recorded, which can be explained by i) canopy interception, and ii) fetching effects. The results of this study can serve as basis for interception models and may also contribute to complex eco-hydrological models.}, language = {en} } @inproceedings{MaurerCaviedesVoulliemeHinzetal., author = {Maurer, Thomas and Caviedes-Voulli{\`e}me, Daniel and Hinz, Christoph and Gerke, Horst H.}, title = {Flow processes on the catchment scale - modeling of initial structural states and hydrological behavior in an artificial exemplary catchment}, series = {European Geosciences Union General Assembly 2017 Vienna, Austria, 23-28 April 2017}, booktitle = {European Geosciences Union General Assembly 2017 Vienna, Austria, 23-28 April 2017}, publisher = {European Geophysical Society}, address = {Katlenburg-Lindau}, abstract = {Landscapes that are heavily disturbed or newly formed by either natural processes or human activity are in a state of disequilibrium. Their initial development is thus characterized by highly dynamic processes under all climatic conditions. The primary distribution and structure of the solid phase (i.e. mineral particles forming the pore space) is one of the decisive factors for the development of hydrological behavior of the eco-hydrological system and therefore (co-) determining for its - more or less - stable final state. The artificially constructed ‚H{\"u}hnerwasser' catchment (a 6 ha area located in the open-cast lignite mine Welzow-S{\"u}d, southern Brandenburg, Germany) is a landscape laboratory where the initial eco-hydrological development is observed since 2005. The specific formation (or construction) processes generated characteristic sediment structures and distributions, resulting in a spatially heterogeneous initial state of the catchment. We developed a structure generator that simulates the characteristic distribution of the solid phase for such constructed landscapes. The program is able to generate quasi-realistic structures and sediment compositions on multiple spatial levels (1 cm up to ∼ 100 m scale). The generated structures can be i) conditioned to actual measurement values (e.g., soil texture and bulk distribution); ii) stochastically generated, and iii) calculated deterministically according to the geology and technical processes at the excavation site. Results are visualized using the GOCAD software package and the free software Paraview. Based on the 3D-spatial sediment distributions, effective hydraulic van-Genuchten parameters are calculated using pedotransfer functions. The hydraulic behavior of different sediment distribution (i.e. versions or variations of the catchment's porous body) is calculated using a numerical model developed by one of us (Caviedes-Voulli{\`e}me). Observation data are available from catchment monitoring are available for i) determining the boundary conditions (e.g., precipitation), and ii) the calibration / validation of the model (catchment discharge, ground water). The analysis of multiple sediment distribution scenarios should allow to approximately determine the influx of starting conditions on initial development of hydrological behavior. We present first flow modeling results for a reference (conditioned) catchment model and variations thereof. We will also give an outlook on further methodical development of our approach.}, language = {en} } @inproceedings{PohleNiebischZhaetal., author = {Pohle, Ina and Niebisch, Michael and Zha, Tingting and Sch{\"u}mberg, Sabine and M{\"u}ller, Hannes and Maurer, Thomas and Hinz, Christoph}, title = {A stochastical event-based continuous time step rainfall generator based on Poisson rectangular pulse and microcanonical random cascade models}, series = {European Geosciences Union General Assembly 2017 Vienna, Austria, 23-28 April 2017}, booktitle = {European Geosciences Union General Assembly 2017 Vienna, Austria, 23-28 April 2017}, publisher = {European Geophysical Society}, address = {Katlenburg-Lindau}, abstract = {Rainfall variability within a storm is of major importance for fast hydrological processes, e.g. surface runoff, erosion and solute dissipation from surface soils. To investigate and simulate the impacts of within-storm variabilities on these processes, long time series of rainfall with high resolution are required. Yet, observed precipitation records of hourly or higher resolution are in most cases available only for a small number of stations and only for a few years. To obtain long time series of alternating rainfall events and interstorm periods while conserving the statistics of observed rainfall events, the Poisson model can be used. Multiplicative microcanonical random cascades have been widely applied to disaggregate rainfall time series from coarse to fine temporal resolution. We present a new coupling approach of the Poisson rectangular pulse model and the multiplicative microcanonical random cascade model that preserves the characteristics of rainfall events as well as inter-storm periods. In the first step, a Poisson rectangular pulse model is applied to generate discrete rainfall events (duration and mean intensity) and inter-storm periods (duration). The rainfall events are subsequently disaggregated to high-resolution time series (user-specified, e.g. 10 min resolution) by a multiplicative microcanonical random cascade model. One of the challenges of coupling these models is to parameterize the cascade model for the event durations generated by the Poisson model. In fact, the cascade model is best suited to downscale rainfall data with constant time step such as daily precipitation data. Without starting from a fixed time step duration (e.g. daily), the disaggregation of events requires some modifications of the multiplicative microcanonical random cascade model proposed by Olsson (1998): Firstly, the parameterization of the cascade model for events of different durations requires continuous functions for the probabilities of the multiplicative weights, which we implemented through sigmoid functions. Secondly, the branching of the first and last box is constrained to preserve the rainfall event durations generated by the Poisson rectangular pulse model. The event-based continuous time step rainfall generator has been developed and tested using 10 min and hourly rainfall data of four stations in North-Eastern Germany. The model performs well in comparison to observed rainfall in terms of event durations and mean event intensities as well as wet spell and dry spell durations. It is currently being tested using data from other stations across Germany and in different climate zones. Furthermore, the rainfall event generator is being applied in modelling approaches aimed at understanding the impact of rainfall variability on hydrological processes.}, language = {en} } @inproceedings{CaviedesVoulliemeDominFernandezPatoetal., author = {Caviedes-Voulli{\`e}me, Daniel and Domin, Andrea and Fern{\´a}ndez-Pato, Javier and Hinz, Christoph}, title = {A numerical study on the influence of m{\`i}crotopography on ra{\`i}nfall-runoff-infiltration partitioning}, series = {4th International Symposium of Shallow Flows (ISSF 2017), Eindhoven University of Technology, The Netherlands, 26.-28.06.2017}, booktitle = {4th International Symposium of Shallow Flows (ISSF 2017), Eindhoven University of Technology, The Netherlands, 26.-28.06.2017}, abstract = {Microtopographic features, although minute relative to the hillslope scales, are not insignificant in terms of runoff generation, rain-runoff-infiltration partitioning and overall hillslope hydrological signals. As-sessing the effects of such small scale features, arguably requires mathematical models that can cope with microtopraphic complexity to adequately represent surface water dynamics, which in turn deter-mine hydrological signals at the hillslope scale. In this work, rain-runoff simulations are perfomed with a 2D shallow water model on a rectangular domain representing a hillslope with an idealized 2D sinusoidal microtopography. Several combinations of slope, wavelength and amplitudes were used to create over 500 surfaces on which simulations were performed in order to assess their hydrological response in terms of rainfallrunoff-infiltration partitioning. The results were analysed through several dimensionless indices which allow to observe the dependency of characteristic hydrological responses to mi-crotopography properties. They reveal a complex dependency of hydrological signatures to surface microtopography. In particular, the results show that the fraction of rainfall that results in infiltration is increased following a particular non-linear dependency on surface smoothness. Additionally, hydrograph properties and surface flow connectivity also show emerging patterns in response to microtopography.}, language = {en} } @inproceedings{PohleGaedekeKochetal., author = {Pohle, Ina and G{\"a}deke, Anne and Koch, Hagen and Sch{\"u}mberg, Sabine and Hinz, Christoph}, title = {Can water resources management alleviate the uncertainty of projected climate change impacts on river discharge? - A comparative study in two hydrologically similar catchments with different level of management}, series = {International Soil and Water Assessment Tool Conference. SWAT 2017, June 28 - 30, Warsaw, Poland, Book of Abstracts}, booktitle = {International Soil and Water Assessment Tool Conference. SWAT 2017, June 28 - 30, Warsaw, Poland, Book of Abstracts}, pages = {10 -- 11}, abstract = {Climate change impact studies are associated with error propagation and amplification of uncertainties through model chains from global climate models down to impact (e.g. hydrological) models. The effect of water management, which reduces discharge variability, is often not considered in climate change impact studies. Here, we investigated how water resources management influences discharge variability and uncertainty propagation of climate change scenarios by combining the analyses of observed flow records and model-based climate change impact simulations. Two neighbouring catchments, the Schwarze Elster River (Germany) and the Spree River (Germany and Czech Republic) which are similar in climate, topography and land use, but different in terms of water resources management were chosen as study area. The intense water resources management in the Spree River catchment includes a high reservoir capacity, water use in terms of mining discharges and water withdrawals by power plants as well as water transfers. The analysis of historical flow records focusses on variability indices (Parde index, Richards-Baker-Flashiness Index, Interquartile Ratio and Baseflow Index). The climate change impact simulations were carried out using a model cascade of (i) the statistical regional model STAR (100 stochastically generated realizations each for 3 scenarios with different prescribed temperature trend), (ii) the hydrological models SWIM and EGMO, and (iii) the water resources management model WBalMo. The analysis of the observed discharges reveals that the annual discharge variability in the Spree catchment is dominated by mining activities rather than natural rainfall-runoff processes. Due to the high reservoir capacity in the Spree catchment its discharge is characterised by less seasonality and short-term variability compared to the Schwarze Elster. Simulations with climate change scenarios assuming increasing temperature and decreasing precipitation result in pronounced reductions of discharge in both catchments. The differences in potential natural discharges between the Schwarze Elster and the Spree catchments as projected by the hydrological models SWIM and EGMO are marginal. The uncertainties related to the climate projection are propagated through the hydrological models. In the Schwarze Elster catchment, the managed discharges simulated by WBalMo are comparable to the potential natural discharges. In the Spree River however, the short-term variability is moderated by water resources management and managed discharge under climate change is less affected by amplification of uncertainties through model chains. The results of the study, which combines the analyses of observed flow records and model-based climate change impact simulations, imply that generally, effective water resources management reducing discharge variability hence also reduces uncertainty related to climate change impacts on river discharge. Catchments with a high storage ratio are thus less vulnerable to changing climate conditions. This underlines the role of water resources management in coping with climate change impacts. Yet, due to decreasing reservoir volumes in drought periods, reservoir management alone cannot compensate strong changes in climate conditions over long time periods.}, language = {en} } @inproceedings{BrueckSchulteOverbergPohleetal., author = {Br{\"u}ck, Yasemine and Schulte-Overberg, Philipp and Pohle, Ina and Hinz, Christoph}, title = {{\"O}kohydrologische Systeme im Wandel: NDVI von Tagebaufolgelandschaften}, series = {M³ - Messen, Modellieren, Managen in Hydrologie und Wasserressourcenbewirtschaftung. Beitr{\"a}ge zum Tag der Hydrologie am 22./23. M{\"a}rz 2018 an der Technischen Universit{\"a}t Dresden}, booktitle = {M³ - Messen, Modellieren, Managen in Hydrologie und Wasserressourcenbewirtschaftung. Beitr{\"a}ge zum Tag der Hydrologie am 22./23. M{\"a}rz 2018 an der Technischen Universit{\"a}t Dresden}, editor = {Sch{\"u}tze, Niels and M{\"u}ller, Uwe and Schwarze, Robert and W{\"o}hling, Thomas and Grundmann, Jens}, publisher = {Technische Universit{\"a}t}, address = {Dresden}, pages = {S. 113}, abstract = {Tagebau(folge)landschaften bieten gute M{\"o}glichkeiten den Wandel {\"o}kohydrologische Systeme aufgrund ver{\"a}nderter Umweltbedingungen zu untersuchen: Im Zuge des Tagebaubetriebs wird die Vegetation vollst{\"a}ndig entfernt, nach dem Tagebau w{\"a}chst die Vegetation entweder durch aktive Rekultivierung oder nat{\"u}rliche Sukzession wieder auf. Von Interesse ist, ob und wie bzw. wie schnell sich die Tagebaufl{\"a}chen von der St{\"o}rung erholen und {\"a}hnliche Bedingungen wie vor dem Tagebau bzw. auf ungest{\"o}rten Fl{\"a}chen herrschen. Klimatische, geomorphologische und {\"o}kologische Gegebenheiten sowie die Rekultivierungsstrategie spielen eine große Rolle in der Phase der Rehabilitation und bestimmen die Rate der Wiederbesiedlung mit Pflanzen bzw. deren Wachstum. Der NDVI (normalisierter differenzierter Vegetationsindex) bietet die M{\"o}glichkeit generelle Muster der Vegetation quantitativ zu detektieren, um die Regenerationsrate der Vegetation f{\"u}r verschiedene Klima- und {\"O}koregionen abzusch{\"a}tzen. Wir analysierten den MODIS Terra NDVI (achtt{\"a}gliche Werte) f{\"u}r Tagebaulandschaften verschiedener Klimate ({\"a}quatoriale, trockene, warm gem{\"a}ßigte und Schnee-Klimate nach K{\"o}ppen-Geiger) im Zeitraum 2001 bis 2015. Es wurden Kohletagebaue betrachtet, da diese gut definierte Chronosequenzen der St{\"o}rung erzeugen. Bei der Analyse der NDVI-Zeitreihen sollten Charakteristiken der Rehabilitationsphase erfasst werden. Um die r{\"a}umliche Heterogenit{\"a}t der Zellen (ca. 250 x 250 m²) der Tagebaulandschaft abzubilden, wurde je Tagebau eine hierarchische Clusteranalyse durchgef{\"u}hrt. Die einzelnen Zeitreihen der Cluster wurden mit einer Methode zur Detektion von Bruchpunkten und zur Zeitreihenzerlegung auf Konsistenz bez{\"u}glich Eigenschaften der Zeitreihen (Beginn des Tagebaus, Ende des Tagebaus/Beginn der Rehabilitation, Rate der Rehabilitation) untersucht. Die Clusteranalyse f{\"u}hrt zu einer Einordnung der Zellen in vom Tagebau nicht direkt beeinflusste Fl{\"a}chen, aktiven Tagebau und in der Rehabilitation befindliche Fl{\"a}che verschiedenen Alters bzw. rehabilitierte Fl{\"a}chen. Das Zeitfenster der Entfernung der Vegetation kann im NDVI-Signal identifiziert werden, es zeigt sich meist in einer abrupten {\"A}nderung des NDVI. Die Rehabilitationsphase hingegen verl{\"a}uft graduell und kann mehrere Jahre bis Jahrzehnte andauern. Die Zeitreihenzerlegung zeigt auf, dass in der Rehabilitationsphase der Trend dominiert, w{\"a}hrend mit Voranschreiten der Rehabilitation die Saisonalit{\"a}t im NDVI-Signal vorherrschend wird. Durch die ermittelte Rate der Rehabilitation k{\"o}nnen die Fl{\"a}chen innerhalb eines Tagebaus miteinander verglichen werden. Die mittlere Rehabilitationsrate der Tagebaue kann in Zusammenhang mit den vorherrschenden hydroklimatischen Bedingungen der Klimazonen und mit Rekultivierungsstrategien gebracht werden. Zudem ist auch eine Betrachtung hydrometeorologischer Gr{\"o}ßen zur Erkennung von kurzzeitigen Ver{\"a}nderungen des Pflanzenwachstums im NDVI-Signal m{\"o}glich.}, language = {de} } @inproceedings{CaviedesVoulliemeAndezhathMohananBruecketal., author = {Caviedes-Voullieme, Daniel and Andezhath Mohanan, Anju and Br{\"u}ck, Yasemine and Zaplata, Markus K. and Hinz, Christoph}, title = {Effect of surface water redistribution on vegetation encroachment in the constructed H{\"u}hnerwasser catchment}, series = {M³ - Messen, Modellieren, Managen in Hydrologie und Wasserressourcenbewirtschaftung. Beitr{\"a}ge zum Tag der Hydrologie am 22./23. M{\"a}rz 2018 an der Technischen Universit{\"a}t Dresden}, booktitle = {M³ - Messen, Modellieren, Managen in Hydrologie und Wasserressourcenbewirtschaftung. Beitr{\"a}ge zum Tag der Hydrologie am 22./23. M{\"a}rz 2018 an der Technischen Universit{\"a}t Dresden}, editor = {Sch{\"u}tze, Niels and M{\"u}ller, Uwe and Schwarze, Robert and W{\"o}hling, Thomas and Grundmann, Jens}, publisher = {Technische Universit{\"a}t}, address = {Dresden}, pages = {S. 91}, abstract = {The artificial H{\"u}hnerwasser catchment has experienced a significant and monitored evolution since 2005, changing from a post-mining landscape to an almost fully vegetated ecosystem. The early stages showed a fast rate of ecohydrological evolution with changing dominating processes and feedbacks. The evolution of rill vegetation encroachment is one of such complex co-evolving processes. We hypothesise that rill vegetation encroachment is driven by the evolution of the hydrologic/hydraulic regime of the rill network, which in turn affects the regime, potentially creating a stabilising positive feedback. We further hypothesise that rill vegetation occurs later than hillslope vegetation, and follows a particular establishment and encroachment timeline in response to the changing hydrological/hydraulic regimes. That is, the early runoff-dominated regime results in higher flows, velocities, transport and erosion capacity, thus favouring seed flushing and seedling uprooting. On the other hand, as the system transitions from a runoffdominated into an infiltration- and ET-dominated system, flow, velocity, transport and erosion capacity in the rill network are reduced, making seed establishment in the rills more likely. We explore these hypothesis with two complementary approaches: an analysis of the spatiotemporal distribution of vegetation and a process-based numerical modelling study. Firstly, we assess aerial photography of rill vegetation encroachment between 2007 and 2012 in terms of several vegetation types to derive temporal indicators of encroachment. The analysis reveals that in the initial stages, a rill network developed in the hillslope. Shortly after vegetation first established on hillslopes, the rill network became progressively vegetated. Different pioneering species established heterogeneously, at different times and encroached into the rills at different rates. However, despite the volume of data, it is difficult to assess which are the governing and limiting processes which respectively drive and constrain how and at which rate vegetation encroaches into the rills. In consequence, a pilot modelling study to identify the relative relevance of rill network geometry, bare soil infiltration, hillslope vegetation heterogeneity and intra-storm variability on the hydraulic response of the rill network and its possible impact on encroachment. The overall results suggest that vegetation encroachment may be controlled by the rill network hydraulic regime, but such regime is the result of a complex superposition of responses of all the aforementioned factors, of which rill geometry appears to be a dominant one. Furthermore, the simulations showed that vegetation spatial heterogeneity has an impact on the hydraulic regime coupled to the presence of temporal rainfall variability. Altogether, these results show that the governing coevolving ecohydrological processes are interacting and are strongly affected by spatial and temporal heterogeneities.}, language = {en} } @inproceedings{PohleGaedekeKochetal., author = {Pohle, Ina and G{\"a}deke, Anne and Koch, Hagen and Sch{\"u}mberg, Sabine and Hinz, Christoph}, title = {Kann Wasserressourcenbewirtschaftung die Unsicherheiten projizierter Klimafolgen auf den Abfluss vermindern? - Ein Vergleich in zwei hydrologisch {\"a}hnlichen Einzugsgebieten mit unterschiedlichem Ausmaß des Bewirtschaftungseinflusses}, series = {M³ - Messen, Modellieren, Managen in Hydrologie und Wasserressourcenbewirtschaftung. Beitr{\"a}ge zum Tag der Hydrologie am 22./23. M{\"a}rz 2018 an der Technischen Universit{\"a}t Dresden}, booktitle = {M³ - Messen, Modellieren, Managen in Hydrologie und Wasserressourcenbewirtschaftung. Beitr{\"a}ge zum Tag der Hydrologie am 22./23. M{\"a}rz 2018 an der Technischen Universit{\"a}t Dresden}, editor = {Sch{\"u}tze, Niels and M{\"u}ller, Uwe and Schwarze, Robert and W{\"o}hling, Thomas and Grundmann, Jens}, publisher = {Technische Universit{\"a}t}, address = {Dresden}, pages = {S. 30}, abstract = {Studien zum Einfluss des zuk{\"u}nftigen Klimawandels auf das Abflussgeschehen fokussieren oft auf die Fortpflanzung von Unsicherheiten in Modellkaskaden, ber{\"u}cksichtigen meist jedoch die Wasserressourcenbewirtschaftung nur ungen{\"u}gend. Wir untersuchten den Einfluss der Wasserressourcenbewirtschaftung auf die Abflussvariabilit{\"a}t und die Fortpflanzung von Unsicherheiten von Klimaprojektionen auf Abflusssimulationen in den Einzugsgebieten von Spree (bis Pegel Große Tr{\"a}nke: 6200 km²) und Schwarzer Elster (5700 km²). Die Einzugsgebiete {\"a}hneln sich hinsichtlich Klima, Topographie, Boden und Landnutzung, jedoch ist das Spreeeinzugsgebiet st{\"a}rker durch den Braunkohletagebau und die damit verbundenen Bewirtschaftung gepr{\"a}gt und durch einen h{\"o}heren Speicherausbaugrad gekennzeichnet. Um zwischen Bewirtschaftungseinfl{\"u}ssen und meteorologischen Einfl{\"u}ssen zu separieren, wurden f{\"u}r den Zeitraum 1961-2005 beobachtete Abfl{\"u}sse mit durch das Modell SWIM rekonstruierten nat{\"u}rlichen (d.h. ohne Bewirtschaftungseinfluss) Abfl{\"u}ssen der Vergangenheit verglichen. M{\"o}gliche Einfl{\"u}sse des Klimawandels wurden f{\"u}r den Zeitraum 2018-2052 auf Grundlage von 3 Szenarien des statistischen Regionalmodells STAR (je 100 Realisierungen) mit SWIM (nat{\"u}rliche Abfl{\"u}sse) und dem Langfristbewirtschaftungsmodell WBalMo (bewirtschaftete Abfl{\"u}sse) modelliert. Die Analyse erfolgte mit Fokus auf Saisonalit{\"a}t, Oszillation, Verteilung und r{\"a}umliche Variabilit{\"a}t der Abfl{\"u}sse. Der Vergleich zwischen beobachteten und nat{\"u}rlichen Abfl{\"u}ssen der vergangenen Jahrzehnte zeigt, dass die zwischenj{\"a}hrliche Abflussvariabilit{\"a}t im Spreeeinzugsgebiet st{\"a}rker durch Grubenwassereinleitungen als durch nat{\"u}rliche hydrologische Prozesse bestimmt wurde. Zus{\"a}tzlich f{\"u}hrt der h{\"o}here Speicherausbaugrad dazu, dass die kurzzeitliche und saisonale Variabilit{\"a}t im Spreeeinzugsgebiet geringer als im Einzugsgebiet der Schwarzen Elster ist. Simulationen mit Klimaszenarien, welche steigende Jahresmitteltemperaturen und einen R{\"u}ckgang der Niederschlagsjahressummen enthalten, f{\"u}hren zu deutlichen Abflussr{\"u}ckg{\"a}ngen. Die Unterschiede der nat{\"u}rlichen Abfl{\"u}sse beider Einzugsgebiete sind gering, die Unsicherheiten der Klimaprojektionen werden durch die hydrologische Modellierung verst{\"a}rkt. Die nat{\"u}rlichen und bewirtschafteten Abfl{\"u}sse der Schwarzen Elster unter Klimawandel unterscheiden sich kaum. Im Spreeeinzugsgebiet zeigt sich eine deutliche Verringerung der Variabilit{\"a}t und Unsicherheiten unter Klimawandel von den nat{\"u}rlichen zu den bewirtschafteten Abfl{\"u}ssen. Die Analysen zeigen, dass effektive Wasserressourcenbewirtschaftung die Abflussvariabilit{\"a}t verringern kann und damit auch dazu beitragen kann, die sich aus Klimawandelprojektionen ergebenden Unsicherheiten zu vermindern. Einzugsgebiete mit einem hohen Ausbaugrad weisen weniger Vulnerabilit{\"a}t bez{\"u}glich klimatischer {\"A}nderungen auf. Dies unterstreicht die Bedeutung von Wasserresourcenbewirt-schaftungf{\"u}r die Anpassung an den Klimawandel.}, language = {de} } @inproceedings{CaviedesVoulliemeHinz, author = {Caviedes-Voulli{\`e}me, Daniel and Hinz, Christoph}, title = {The role of topography and intra-annual rainfall variability in semi-arid vegetation self-organisation: a multi-scale modelling study}, series = {European Geosciences Union, General Assembly 2018, Vienna, Austria}, booktitle = {European Geosciences Union, General Assembly 2018, Vienna, Austria}, publisher = {European Geophysical Society}, address = {Katlenburg-Lindau}, abstract = {Coevolution of hydrological and vegetation dynamics in semi-arid regions has been widely observed to result in vegetation self-organisation (VSO). Many hypothesis of VSO's underlying ecohydrological processes and feedbacks have been studied relying on mathematical models, which have been key to evaluate the sensitivity of ecohydrological systems to environmental factors and drivers. Although this ecohydrological coevolution is essentially multiscale, researchers have continued to be constrained by the simplicity of the models which are unable to cope with the multiscale, process-based complexity of fast-moving surface water over complex topographies driven by varying rainfall, during decade-to-century long VSO processes. This limitation has not allowed deep exploration of the role and sensitivity of key environmental factors such as topography and rainfall variability, and the lack of proper hydrodynamics still constrains adequate sediment transport modelling and its feedback effects on VSO. We hypothesize that the intra-storm water redistribution by surface runoff at the hillslope scale is strongly controlled by both topography and storm intensity and may control VSO. This requires for these environmental factors to be accurately represented in models and their their hydraulic and hydrological effects properly reflected. This work provides the first systematic study of the effects of topography and intra-annual rainfall distributions on vegetation band formation at the hillslope scale. Simulations were performed with a physically-based numerical model solving the Zero-Inertia approximation to the shallow water equations for surface flow coupled to the HilleRisLambers-Rietkerk vegetation model, allowing to explicitly represent arbitrary topography. An idealized study of ecohydrological evolution over 30 years was performed, solving with a temporal resolution in the seconds scale. Plane, convex and convex hillslope topologies with different slopes were used, while forcing the model with different annual rainfalls along a semi-arid rainfall gradient, with discrete events of different frequencies. We describe results in terms of evolution of total biomass, hydrological water balance, and of the spatial properties of banded vegetation. Results show that both topography and intra-annual rainfall distribution can play a shaping and governing role in VSO by controlling surface water redistribution and the hydrologic water balance. Increasing slopes favours runoff over infiltration, reducing the available water for vegetation and resulting in different evolutions of vegetation band geometry and band migration. Hillslope topology plays a strong role in the internal water redistribution of the system. Plane and convex surfaces behave similarly, but concave surfaces exhibit a different ecohydrological behaviour, despite the very small topological differences. Different intra-annual rainfall distributions result in different rainfall intensities for the same total annual rainfall which strongly affect the band formation and evolution process: higher intensities lead to less available water, to which vegetation adapts by spatially clustering in bands with different geometrical properties. The study also shows that it is computationally feasible (a few hours runtime) to perform decade-to-century long simulations of these systems with physically-based numerical models paving the way to simulate natural systems with arbitrary topography and high-resolution rainfall data, and is a first step in introducing physically-based sediment transport processes and feedbacks in these studies.}, language = {en} } @inproceedings{BrueckAndezhathMohananCaviedesVoulliemeetal., author = {Br{\"u}ck, Yasemine and Andezhath Mohanan, Anju and Caviedes-Voulli{\`e}me, Daniel and Hinz, Christoph and Zaplata, Markus K.}, title = {Spatio-temporal development of rill vegetation in the H{\"u}hnerwasser Catchment}, series = {European Geosciences Union, General Assembly 2018, Vienna, Austria}, booktitle = {European Geosciences Union, General Assembly 2018, Vienna, Austria}, publisher = {European Geophysical Society}, address = {Katlenburg-Lindau}, abstract = {The artificial catchment "H{\"u}hnerwasser" was built in a post-mining landscape, as a field experiment to observe and monitor early-development ecosystems at hillslope scale. Early on, rain-induced rill and channels formation was observed, followed by vegetation growth in between rills, and later on inside the rills. In this work, we aim to describe the temporal evolution of the spatial distribution of rill vegetation. In general terms, we hypothesize four different encroachment patterns might occur: (1) The vegetation spreads from the top of the rills downstream. The underlying hypothesis would be a higher establishment probability due to a lower velocity of surface runoff and therefore less transport probability compared to downstream rill segments. (2) The vegetation starts growing downstream and moves upwards. In this case we can hypothesize that the spatial distribution of the vegetation is dominated by water availability, which is higher or more stable downstream. (3) The vegetation encroaches from the sides into the rills, meaning that inter-rill vegetation governs vegetation encroachment inside the rills. (4) If no patterns are detected it might mean that the encroachment process depends strongly on very local conditions, or perhaps that the underlying assumption of an initially homogeneous seed distribution is false. To investigate the rills formation and rill vegetation encroachment processes, rills and vegetation patches inside these rills were identified and digitized from aerial photographs of the catchment from 2007 to 2012. Different vegetation types were identified based on the colour and texture of the patches. The geometrical properties of the rill segments and vegetation patches were used to define how the different vegetation types have distributed in space and how this distribution has changed over time. Rill mapping reveals a large increase of rill area from 2007 to 2008 and only a small rise from 2008 to 2009. Starting in 2010 dense vegetation prevents a precise mapping of the rills in the aerial photographs, so we assume that there is no change in rill area from 2009 to 2012. In 2007 vegetation covered only 1.4\% of the rill area. There is only a small increase of this area in 2008 compared to the later years. In 2012 more than 50\% of the rill area is covered by plants. Ten different vegetation types have been identified in the aerial photographs, starting with two types in 2007. By 2012 nine types are spotted in the rills of the catchment. Some of these vegetation types show an encroachment from up- to downstream (e.g. Tussilago farfara), some from down- to upstream like Phragmites australis, whose creeping rhizomes can also promote such spreading. Others reveal no patterns. To better assess and identify the underlying processes leading to these encroachment processes shown by the different vegetation types further data analysis -e.g. comparison with ground based vegetation mapping- and process-based hydrological modelling is necessary to fully explain these observations and assessing additional competition effects, which may be at play.}, language = {en} } @inproceedings{CaviedesVoulliemeAndezhathMohananBruecketal., author = {Caviedes-Voulli{\`e}me, Daniel and Andezhath Mohanan, Anju and Br{\"u}ck, Yasemine and Hinz, Christoph}, title = {Rill hydrodynamics and its impact on rill vegetation encroachment: a modelling study of the constructed H{\"u}hnerwasser catchment}, series = {European Geosciences Union, General Assembly 2018, Vienna, Austria}, booktitle = {European Geosciences Union, General Assembly 2018, Vienna, Austria}, publisher = {European Geophysical Society}, address = {Katlenburg-Lindau}, abstract = {The H{\"u}hnerwasser catchment is a monitored, early-development constructed catchment within the Lower Lausatia post-mining landscape in Germany. Observations have shown that a sequence of landscape-forming processes occurred, including the initial vegetation establishment stages, which are the main interest of this study. In the initial stages of geomorphic development a surface drainage network of rills was formed as vegetation started to appear on the hillslopes and subsequently inside the rill network. Observations and analysis of the rill vegetation establishment suggest that different vegetation types encroach into the rill network at different times, rates and form different directions. We hypothesize that these encroachment processes may respond to the runoff properties of the catchment at such time: velocity distribution in the rills might play a significant role in flushing seeds in high-velocity reaches of the rill network, thus favouring the appearance of vegetation in low-velocity regions. Consequently, the goal of this study is to assess the magnitudes and spatiotemporal behaviour of velocity in the rill network, to assess its possible impact on seed flushing and rill vegetation encroachment. One rill subcatchment of H{\"u}hnerwasser was selected to perform an explorative study of rill hydrodynamics and their impact on vegetation establishment. Two vegetation states were simulated: bare hillslopes and vegetated hillslopes. The vegetated cover polygons were obtained from digitized aerial photography, and stochastically dissagregated 10-minute resolution precipitation data were used, selecting events with early, middle and late peak storm intensities. A 2D explicit finite volume scheme solving the Zero-Inertia approximation to the shallow water equations was used to simulate surface flow in the subcatchment. The preliminary modelling results suggest that that there is no clear overall velocity gradient in the downstream direction along the rills. In fact, velocity in the rills may increase or decrease along the rill following local topography and rill geometry. Consequently, no global trend for the probability of seeds being transported can be established. The results also shows that varying rainfall intensity and rainfall intrastorm distribution -in the absence of hillslope vegetation- does not affect the rill locations of maximum velocities, but mostly affect the magnitude of velocity. In the presence of hillslope vegetation -and thus heterogeneous infiltration conditions in the hillslopes- the spatial distribution of velocity is strongly affected, and can be in fact governed not by topography or rill geometry, but by the spatial heterogeneity of infiltration capacity. Furthermore, the time at which maximum discharge and velocities occur may not match that of maximum intensity. That is, emerging temporal dynamics arise due to the introduction of spatial heterogeneity, which also manifests in the fact that outflow from the subcatchment exhibits a intensity-thresholded behaviour.}, language = {en} } @inproceedings{CaviedesVoulliemeHinz, author = {Caviedes-Voulli{\`e}me, Daniel and Hinz, Christoph}, title = {Convergent biomass, divergent patterns: Can initial conditions govern vegetation self-organisation?}, series = {European Geosciences Union, General Assembly 2018, Vienna, Austria}, booktitle = {European Geosciences Union, General Assembly 2018, Vienna, Austria}, publisher = {European Geophysical Society}, address = {Katlenburg-Lindau}, abstract = {Vegetation self-organisation in water-limited ecosystems in semi-arid climates has been extensively studied by means of numerical simulation using a set of different reaction-diffusion-equations. Most of such models and studies have been concerned with the long-term steady ecohydrological states on domains with periodic boundaries and forced by steady rainfall, whilst little interest has been given to the transient states which lead to them as well as the spatiotemporal multiscale nature of the feedback processes. It is generally accepted that alternative random initial biomass distributions do not significantly affect the resulting steady state vegetation patterns. However, the role of the initial hydrological conditions -initial surface and subsurface water- has not been explored, mainly due to the interest in the long-term steady state. Nonetheless, vegetation patterns are directly linked to the water distribution occurring at much shorter time scales than vegetation growth, and because they have been shown to be sensitive to annual rainfall, it is reasonable that the initially available water will also play a role. We therefore hypothesize that the initially available water will play a role in the transient process leading to a steady ecohydrological state, and that the steady vegetation patterns will differ in response to the water availability in time during the entire process. In this contribution we explore the role of initial hydrological conditions on both the transient and longterm steady ecohydrological state. A simulation study was performed using the HilleRisLambers-Rietkerk ecohydrological model on a flatland varying the initial available water whilst also spanning the rainfall gradient (90 - 360 mm/year) . The results were assessed in terms of the evolution and steady state of total biomass yield and hydrological water balance, as well as a quantitative assessment of both transient and steady vegetation patterns. The results show that the initially available water does play a role, not only in the early transient state, but in the long-term steady state, and indeed in the geometry of the converged vegetation pattern. Furthermore, although the steady state biomass yield may be the same for varying initial conditions, the final patterns still differ, e.g., a reduction to one-fourth initial water availability results in more but smaller vegetation patches, while a reduction to one-eigth initial water results in less, but larger patches, and a reduction to one-sixteenth results in a completely new pattern, although total biomass is the same for all. This suggests that long-term average rainfall may govern the total biomass but the initial conditions may play a relevant shaping role in the long term spatial distributions of steady ecohydrological states of water-limited ecohydrosystems. This is relevant, among other reasons, because the resilience of the system is associated to the vegetation patterns. It also suggests that neither the temporal distribution of rainfall nor the system's evolution cannot be neglected to understand the environmental factors which lead to a steady ecohydrological state, since multiple paths may be possible. This warrants further developments from the ecohydrological modelling community and further study of transient states through process-based models.}, language = {en} } @misc{CaviedesVoulliemeFernandezPatoHinz, author = {Caviedes-Voulli{\`e}me, Daniel and Fern{\´a}ndez-Pato, Javier and Hinz, Christoph}, title = {Cellular Automata and Finite Volume solvers converge for 2D shallow flow modelling for hydrological modelling}, series = {Journal of Hydrology}, volume = {563}, journal = {Journal of Hydrology}, issn = {0022-1694}, doi = {10.1016/j.jhydrol.2018.06.021}, pages = {411 -- 417}, abstract = {Surface flows of hydrological interest, including overland flow, runoff, river and channel flow and flooding have received significant attention from modellers in the past 30 years. A growing effort to address these complex environmental problems is in place in the scientific community. Researchers have stud-ied and favoured a plethora of techniques to approach this issue, ranging from very simple empirically-based mathematical models, to physically-based, deductive and very formal numerical integration of systems of partial-differential equations. In this work, we review two families of methods: cell-based simulators - later called Cellular Automata - and Finite Volume solvers for the Zero-Inertia equation, which we show to converge into a single methodology given appropriate choices. Furthermore, this convergence, mathematically shown in this work, can also be identified by critically reviewing the exist-ing literature, which leads to the conclusion that two methods originating from different reasoning and fundamental philosophy, fundamentally converge into the same method. Moreover, acknowledging such convergence allows for some generalisation of properties of numerical schemes such as error behaviour and stability, which, importantly, is the same for the converging methodology, a fact with practical implications. Both the review of existing literature and reasoning in this work attempts to aid in the effort of synchronising and cross-fertilizing efforts to improve the understanding and the outlook of Zero-Inertia solvers for surface flows, as well as to help in clarifying the possible confusion and parallel develop-ments that may arise from the use of different terminology originating from historical reasons. Moreover, synchronising and unifying this knowledge-base can help clarify model capabilities, applicability and modelling issues for hydrological modellers, specially for those not deeply familiar with the mathematical and numerical details.}, language = {en} } @inproceedings{CaviedesVoulliemeFernandezPatoHinz, author = {Caviedes-Voulli{\`e}me, Daniel and Fern{\´a}ndez-Pato, Javier and Hinz, Christoph}, title = {Zero-Inertia vs full shallow water equations: a comparison for rainfall-runoff modelling}, series = {Computational Methods in Water Resources XXII (CMWR 2018), Bridging gaps between data, models, and predictions}, booktitle = {Computational Methods in Water Resources XXII (CMWR 2018), Bridging gaps between data, models, and predictions}, pages = {2}, language = {en} } @inproceedings{CaviedesVoulliemeHinz, author = {Caviedes-Voulli{\`e}me, Daniel and Hinz, Christoph}, title = {An ecohydrological model to explore topographic and rainfall variability effects on vegetation self-organisation}, series = {Computational Methods in Water Resources XXII (CMWR 2018), Bridging gaps between data, models, and predictions}, booktitle = {Computational Methods in Water Resources XXII (CMWR 2018), Bridging gaps between data, models, and predictions}, pages = {2}, language = {en} } @inproceedings{VarraniCaviedesVoulliemeHinz, author = {Varrani, Arianna and Caviedes-Voulli{\`e}me, Daniel and Hinz, Christoph}, title = {Dynamic mapping of surface topografy at rainfall events}, series = {Proceedings of the 5th IAHR Europe Congress — New Challenges in Hydraulic Research and Engineering}, booktitle = {Proceedings of the 5th IAHR Europe Congress — New Challenges in Hydraulic Research and Engineering}, editor = {Armanini, Aronne and Nucci, Elena}, publisher = {IAHR Secretariat, Department of Civil, Environmental and Mechanical Engineering}, address = {Madrid, Spain}, isbn = {978-981-11-2731-1}, pages = {139 -- 140}, abstract = {Landscape evolution forced by rainfall is simulated at the laboratory scale and dynamically tracked using six virtual sensors Kinect™ to ensure detailed meas-urements with relatively low-cost devices.}, language = {en} } @misc{AlmawazrehCaviedesVoulliemeHinz, author = {Almawazreh, Albara and Caviedes-Voulli{\`e}me, Daniel and Hinz, Christoph}, title = {Solute dissipation regimes and rates controlled by soil evaporation and rainfall variability in heterogeneous soils}, series = {European Geosciences Union, General Assembly 2019, Vienna, Austria, 7-12 April 2019}, journal = {European Geosciences Union, General Assembly 2019, Vienna, Austria, 7-12 April 2019}, address = {Katlenburg-Lindau}, abstract = {Reactive solute leaching from the top soil has received wide attention as it relates to major environmental challenges like groundwater and river water pollution by leached reactive solutes such as agricultural pesticides or biochemical pollutants. Adequate understanding of how fast, when and how such solutes and possible contaminants are leached from the top soil is necessary to enhance agricultural practice, pollution risk assessment and overall water quality management. Many empirical studies have been carried on the subject, with varied their approaches and complexity, and have been carried out under different site and atmospheric conditions. Some ofsuch studies argue that properties of soils and solutes are dominant for the leaching process, while others emphasizeatmospheric drivers as a main trigger for preferential flow. Long residence times have also been observed, with solutes lingering in the soils long after initially introduced and after experiencing rainfall events. Modelling and analytical studies have been put forward to better explain these behaviours, but often neglecting some of of the sources of complexity (such as preferential flow and soil heterogeneity) or with simplified modelling strategies. In this work, we study reactive solute dissipation processes in a soil column with a contaminated top soil layer in response to rainfall events. To cope with a heterogeneous soil structure, within an intermediate-complexity and physically-based framework, we solve Richards equation together with a mobile-immobile soil model together with a non-equilibrium advection-diffusion reaction model in Hydrus1D. We perform an extensive analysis of the sensitivity of solute dissipation rates from the top soil in response to all permutations of a parameter space comprised of soil properties (immobile fraction, mobile-immobile mass transfer coefficient), solute properties (decay coefficient, adsorption coefficient), rainfall parameters (total precipitation, duration, frequency) and the presence or absence of evaporation. Results are assessed in terms of the resulting solute dissipation curves and are fitted to exponential decay curves for comparison purposes. The results show that different solute dissipation regimes exist in response to the dominant physical process under a particular set of conditions. We identify three dissipation regimes which exhibit characteristic time scales and dissipation curve shapes: an advection dominated regime occurring under particular rainfall conditions, an evaporation dominated regime occurring under low rainfall volume and intensity and a decay-dominated regime exists, in which the bio- or chemical- decay rate of the substance is large and therefore dominant. Our results also provide further evidence and rationale for long residence times (which have been previously noted in the literature) in the top soil under preferential flow conditions, as the complex interactions between different processes may favour at mobilisation or immobilisation of the solute, which can be related to the characteristic shapes of the dissipation curves and in turn the regimes. The results allow a better understanding of the controlling processes and the related parameters interactions that dominate each regime. The thorough sensitivity analysis shows that, within those regimes, certain properties have higher weight and respectively more attention should be given when investigating them in comprehensive leaching risk assessment.}, language = {en} } @misc{BrueckRojasCaviedesVoulliemeetal., author = {Br{\"u}ck, Yasemine and Rojas, Pedro and Caviedes-Voulli{\`e}me, Daniel and Hinz, Christoph}, title = {Processing of aerial images to detect vegetation cover and evaluate transient vegetation patch characteristics of H{\"u}hnerwasser catchment}, series = {European Geosciences Union, General Assembly 2019, Vienna, Austria, 7-12 April 2019}, journal = {European Geosciences Union, General Assembly 2019, Vienna, Austria, 7-12 April 2019}, address = {Katlenburg-Lindau}, abstract = {The artificial catchment "H{\"u}hnerwasser" was built in a post-mining landscape, as a field experiment to observe and monitor early-development ecosystems at first catchment scale. As vegetation is a key driver of hydrological catchment behavior, spatial distribution and temporal dynamics of vegetation affects water redistribution from plot to catchment scale. In the context of early ecosystem development, quantifying changes in vegetation structures is an obvious indicator for state transitions. The first years of ecosystem development at the H{\"u}hnerwasser catchment showed rapidly increasing complexity of emerging structures associated with rising vegetation cover and increasing number of plant species. This work will focus on characterizing vegetation cover using aerial images aiming to describe spatial structures and how those evolve in time. The early stages are especially of interest. The structure is therefore characterized by the area of the catchment covered by vegetation, the number of vegetation patches, the mean and maximum patch size and a form factor (area of patch divided by its perimeter). Aerial images with a resolution at cm scale were taken once per year from 2007 to 2018. Binary maps are generated by setting thresholds for red, green and blue channels to differentiate between vegetation cover and bare soil. To evaluate the consistency of the binary images of each channel these images were stacked and compared. The performance of the method was tested by using a set of combinations of thresholds and a comparison with manual mapping of vegetation cover at an image subset was made. The blue channel seems to be very sensitive to detect vegetation and a better differentiation of vegetation and dark/wet soil can be achieved by setting the thresholds of the channels in a specific order. The structures derived by the classification into vegetated and bare soil are more important in the early years of ecosystem development. In those years (2007 to 2011) the most changes took place. As time advances vegetation became less patchy and other characteristics need to be implemented to describe the vegetation cover, taking into account different plant functional types.}, language = {en} } @misc{CaviedesVoulliemeHinz, author = {Caviedes-Voulli{\`e}me, Daniel and Hinz, Christoph}, title = {Transient trajectories in vegetation patterns spawning from non-equilibrium initial conditions and singular perturbations}, series = {European Geosciences Union, General Assembly 2019, Vienna, Austria, 7-12 April 2019}, journal = {European Geosciences Union, General Assembly 2019, Vienna, Austria, 7-12 April 2019}, address = {Katlenburg-Lindau}, abstract = {Vegetation self-organisation in water-limited ecosystems in semi-arid climates has been extensively studied by means of numerical simulation using a set of different reaction-diffusion-equations. Most of such models and studies have been concerned with the long-term steady ecohydrological steady states on domains with periodic boundary conditions and forced by steady rainfall. A vast majority of the modelling literature on vegetation self-organisation exists around near-equilibrium conditions. One of the clearest examples of this is that most of the published numerical results have been obtained by evolving near-equilibrium initial conditions to asymptotic steady states, since researchers have been historically interested in the resilience and stability of the systems to perturbation around converged, steady (equilibrium) states and little interest has been given to the transient states which lead to the equilibrium states. Nonetheless, ecohydrological theory recognises that dryland ecosystems can often be far-from-equilibrium systems, in quasi-permanent transient condition, exhibiting non-linear responses to boundary conditions and forcings. This prompts the question of how different the behaviour of the system can be when far-from equilibrium. In this contribution we explore the role of far-from equilibrium initial hydrological conditions on both the transient and long-term asymptotically steady ecohydrological states. A simulation study was performed using the HilleRisLambers-Rietkerk ecohydrological model on a flatland varying the initial available water both near and far from equilibrium whilst also spanning the rainfall gradient (90 - 360 mm/year), performing simulations up to 200 years long. The results were assessed in terms of the evolution of total biomass yield and hydrological water balance, as well as a quantitative assessment of vegetation patterns. The results show that equilibrium conditions always yield smooth system trajectories, with little over- or undershooting, converging to the well-established patterns in the literature. However, as initial conditions move further away from equilibrium, the patterns start to differ, both in their temporal trajectory as in their long-term stable states. Conditions closer to equilibrium generate patterns with quantitative differences when compared to equilibrium conditions (e.g., larger spots). Conditions far from equilibrium can result in an entirely different hybrid patterns, consisting of a mix of spots, arcs and spirals. We evaluate these differences both qualitatively (by observing the patterns) and quantitatively, through a set of geometric indicators which describe the patterns. The results show that the patterns are history dependent and suggest that published results so far are only a subset of possible patterns. Additionally, the quantitative assessment of pattern properties in time shows that although patterns appear steady, they may indeed be slowly changing over time, while the total biomass and vegetation cover are steady early on. This has implications on the definitions of ecohydrological steady states. We also show that the effects of the idealised initial conditions on model results can be analogous to singular hydrometeorological events, as even stable patterns can be shifted into hybrid patterns by single events. Furthermore, we also explore how the new hybrid patterns compare to the well-established ones in terms of resilience to hydrological perturbations.}, language = {en} } @misc{KhoshBinGhomashCaviedesVoulliemeHinz, author = {Khosh Bin Ghomash, Shahin and Caviedes-Voulli{\`e}me, Daniel and Hinz, Christoph}, title = {Effects of topography and infiltration heterogeneity on surface runoff and connectivity in the Huehnerwasser catchment}, series = {European Geosciences Union, General Assembly 2019, Vienna, Austria, 7-12 April 2019}, journal = {European Geosciences Union, General Assembly 2019, Vienna, Austria, 7-12 April 2019}, address = {Katlenburg-Lindau}, abstract = {The Huehnerwasser catchment is a monitored, early-development constructed catchment within the Lower Lausatia post-mining landscape in Germany. From the initial bare catchment state, a sequence of landscape-forming processes occurred, including erosion-based topographic change and vegetation establishment, which are at the centre of this study. Erosion-based topographic change is strongly driven by surface runoff, while in turn itself also modifying runoff in the catchment. These topographic changes can have a significant impact on the hydrological response of a catchment, as they can affect flow paths, flow speeds and rainfall-runoff-infiltration partitioning, all of which manifest in different ways in runoff hydrographs in response to rainfall events. Vegetation establishment enhances local infiltration capacity, introducing infiltration heterogeneity, thus affecting the topography-controlled flowpaths as water infiltrates at vegetation patches. Critical-zone observatories and monitored early-development systems allow to document signatures of the evolution of catchments and to correlate certain behaviours to processes. However, readily and easily achievable runoff signatures often cannot provide a clear nor full description of process interactions, as the individual roles of processes are stacked together, and strongly shaped by the temporal distribution of rainfall, making it very difficult to disentangle the effects of each process, and making modelling a necessary approach to understand these interactions and their manifestations. All such processes occur at small spatial scales, and are difficult to observe or assess when experimentally studying catchment hydrology. Moreover, given that the complexity of processes contributing to morphological changes and the corresponding alteration of runoff signatures, single catchment experiments and even comprehensive monitoring programmes of whole catchments will neither allow to decipher all processes interactions nor will it allow to apply a statistically derived experimental. In this work, we study the effects that spatial distributions of surface topography and infiltration properties have on surface runoff and surface connectivity in response to single rainfall events, in the context of the Huehnerwasser catchment. We simulate rainfall/runoff processes by means of a physically-based, spatially explicit surface flow model, and assess the results in terms of hydrological signatures (hydrograph, hydrological balance), spatial distribution of the hydrodynamics of runoff, and surface flow connectivity. To do this, we use several DEMs of the H{\"u}hnerwasser catchment recorded during the erosion-based development of the surface (2006-2010), different hypothetical infiltration properties distributions, and a set of different singular rainfall events. The study allows to observe the individual effects that topographic properties and infiltration distributions have on the hydrograph signatures and connect cause-and-effect through an intermediate, conceptual property of the system: surface runoff connectivity, arguably an indicator of hydrological organisation of the runoff response. Moreover, by systematic analysis, the interactions between topography and infiltration can also be assessed in the hydrograph and explained through connectivity. The results show a range of possible magnitudes of influence of topography and infiltration on the runoff response, while highlighting that the onset of runoff and the rising limb of the hydrograph are mostly affected by these features and their interactions, and strongly related to surface runoff connectivity.}, language = {de} } @misc{HinzHafarFischer, author = {Hinz, Christoph and Hafar, Brian and Fischer, Thomas}, title = {Heavy metal mobilisation of salt affected soils and sediments: Assessing the role of chloride complex formation.}, series = {European Geosciences Union, General Assembly 2019, Vienna, Austria, 7-12 April 2019}, journal = {European Geosciences Union, General Assembly 2019, Vienna, Austria, 7-12 April 2019}, address = {Katlenburg-Lindau}, abstract = {Terrestrial and aquatic ecosystems are increasingly exposed to high level of salt (NaCl) concentrations. Impacts of increased salt concentration on mobilisation of heavy metals have been shown for road side soils receiving de-icing salt, for sediments and soils exposed to salt water intrusions, and soils and aquifers receiving runoff from salt mines. In fact, this study was motivated by the impact of salt dumps on soil and groundwater observed for potash mines in the central part of Germany. The objectives of this contribution is to asses the impact of NaCl concentration on heavy metal mobilization using speciation modelling. In particular, we focus on the effect of chloride complex formation in solution and how strongly this complex formation is "extracting" heavy metal cation from soil and sediments substrates. As experimental data for speciation at very high ionic strength is not readily available and not easily measurable, we focus on PHREEQC modelling to assess NaCl concentration ranges up to 3 M, needing to employ Pitzer equation as the activity model. In order to determine the competition of surface reaction and complex formation in aqueous solution, we used three reaction models: i) surface complexation with a high and low affinity site for iron hydroxide, ii) a heterogeneous binding site model for humic acids and iii) ion exchange as described with Rothmund-Kornfeld equation We did a series of simulations for Zn, Cd and Pb. Species distribution for the aqueous phase and the solid surfaces where determined by increasing NaCl solutions for a given total heavy metal concentration. In nearly all simulations conducted, the difference between simulations allowing chloride complexes to form and simulations where complexation is disabled, showed the emergence of a characteristic concentration range of NaCl for which the effect of chloride complexation reaches a maximum. In general, the range of highest sensitivity concerning mobilization occurs within the range of 1-3M NaCl for all simulations. At the lower end of this range shows the highest sensitivity to NaCl changes and is determined by several factors including the affinity to bonding sites and the speciation of an element along the salinity gradient. The peak of this curve is controlled by the point along the salinity gradient where the majority of heavy metal has been mobilized from the surface phase. One important outcome of this study is, that increasing NaCl background concentration behaves in a nonlinear way that is determined by the heterogeneity of the surface binding sites and that there is no simple way of assessing the mobilization potential of chloride complexation in soils and sediments.}, language = {en} } @misc{KhoshBinGhomashCaviedesVoulliemeHinz, author = {Khosh Bin Ghomash, Shahin and Caviedes-Voulli{\`e}me, Daniel and Hinz, Christoph}, title = {Effects of erosion-induced changes to topography on runoff dynamics}, series = {Journal of Hydrology}, volume = {573}, journal = {Journal of Hydrology}, issn = {0022-1694}, doi = {10.1016/j.jhydrol.2019.04.018}, pages = {811 -- 828}, abstract = {Runoff generation from rainfall events is a complex, spatial and temporally dependent process strongly governed, among other factors, by catchment surface topography. Although it is widely known that many catchments experience morphological evolution, it is often ignored in analysis for different reasons ranging from simplification to lack of data. However, young catchments and early landscapes (such as those which are affected by natural or anthropogenic disturbances) do exhibit topography changes which in turn affect catchment hydrodynamics, hydrology and in particular runoff. In this work, we study the runoff generation and hydrodynamics of the H{\"u}hnerwasser artificial catchment (Brandenburg, Germany) during a period of erosion-based topographical changes (2006-2010). Nine Digital Elevation Models from such period were used as topography over which physically-based simulations were performed. The results suggest that topographic evolution in this catchment mostly affects the onset of runoff, whereas peak discharges and receding hydrograph limbs are less affected. These differences in hydrological signatures can be explained through the changes in the spatial distribution of runoff hydrodynamics and their impact on surface runoff connectivity. Relatively small topographical differences produce changing ponding conditions and modify flowpaths which becomes evident only through inspection of the spatial distribution of hydrodynamic variables. Moreover, the study shows that in order for simulations to be able to capture such responses, appropriate computational mesh and topographical data resolution are critical, since connectivity itself can be greatly affected by low resolution data or representation.}, language = {en} }