TY - JOUR
A1 - Zhang, Yan-qiu
A1 - Guo, Zeng-hui
A1 - Chen, Dai-zhao
T1 - Porosity distribution in cyclic dolomites of the Lower Qiulitag Group (Upper Cambrian) in northwestern Tarim Basin, China
JF - China geology
N2 - Increasing interests in hydrocarbon resources at depths have drawn greater attentions to the deeply-buried carbonate reservoirs in the Tarim Basin in China. In this study, the cyclic dolomite rocks of Upper Cambrian Lower Qiulitag Group from four outcrop sections in northwestern Tarim Basin were selected to investigate and evaluate the petrophysical properties in relation to depositional facies and cyclicity. The Lower Qiulitag Group includes ten lithofacies, which were deposited in intermediate to shallow subtidal, restricted shallow subtidal, intertidal, and supratidal environments on a carbonate ramp system. These lithofacies are vertically stacked into repeated shallowing-upward, meter-scale cycles which are further grouped into six third-order depositional sequences (Sq1 to Sq6). There are variable types of pore spaces in the Lower Qiulitag Group dolomite rocks, including interparticle, intraparticle, and fenestral pores of primary origin, inter crystal, and vuggy pores of late diagenetic modification. The porosity in the dolomites is generally facies-selective as that the microbially-originated thrombolites and stromatolites generally yield a relatively high porosity. In contrast, the high-energy ooidal grainstones generally have very low porosity. In this case, the microbialite-based peritidal cycles and peritidal cycle-dominated highstand (or regressive) successions have relatively high volumes of pore spaces, although highly fluctuating (or vertical inhomogeneous). Accordingly, the grainstone-based subtidal cycles and subtidal cycle-dominated transgressive successions generally yield extremely low porosity. This scenario indicates that porosity development and preservation in the thick dolomite successions are primarily controlled by depositional facies which were influenced by sea-level fluctuations of different orders and later diagenetic overprinting.
KW - Dolomites
KW - porosity
KW - cyclicity
KW - Upper Cambrian
KW - stromatolite
KW - microbial
KW - build up
KW - oil-gas basin
KW - oil-gas exploration engineering
KW - Tarim Basin
KW - China
Y1 - 2020
UR - http://en.cgsjournals.com/zgdzdcqkw-data/zgdzyw/2020/3/PDF/cg2020026.pdf
SN - 2096-5192
SN - 2589-9430
VL - 3
IS - 3
SP - 425
EP - 444
PB - Elsevier
CY - Amsterdam
ER -
TY - JOUR
A1 - Dobkowitz, Sophia
A1 - Walz, Ariane
A1 - Baroni, Gabriele
A1 - Pérez-Marin, Aldrin M.
T1 - Cross-Scale Vulnerability Assessment for Smallholder Farming
BT - A Case Study from the Northeast of Brazil
JF - Sustainability
N2 - Climate change heavily impacts smallholder farming worldwide. Cross-scale vulnerability assessment has a high potential to identify nested measures for reducing vulnerability of smallholder farmers. Despite their high practical value, there are currently only limited examples of cross-scale assessments. The presented study aims at assessing the vulnerability of smallholder farmers in the Northeast of Brazil across three scales: regional, farm and field scale. In doing so, it builds on existing vulnerability indices and compares results between indices at the same scale and across scales. In total, six independent indices are tested, two at each scale. The calculated indices include social, economic and ecological indicators, based on municipal statistics, meteorological data, farm interviews and soil analyses. Subsequently, indices and overlapping indicators are normalized for intra- and cross-scale comparison. The results show considerable differences between indices across and within scales. They indicate different activities to reduce vulnerability of smallholder farmers. Major shortcomings arise from the conceptual differences between the indices. We therefore recommend the development of hierarchical indices, which are adapted to local conditions and contain more overlapping indicators for a better understanding of the nested vulnerabilities of smallholder farmers.
KW - family farming
KW - nested vulnerabilities
KW - vulnerability indices
KW - semi-arid regions
KW - Paraíba
Y1 - 2020
U6 - https://doi.org/10.3390/su12093787
SN - 2071-1050
VL - 12
IS - 9
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Scherler, Dirk
A1 - Schwanghart, Wolfgang
T1 - Drainage divide networks - part 1: Identification and ordering in digital elevation models
JF - Earth surface dynamics : ESURF
N2 - We propose a novel way to measure and analyze networks of drainage divides from digital elevation models. We developed an algorithm that extracts drainage divides based on the drainage basin boundaries defined by a stream network. In contrast to streams, there is no straightforward approach to order and classify divides, although it is intuitive that some divides are more important than others. A meaningful way of ordering divides is the average distance one would have to travel down on either side of a divide to reach a common stream location. However, because measuring these distances is computationally expensive and prone to edge effects, we instead sort divide segments based on their tree-like network structure, starting from endpoints at river confluences. The sorted nature of the network allows for assigning distances to points along the divides, which can be shown to scale with the average distance downslope to the common stream location. Furthermore, because divide segments tend to have characteristic lengths, an ordering scheme in which divide orders increase by 1 at junctions mimics these distances. We applied our new algorithm to the Big Tujunga catchment in the San Gabriel Mountains of southern California and studied the morphology of the drainage divide network. Our results show that topographic metrics, like the downstream flow distance to a stream and hillslope relief, attain characteristic values that depend on the drainage area threshold used to derive the stream network. Portions along the divide network that have lower than average relief or are closer than average to streams are often distinctly asymmetric in shape, suggesting that these divides are unstable. Our new and automated approach thus helps to objectively extract and analyze divide networks from digital elevation models.
Y1 - 2020
U6 - https://doi.org/10.5194/esurf-8-245-2020
SN - 2196-6311
SN - 2196-632X
VL - 8
IS - 2
SP - 245
EP - 259
PB - Copernicus Publ.
CY - Göttingen
ER -
TY - JOUR
A1 - Herrero, Mario
A1 - Thornton, Philip K.
A1 - Mason-D'Croz, Daniel
A1 - Palmer, Jeda
A1 - Bodirsky, Benjamin Leon
A1 - Pradhan, Prajal
A1 - Barrett, Christopher B.
A1 - Benton, Tim G.
A1 - Hall, Andrew
A1 - Pikaar, Ilje
A1 - Bogard, Jessica R.
A1 - Bonnett, Graham D.
A1 - Bryan, Brett A.
A1 - Campbell, Bruce M.
A1 - Christensen, Svend
A1 - Clark, Michael
A1 - Fanzo, Jessica
A1 - Godde, Cecile M.
A1 - Jarvis, Andy
A1 - Loboguerrero, Ana Maria
A1 - Mathys, Alexander
A1 - McIntyre, C. Lynne
A1 - Naylor, Rosamond L.
A1 - Nelson, Rebecca
A1 - Obersteiner, Michael
A1 - Parodi, Alejandro
A1 - Popp, Alexander
A1 - Ricketts, Katie
A1 - Smith, Pete
A1 - Valin, Hugo
A1 - Vermeulen, Sonja J.
A1 - Vervoort, Joost
A1 - van Wijk, Mark
A1 - van Zanten, Hannah H. E.
A1 - West, Paul C.
A1 - Wood, Stephen A.
A1 - Rockström, Johan
T1 - Articulating the effect of food systems innovation on the Sustainable Development Goals
JF - The lancet Planetary health
N2 - Food system innovations will be instrumental to achieving multiple Sustainable Development Goals (SDGs). However, major innovation breakthroughs can trigger profound and disruptive changes, leading to simultaneous and interlinked reconfigurations of multiple parts of the global food system. The emergence of new technologies or social solutions, therefore, have very different impact profiles, with favourable consequences for some SDGs and unintended adverse side-effects for others. Stand-alone innovations seldom achieve positive outcomes over multiple sustainability dimensions. Instead, they should be embedded as part of systemic changes that facilitate the implementation of the SDGs. Emerging trade-offs need to be intentionally addressed to achieve true sustainability, particularly those involving social aspects like inequality in its many forms, social justice, and strong institutions, which remain challenging. Trade-offs with undesirable consequences are manageable through the development of well planned transition pathways, careful monitoring of key indicators, and through the implementation of transparent science targets at the local level.
Y1 - 2020
U6 - https://doi.org/10.1016/S2542-5196(20)30277-1
SN - 2542-5196
VL - 5
IS - 1
SP - E50
EP - E62
PB - Elsevier
CY - Oxford
ER -
TY - JOUR
A1 - Koç, Gamze
A1 - Petrow, Theresia
A1 - Thieken, Annegret
T1 - Analysis of the Most Severe Flood Events in Turkey (1960–2014)
BT - Which Triggering Mechanisms and Aggravating Pathways Can be Identified?
JF - Water
N2 - The most severe flood events in Turkey were determined for the period 1960–2014 by considering the number of fatalities, the number of affected people, and the total economic losses as indicators. The potential triggering mechanisms (i.e., atmospheric circulations and precipitation amounts) and aggravating pathways (i.e., topographic features, catchment size, land use types, and soil properties) of these 25 events were analyzed. On this basis, a new approach was developed to identify the main influencing factor per event and to provide additional information for determining the dominant flood occurrence pathways for severe floods. The events were then classified through hierarchical cluster analysis. As a result, six different clusters were found and characterized. Cluster 1 comprised flood events that were mainly influenced by drainage characteristics (e.g., catchment size and shape); Cluster 2 comprised events aggravated predominantly by urbanization; steep topography was identified to be the dominant factor for Cluster 3; extreme rainfall was determined as the main triggering factor for Cluster 4; saturated soil conditions were found to be the dominant factor for Cluster 5; and orographic effects of mountain ranges characterized Cluster 6. This study determined pathway patterns of the severe floods in Turkey with regard to their main causal or aggravating mechanisms. Accordingly, geomorphological properties are of major importance in large catchments in eastern and northeastern Anatolia. In addition, in small catchments, the share of urbanized area seems to be an important factor for the extent of flood impacts. This paper presents an outcome that could be used for future urban planning and flood risk prevention studies to understand the flood mechanisms in different regions of Turkey.
KW - hierarchical clustering
KW - Hess-Brezowsky Großwetterlagen classification
KW - ERA5
KW - flood hazards
KW - pathway
KW - Turkey
Y1 - 2020
U6 - https://doi.org/10.3390/w12061562
SN - 2073-4441
VL - 12
IS - 6
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Laudan, Jonas
A1 - Zöller, Gert
A1 - Thieken, Annegret
T1 - Flash floods versus river floods
BT - a comparison of psychological impacts and implications for precautionary behaviour
JF - Natural Hazards and Earth System Sciences
N2 - River floods are among the most damaging natural hazards that frequently occur in Germany. Flooding causes high economic losses and impacts many residents. In 2016, several southern German municipalities were hit by flash floods after unexpectedly severe heavy rainfall, while in 2013 widespread river flooding had occurred. This study investigates and compares the psychological impacts of river floods and flash floods and potential consequences for precautionary behaviour. Data were collected using computer-aided telephone interviews that were conducted among flood-affected households around 9 months after each damaging event. This study applies Bayesian statistics and negative binomial regressions to test the suitability of psychological indicators to predict the precaution motivation of individuals. The results show that it is not the particular flood type but rather the severity and local impacts of the event that are crucial for the different, and potentially negative, impacts on mental health. According to the used data, however, predictions of the individual precaution motivation should not be based on the derived psychological indicators – i.e. coping appraisal, threat appraisal, burden and evasion – since their explanatory power was generally low and results are, for the most part, non-significant. Only burden reveals a significant positive relation to planned precaution regarding weak flash floods. In contrast to weak flash floods and river floods, the perceived threat of strong flash floods is significantly lower although feelings of burden and lower coping appraisals are more pronounced. Further research is needed to better include psychological assessment procedures and to focus on alternative data sources regarding floods and the connected precaution motivation of affected residents.
KW - private households
KW - risk perceptions
KW - extreme rainfall
KW - health
KW - mitigation
KW - Germany
KW - people
KW - damage
KW - preparedness
KW - residents
Y1 - 2019
U6 - https://doi.org/10.5194/nhess-20-999-2020
SN - 1684-9981
VL - 20
SP - 999
EP - 1023
PB - European Geophysical Society
CY - Katlenburg-Lindau
ER -
TY - JOUR
A1 - Hudson, Paul
A1 - Pham, My
A1 - Hagedoorn, Liselotte
A1 - Thieken, Annegret
A1 - Lasage, Ralph
A1 - Bubeck, Philip
T1 - Self-stated recovery from flooding
BT - empirical results from a survey in Central Vietnam
JF - Journal of Flood Risk Management
N2 - Social inequalities lead to flood resilience inequalities across social groups, a topic that requires improved documentation and understanding. The objective of this paper is to attend to these differences by investigating self-stated flood recovery across genders in Vietnam as a conceptual replication of earlier results from Germany. This study employs a regression-based analysis of 1,010 respondents divided between a rural coastal and an urban community in Thua Thien-Hue province. The results highlight an important set of recovery process-related variables. The set of relevant variables is similar across genders in terms of inclusion and influence, and includes age, social capital, internal and external support after a flood, perceived severity of previous flood impacts, and the perception of stress-resilience. However, women were affected more heavily by flooding in terms of longer recovery times, which should be accounted for in risk management. Overall, the studied variables perform similarly in Vietnam and Germany. This study, therefore, conceptually replicates previous results suggesting that women display slightly slower recovery levels as well as that psychological variables influence recovery rates more than adverse flood impacts. This provides an indication of the results' potentially robust nature due to the different socio-environmental contexts in Germany and Vietnam.
KW - flood recovery
KW - resilience
KW - societal equity
KW - vulnerability
Y1 - 2020
U6 - https://doi.org/10.1111/jfr3.12680
SN - 1753-318X
VL - 14
PB - Wiley-Blackwell
CY - Oxford
ER -
TY - JOUR
A1 - Jehmlich, Caroline
A1 - Hudson, Paul
A1 - Thieken, Annegret
T1 - Short contribution on adaptive behaviour of flood-prone companies
BT - a pilot study of Dresden-Laubegast, Germany
JF - Journal of Flood Risk Management
N2 - Integrated flood management strategies consider property-level precautionary measures as a vital part. Whereas this is a well-researched topic for residents, little is known about the adaptive behaviour of flood-prone companies although they often settle on the ground floor of buildings and are thus among the first affected by flooding. This pilot study analyses flood responses of 64 businesses in a district of the city of Dresden, Germany that experienced major flooding in 2002 and 2013. Using standardised survey data and accompanying qualitative interviews, the analyses revealed that the largest driver of adaptive behaviour is experiencing flood events. Intangible factors such as tradition and a sense of community play a role for the decision to stay in the area, while lacking ownership might hamper property-level adaptation. Further research is also needed to understand the role of insurance and governmental aid for recovery and adaptation of businesses.
KW - adaptation
KW - disaster risk reduction
KW - integrated flood risk management
KW - risk perception
Y1 - 2019
U6 - https://doi.org/10.1111/jfr3.12653
SN - 1753-318X
VL - 13
PB - Wiley-Blackwell
CY - Oxford
ER -
TY - JOUR
A1 - Koc, Gamze
A1 - Petrow, Theresia
A1 - Thieken, Annegret
T1 - Analysis of the most severe flood events in Turkey (1960-2014)
BT - which triggering mechanisms and aggravating pathways can be identified?
JF - Water / Molecular Diversity Preservation International (MDPI)
N2 - The most severe flood events in Turkey were determined for the period 1960-2014 by considering the number of fatalities, the number of affected people, and the total economic losses as indicators. The potential triggering mechanisms (i.e., atmospheric circulations and precipitation amounts) and aggravating pathways (i.e., topographic features, catchment size, land use types, and soil properties) of these 25 events were analyzed. On this basis, a new approach was developed to identify the main influencing factor per event and to provide additional information for determining the dominant flood occurrence pathways for severe floods. The events were then classified through hierarchical cluster analysis. As a result, six different clusters were found and characterized. Cluster 1 comprised flood events that were mainly influenced by drainage characteristics (e.g., catchment size and shape); Cluster 2 comprised events aggravated predominantly by urbanization; steep topography was identified to be the dominant factor for Cluster 3; extreme rainfall was determined as the main triggering factor for Cluster 4; saturated soil conditions were found to be the dominant factor for Cluster 5; and orographic effects of mountain ranges characterized Cluster 6. This study determined pathway patterns of the severe floods in Turkey with regard to their main causal or aggravating mechanisms. Accordingly, geomorphological properties are of major importance in large catchments in eastern and northeastern Anatolia. In addition, in small catchments, the share of urbanized area seems to be an important factor for the extent of flood impacts. This paper presents an outcome that could be used for future urban planning and flood risk prevention studies to understand the flood mechanisms in different regions of Turkey.
KW - hierarchical clustering
KW - Hess-Brezowsky Grosswetterlagen classification
KW - ERA5
KW - flood hazards
KW - pathway
KW - Turkey
Y1 - 2020
U6 - https://doi.org/10.3390/w12061562
SN - 2073-4441
VL - 12
IS - 6
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Kellermann, Patric
A1 - Schröter, Kai
A1 - Thieken, Annegret
A1 - Haubrock, Sören-Nils
A1 - Kreibich, Heidi
T1 - The object-specific flood damage database HOWAS 21
JF - Natural hazards and earth system sciences
N2 - The Flood Damage Database HOWAS 21 contains object-specific flood damage data resulting from fluvial, pluvial and groundwater flooding. The datasets incorporate various variables of flood hazard, exposure, vulnerability and direct tangible damage at properties from several economic sectors. The main purpose of development of HOWAS 21 was to support forensic flood analysis and the derivation of flood damage models. HOWAS 21 was first developed for Germany and currently almost exclusively contains datasets from Germany. However, its scope has recently been enlarged with the aim to serve as an international flood damage database; e.g. its web application is now available in German and English. This paper presents the recent advancements of HOWAS 21 and highlights exemplary analyses to demonstrate the use of HOWAS 21 flood damage data. The data applications indicate a large potential of the database for fostering a better understanding and estimation of the consequences of flooding.
Y1 - 2020
U6 - https://doi.org/10.5194/nhess-20-2503-2020
SN - 1561-8633
SN - 1684-9981
VL - 20
IS - 9
SP - 2503
EP - 2519
PB - Copernicus
CY - Göttingen
ER -
TY - JOUR
A1 - Pradhan, Prajal
A1 - Kropp, Jürgen
T1 - Interplay between diets, health, and climate change
JF - Sustainability
N2 - The world is facing a triple burden of undernourishment, obesity, and environmental impacts from agriculture while nourishing its population. This burden makes sustainable nourishment of the growing population a global challenge. Addressing this challenge requires an understanding of the interplay between diets, health, and associated environmental impacts (e.g., climate change). For this, we identify 11 typical diets that represent dietary habits worldwide for the last five decades. Plant-source foods provide most of all three macronutrients (carbohydrates, protein, and fat) in developing countries. In contrast, animal-source foods provide a majority of protein and fat in developed ones. The identified diets deviate from the recommended healthy diet with either too much (e.g., red meat) or too little (e.g., fruits and vegetables) food and nutrition supply. The total calorie supplies are lower than required for two diets. Sugar consumption is higher than recommended for five diets. Three and five diets consist of larger-than-recommended carbohydrate and fat shares, respectively. Four diets with a large share of animal-source foods exceed the recommended value of red meat. Only two diets consist of at least 400 gm/cap/day of fruits and vegetables while accounting for food waste. Prevalence of undernourishment and underweight dominates in the diets with lower calories. In comparison, a higher prevalence of obesity is observed for diets with higher calories with high shares of sugar, fat, and animal-source foods. However, embodied emissions in the diets do not show a clear relation with calorie supplies and compositions. Two high-calorie diets embody more than 1.5 t CO2eq/cap/yr, and two low-calorie diets embody around 1 t CO2eq/cap/yr. Our analysis highlights that sustainable and healthy diets can serve the purposes of both nourishing the population and, at the same time, reducing the environmental impacts of agriculture.
KW - dietary patterns
KW - healthy diets
KW - embodied emissions
KW - diet shifts
KW - sustainable diets
KW - emission intensity
Y1 - 2020
U6 - https://doi.org/10.3390/su12093878
SN - 2071-1050
VL - 12
IS - 9
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Vyse, Stuart Andrew
A1 - Semiromi, Majid Taie
A1 - Lischeid, Gunnar
A1 - Merz, Christoph
T1 - Characterizing hydrological processes within kettle holes using stable water isotopes in the Uckermark of northern Brandenburg, Germany
JF - Hydrological Processes
N2 - Understanding the hydrologic connectivity between kettle holes and shallow groundwater, particularly in reaction to the highly variable local meteorological conditions, is of paramount importance for tracing water in a hydro(geo)logically complex landscape and thus for integrated water resource management. This article is aimed at identifying the dominant hydrological processes affecting the kettle holes' water balance and their interactions with the shallow groundwater domain in the Uckermark region, located in the north-east of Germany. For this reason, based on the stable isotopes of oxygen (delta O-18) and hydrogen (delta H-2), an isotopic mass balance model was employed to compute the evaporative loss of water from the kettle holes from February to August 2017. Results demonstrated that shallow groundwater inflow may play the pivotal role in the processes taking part in the hydrology of the kettle holes in the Uckermark region. Based on the calculated evaporation/inflow (E/I) ratios, most of the kettle holes (86.7%) were ascertained to have a partially open, flow-through-dominated system. Moreover, we identified an inverse correlation between E/I ratios and the altitudes of the kettle holes. The same holds for electrical conductivity (EC) and the altitudes of the kettle holes. In accordance with the findings obtained from this study, a conceptual model explaining the interaction between the shallow groundwater and the kettle holes of Uckermark was developed. The model exhibited that across the highest altitudes, the recharge kettle holes are dominant, where a lower ratio of E/I and a lower EC was detected. By contrast, the lowest topographical depressions represent the discharge kettle holes, where a higher ratio of E/I and EC could be identified. The kettle holes existing in between were categorized as flow-through kettle holes through which the recharge takes place from one side and discharge from the other side.
KW - evaporation
KW - groundwater inflow
KW - kettle hole
KW - stable water isotope
KW - surface–groundwater interactions
Y1 - 2020
U6 - https://doi.org/10.1002/hyp.13699
SN - 0885-6087
SN - 1099-1085
VL - 34
IS - 8
SP - 1868
EP - 1887
PB - Wiley
CY - New York
ER -
TY - JOUR
A1 - Smetanová, Anna
A1 - Müller, Anne
A1 - Zargar, Morteza
A1 - Suleiman, Mohamed A.
A1 - Gholami, Faraz Rabei
A1 - Mousavi, Maryam
T1 - Mesoscale mapping of sediment source hotspots for dam sediment management in data-sparse semi-arid catchments
JF - Water
N2 - Land degradation and water availability in semi-arid regions are interdependent challenges for management that are influenced by climatic and anthropogenic changes. Erosion and high sediment loads in rivers cause reservoir siltation and decrease storage capacity, which pose risk on water security for citizens, agriculture, and industry. In regions where resources for management are limited, identifying spatial-temporal variability of sediment sources is crucial to decrease siltation. Despite widespread availability of rigorous methods, approaches simplifying spatial and temporal variability of erosion are often inappropriately applied to very data sparse semi-arid regions. In this work, we review existing approaches for mapping erosional hotspots, and provide an example of spatial-temporal mapping approach in two case study regions. The barriers limiting data availability and their effects on erosion mapping methods, their validation, and resulting prioritization of leverage management areas are discussed.
KW - reservoir siltation
KW - water security
KW - water management
KW - data sharing
KW - spatial-temporal
KW - erosion hotspots
KW - mapping
KW - global datasets
KW - mesoscale
KW - leverage areas
Y1 - 2020
U6 - https://doi.org/10.3390/w12020396
SN - 2073-4441
VL - 12
IS - 2
SP - 1
EP - 24
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Mtilatila, Lucy Mphatso Ng'ombe
A1 - Bronstert, Axel
A1 - Shrestha, Pallav
A1 - Kadewere, Peter
A1 - Vormoor, Klaus Josef
T1 - Susceptibility of water resources and hydropower production to climate change in the tropics
BT - the case of Lake Malawi and Shire River Basins, SE Africa
JF - Hydrology : open access journal
N2 - The sensitivity of key hydrologic variables and hydropower generation to climate change in the Lake Malawi and Shire River basins is assessed. 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. 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. An annual temperature increase of 1 degrees 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 in the 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 degrees C (3.5 degrees 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 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, e.g., longer low flow periods and/or higher discharge fluctuations, and thus uncertainty in the amount of electricity produced.
KW - Lake Malawi Basin
KW - Shire River Basin
KW - lake water balance
KW - climate change impacts in the tropics
KW - hydropower generation
KW - response surface analysis
KW - sensitivity analysis
Y1 - 2020
U6 - https://doi.org/10.3390/hydrology7030054
SN - 2306-5338
VL - 7
IS - 3
PB - MDPI
CY - Basel
ER -
TY - JOUR
A1 - Rottler, Erwin
A1 - Francke, Till
A1 - Bürger, Gerd
A1 - Bronstert, Axel
T1 - Long-term changes in central European river discharge for 1869–2016
BT - impact of changing snow covers, reservoir constructions and an intensified hydrological cycle
JF - Hydrology and Earth System Sciences
N2 - Recent climatic changes have the potential to severely alter river runoff, particularly in snow-dominated river basins. Effects of changing snow covers superimpose with changes in precipitation and anthropogenic modifications of the watershed and river network. In the attempt to identify and disentangle long-term effects of different mechanisms, we employ a set of analytical tools to extract long-term changes in river runoff at high resolution. We combine quantile sampling with moving average trend statistics and empirical mode decomposition and apply these tools to discharge data recorded along rivers with nival, pluvial and mixed flow regimes as well as temperature and precipitation data covering the time frame 1869-2016. With a focus on central Europe, we analyse the long-term impact of snow cover and precipitation changes along with their interaction with reservoir constructions.
Our results show that runoff seasonality of snow-dominated rivers decreases. Runoff increases in winter and spring, while discharge decreases in summer and at the beginning of autumn. We attribute this redistribution of annual flow mainly to reservoir constructions in the Alpine ridge. During the course of the last century, large fractions of the Alpine rivers were dammed to produce hydropower. In recent decades, runoff changes induced by reservoir constructions seem to overlap with changes in snow cover. We suggest that Alpine signals propagate downstream and affect runoff far outside the Alpine area in river segments with mixed flow regimes. Furthermore, our results hint at more (intense) rain-fall in recent decades. Detected increases in high discharge can be traced back to corresponding changes in precipitation.
KW - empirical mode decomposition
KW - atmospheric blocking
KW - heavy precipitation
KW - streamflow trends
KW - climate-change
KW - rhine basin
KW - time-series
KW - events
KW - Switzerland
KW - variability
Y1 - 2020
U6 - https://doi.org/10.5194/hess-24-1721-2020
SN - 1027-5606
SN - 1607-7938
VL - 24
IS - 4
SP - 1721
EP - 1740
PB - Copernicus
CY - Göttingen
ER -
TY - JOUR
A1 - Jing, Miao
A1 - Kumar, Rohini
A1 - Heße, Falk
A1 - Thober, Stephan
A1 - Rakovec, Oldrich
A1 - Samaniego, Luis
A1 - Attinger, Sabine
T1 - Assessing the response of groundwater quantity and travel time distribution to 1.5, 2, and 3 °C global warming in a mesoscale central German basin
JF - Hydrology and Earth System Sciences
N2 - Groundwater is the biggest single source of high-quality freshwater worldwide, which is also continuously threatened by the changing climate. In this paper, we investigate the response of the regional groundwater system to climate change under three global warming levels (1.5, 2, and 3 ∘C) in a central German basin (Nägelstedt). This investigation is conducted by deploying an integrated modeling workflow that consists of a mesoscale hydrologic model (mHM) and a fully distributed groundwater model, OpenGeoSys (OGS). mHM is forced with climate simulations of five general circulation models under three representative concentration pathways. The diffuse recharges estimated by mHM are used as boundary forcings to the OGS groundwater model to compute changes in groundwater levels and travel time distributions. Simulation results indicate that groundwater recharges and levels are expected to increase slightly under future climate scenarios. Meanwhile, the mean travel time is expected to decrease compared to the historical average. However, the ensemble simulations do not all agree on the sign of relative change. Changes in mean travel time exhibit a larger variability than those in groundwater levels. The ensemble simulations do not show a systematic relationship between the projected change (in both groundwater levels and travel times) and the warming level, but they indicate an increased variability in projected changes with adjusting the enhanced warming level from 1.5 to 3 ∘C. Correspondingly, it is highly recommended to restrain the trend of global warming.
KW - climate change impacts
KW - hydrological models
KW - coupled surface
KW - water fluxes
KW - catchment
KW - recharge
KW - dynamics
KW - aquifer
KW - flow
KW - parameterization
Y1 - 2020
U6 - https://doi.org/10.5194/hess-24-1511-2020
SN - 1607-7938
SN - 1027-5606
VL - 24
IS - 3
SP - 1511
EP - 1526
PB - Copernicus Publ.
CY - Göttingen
ER -
TY - JOUR
A1 - Schmidt, Lennart
A1 - Heße, Falk
A1 - Attinger, Sabine
A1 - Kumar, Rohini
T1 - Challenges in applying machine learning models for hydrological inference: a case study for flooding events across Germany
JF - Water Resources Research
N2 - Machine learning (ML) algorithms are being increasingly used in Earth and Environmental modeling studies owing to the ever-increasing availability of diverse data sets and computational resources as well as advancement in ML algorithms. Despite advances in their predictive accuracy, the usefulness of ML algorithms for inference remains elusive. In this study, we employ two popular ML algorithms, artificial neural networks and random forest, to analyze a large data set of flood events across Germany with the goals to analyze their predictive accuracy and their usability to provide insights to hydrologic system functioning. The results of the ML algorithms are contrasted against a parametric approach based on multiple linear regression. For analysis, we employ a model-agnostic framework named Permuted Feature Importance to derive the influence of models' predictors. This allows us to compare the results of different algorithms for the first time in the context of hydrology. Our main findings are that (1) the ML models achieve higher prediction accuracy than linear regression, (2) the results reflect basic hydrological principles, but (3) further inference is hindered by the heterogeneity of results across algorithms. Thus, we conclude that the problem of equifinality as known from classical hydrological modeling also exists for ML and severely hampers its potential for inference. To account for the observed problems, we propose that when employing ML for inference, this should be made by using multiple algorithms and multiple methods, of which the latter should be embedded in a cross-validation routine.
KW - machine learning
KW - inference
KW - floods
Y1 - 2019
VL - 56
IS - 5
PB - John Wiley & Sons, Inc.
CY - New Jersey
ER -
TY - JOUR
A1 - Bilbao-Lasa, Peru
A1 - Jara Muñoz, Julius
A1 - Pedoja, Kevin
A1 - Álvarez, Irantzu
A1 - Aranburu, Arantza
A1 - Iriarte, Eneko
A1 - Galparsoro, Ibon
T1 - Submerged marine terraces identification and an approach for numerical modeling the sequence formation in the Bay of Biscay (Northeastern Iberian Peninsula)
JF - Frontiers in Earth Science
N2 - Submerged sequences of marine terraces potentially provide crucial information of past sea-level positions. However, the distribution and characteristics of drowned marine terrace sequences are poorly known at a global scale. Using bathymetric data and novel mapping and modeling techniques, we studied a submerged sequence of marine terraces in the Bay of Biscay with the objective to identify the distribution and morphologies of submerged marine terraces and the timing and conditions that allowed their formation and preservation. To accomplish the objectives a high-resolution bathymetry (5 m) was analyzed using Geographic Information Systems and TerraceM(R). The successive submerged terraces were identified using a Surface Classification Model, which linearly combines the slope and the roughness of the surface to extract fossil sea-cliffs and fossil rocky shore platforms. For that purpose, contour and hillshaded maps were also analyzed. Then, shoreline angles, a geomorphic marker located at the intersection between the fossil sea-cliff and platform, were mapped analyzing swath profiles perpendicular to the isobaths. Most of the submerged strandlines are irregularly preserved throughout the continental shelf. In summary, 12 submerged terraces with their shoreline angles between approximately: -13 m (T1), -30 and -32 m (T2), -34 and 41 m (T3), -44 and -47 m (T4), -49 and 53 m (T5), -55 and 58 m (T6), -59 and 62 m (T7), -65 and 67 m (T8), -68 and 70 m (T9), -74 and -77 m (T10), -83 and -86 m (T11) and -89 and 92 m (T12). Nevertheless, the ones showing the best lateral continuity and preservation in the central part of the shelf are T3, T4, T5, T7, T8, and T10. The age of the terraces has been estimated using a landscape evolution model. To simulate the formation and preservation of submerged terraces three different scenarios: (i) 20-0 ka; (ii) 128-0 ka; and (iii) 128-20 ka, were compared. The best scenario for terrace generation was between 128 and 20 Ka, where T3, T5, and T7 could have been formed.
KW - marine terrace
KW - submerged sequence
KW - digital bathymetric model
KW - TerraceM
KW - numerical modeling
KW - Bay of Biscay
Y1 - 2020
U6 - https://doi.org/10.3389/feart.2020.00047
SN - 2296-6463
VL - 8
IS - 47
SP - 1
EP - 20
PB - Frontiers Media
CY - Lausanne
ER -
TY - JOUR
A1 - Metin, Ayse Duha
A1 - Dung, Nguyen Viet
A1 - Schröter, Kai
A1 - Vorogushyn, Sergiy
A1 - Guse, Björn
A1 - Kreibich, Heidi
A1 - Merz, Bruno
T1 - The role of spatial dependence for large-scale flood risk estimation
JF - Natural hazards and earth system sciences
N2 - Flood risk assessments are typically based on scenarios which assume homogeneous return periods of flood peaks throughout the catchment. This assumption is unrealistic for real flood events and may bias risk estimates for specific return periods. We investigate how three assumptions about the spatial dependence affect risk estimates: (i) spatially homogeneous scenarios (complete dependence), (ii) spatially heterogeneous scenarios (modelled dependence) and (iii) spatially heterogeneous but uncorrelated scenarios (complete independence). To this end, the model chain RFM (regional flood model) is applied to the Elbe catchment in Germany, accounting for the spatio-temporal dynamics of all flood generation processes, from the rainfall through catchment and river system processes to damage mechanisms. Different assumptions about the spatial dependence do not influence the expected annual damage (EAD); however, they bias the risk curve, i.e. the cumulative distribution function of damage. The widespread assumption of complete dependence strongly overestimates flood damage of the order of 100% for return periods larger than approximately 200 years. On the other hand, for small and medium floods with return periods smaller than approximately 50 years, damage is underestimated. The overestimation aggravates when risk is estimated for larger areas. This study demonstrates the importance of representing the spatial dependence of flood peaks and damage for risk assessments.
Y1 - 2020
U6 - https://doi.org/10.5194/nhess-20-967-2020
SN - 1561-8633
SN - 1684-9981
VL - 20
IS - 4
SP - 967
EP - 979
PB - European Geosciences Union (EGU) ; Copernicus
CY - Göttingen
ER -
TY - JOUR
A1 - Ramachandran, Srikanthan
A1 - Rupakheti, Maheswar
A1 - Lawrence, Mark
T1 - Aerosol-induced atmospheric heating rate decreases over South and East Asia as a result of changing content and composition
JF - Scientific reports
N2 - Aerosol emissions from human activities are extensive and changing rapidly over Asia. Model simulations and satellite observations indicate a dipole pattern in aerosol emissions and loading between South Asia and East Asia, two of the most heavily polluted regions of the world. We examine the previously unexplored diverging trends in the existing dipole pattern of aerosols between East and South Asia using the high quality, two-decade long ground-based time series of observations of aerosol properties from the Aerosol Robotic Network (AERONET), from satellites (Moderate Resolution Imaging Spectroradiometer (MODIS) and Ozone Monitoring Instrument (OMI)), and from model simulations (Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2). The data cover the period since 2001 for Kanpur (South Asia) and Beijing (East Asia), two locations taken as being broadly representative of the respective regions. Since 2010 a dipole in aerosol optical depth (AOD) is maintained, but the trend is reversed-the decrease in AOD over Beijing (East Asia) is rapid since 2010, being 17% less in current decade compared to first decade of twenty-first century, while the AOD over South Asia increased by 12% during the same period. Furthermore, we find that the aerosol composition is also changing over time. The single scattering albedo (SSA), a measure of aerosol's absorption capacity and related to aerosol composition, is slightly higher over Beijing than Kanpur, and has increased from 0.91 in 2002 to 0.93 in 2017 over Beijing and from 0.89 to 0.92 during the same period over Kanpur, confirming that aerosols in this region have on an average become more scattering in nature. These changes have led to a notable decrease in aerosol-induced atmospheric heating rate (HR) over both regions between the two decades, decreasing considerably more over East Asia (- 31%) than over South Asia (- 9%). The annual mean HR is lower now, it is still large (>= 0.6 K per day), which has significant climate implications. The seasonal trends in AOD, SSA and HR are more pronounced than their respective annual trends over both regions. The seasonal trends are caused mainly by the increase/decrease in anthropogenic aerosol emissions (sulfate, black carbon and organic carbon) while the natural aerosols (dust and sea salt) did not change significantly over South and East Asia during the last two decades. The MERRA-2 model is able to simulate the observed trends in AODs well but not the magnitude, while it also did not simulate the SSA values or trends well. These robust findings based on observations of key aerosol parameters and previously unrecognized diverging trends over South and East Asia need to be accounted for in current state-of-the-art climate models to ensure accurate quantification of the complex and evolving impact of aerosols on the regional climate over Asia.
Y1 - 2020
U6 - https://doi.org/10.1038/s41598-020-76936-z
SN - 2045-2322
VL - 10
IS - 1
PB - Macmillan Publishers Limited, part of Springer Nature
CY - [London]
ER -