Non‐stationary hydrological model parameters: a framework based on SOM‐B

The application of stationary parameters in conceptual hydrological models, even under changing boundary conditions, is a common yet unproven practice. This study investigates the impact of non‐stationary model parameters on model performance for different flow indices and time scales. Therefore, a Self‐Organizing Map based optimization approach, which links non‐stationary model parameters with climate indices, is presented and tested on seven meso‐scale catchments in northern Germany. The algorithm automatically groups sub‐periods with similar climate characteristics and allocates them to similar model parameter sets. The climate indices used for the classification of sub‐periods are based on (a) yearly means and (b) a moving average over the previous 61 days. Classification b supports the estimation of continuous non‐stationary parameters. The results show that (i) non‐stationary model parameters can improve the performance of hydrological models with an acceptable growth in parameter uncertainty; (ii) some model parameters are highly correlated to some climate indices; (iii) the model performance improves more for monthly means than yearly means; and (iv) in general low to medium flows improve more than high flows. It was further shown how the gained knowledge can be used to identify insufficiencies in the model structure. Copyright © 2015 John Wiley & Sons, Ltd.     

Spatio‐temporal controls of snowmelt and runoff generation during rain‐on‐snow events in a mid‐latitude mountain catchment

A network of 30 standalone snow monitoring stations was used to investigate the snow cover distribution, snowmelt dynamics, and runoff generation during two rain‐on‐snow (ROS) events in a 40 km² montane catchment in the Black Forest region of southwestern Germany. A multiple linear regression analysis using elevation, aspect, and land cover as predictors for the snow water equivalent (SWE) distribution within the catchment was applied on an hourly basis for two significant ROS flood events that occurred in December 2012. The available snowmelt water, liquid precipitation, as well as the total retention storage of the snow cover were considered in order to estimate the amount of water potentially available for the runoff generation. The study provides a spatially and temporally distributed picture of how the two observed ROS floods developed in the catchment. It became evident that the retention capacity of the snow cover is a crucial mechanism during ROS. It took several hours before water was released from the snowpack during the first ROS event, while retention storage was exceeded within 1 h from the start of the second event. Elevation was the most important terrain feature. South‐facing terrain contributed more water for runoff than north‐facing slopes, and only slightly more runoff was generated at open compared to forested areas. The results highlight the importance of snowmelt together with liquid precipitation for the generation of flood runoff during ROS and the large temporal and spatial variability of the relevant processes. Copyright © 2015 John Wiley & Sons, Ltd.     

Internal catchment process simulation in a snow‐dominated basin: performance evaluation with spatiotemporally variable runoff generation and groundwater dynamics

Hydrologic models have increasingly been used in forest hydrology to overcome the limitations of paired watershed experiments, where vegetative recovery and natural variability obscure the inferences and conclusions that can be drawn from such studies. Models are also plagued by uncertainty, however, and parameter equifinality is a common concern. Physically‐based, spatially‐distributed hydrologic models must therefore be tested with high‐quality experimental data describing a multitude of concurrent internal catchment processes under a range of hydrologic regimes. This study takes a novel approach by not only examining the ability of a pre‐calibrated model to realistically simulate watershed outlet flows over a four year period, but a multitude of spatially‐extensive, internal catchment process observations not previously evaluated, including: continuous groundwater dynamics, instantaneous stream and road network flows, and accumulation and melt period spatial snow distributions. Many hydrologic model evaluations are only on the comparison of predicted and observed discharge at a catchment outlet and remain in the ‘infant stage’ in terms of model testing. This study, on the other hand, tests the internal spatial predictions of a distributed model with a range of field observations over a wide range of hydroclimatic conditions. Nash‐Sutcliffe model efficiency was improved over prior evaluations due to continuing efforts in improving the quality of meteorological data collection. Road and stream network flows were generally well simulated for a range of hydrologic conditions, and snowpack spatial distributions were well simulated for one of two years examined. The spatial variability of groundwater dynamics was effectively simulated, except at locations where strong stream–groundwater interactions exist. Model simulations overall were quite successful in realistically simulating the spatiotemporal variability of internal catchment processes in the watershed, but the premature onset of simulated snowmelt for one of the simulation years has prompted further work in model development. Copyright © 2011 John Wiley & Sons, Ltd.     

Polybrominated diphenyl ethers and their hydroxylated/methoxylated analogs: environmental sources, metabolic relationships, and relative toxicities

Brominated compounds are ubiquitous in the aquatic environment. The polybrominated diphenyl ether (PBDE) flame retardants are anthropogenic compounds of concern. Studies suggest that PBDEs can be biotransformed to hydroxylated brominated diphenyl ethers (OH-BDE). However, the rate of OH-BDE formation observed has been extremely small. OH-BDEs have also been identified as natural compounds produced by some marine invertebrates. Another class of compounds, the methoxylated BDEs (MeO-BDEs), has also been identified as natural compounds in the marine environment. Both the OH-BDEs and MeO-BDEs bioaccumulate in higher marine organisms. Recent studies have demonstrated that MeO-BDEs can be biotransformed to OH-BDEs and this generates greater amounts of OH-BDEs than could be generated from PBDEs. Consequently, MeO-BDEs likely represent the primary source of metabolically derived OH-BDEs. Given that for some endpoints OH-BDEs often exhibit greater toxicity compared to PBDEs, it is prudent to consider OH-BDEs as chemicals of concern, despite their seemingly "natural" origins.     

A Mediterranean earthquake project

Cumulative frequency and cumulative energy may vary from one sample of earthquakes to another either in the same or in the opposite sense. Conditions for the variations are deduced theoretically and illustrated by numerical examples.     

A tectono-stratigraphic record of an extensional basin: the Lower Jurassic Ab-Haji Formation of east-central Iran

The Lower Jurassic Ab-Haji Formation consists of siliciclastic strata which are widespread and superbly exposed across the Tabas and Lut blocks of east-central Iran. The formation records the geodynamic history of central Iran during the Early Jurassic in the aftermath of the main Cimmerian event (near the Triassic–Jurassic boundary) through its sedimentary facies and stratigraphic architecture and allows palaeogeographic and palaeoenvironmental reconstructions. We measured and studied three well-exposed outcrop sections and identified lithofacies and facies associations (fluvial plain, delta plain, delta front, prodelta, and shallow-marine siliciclastic shelf). The integration of all geological, stratigraphic, and sedimentological data shows a west-to-east continental-to-marine gradient within the Ab-Haji Formation. Based on thickness variations, lateral facies changes, palaeocurrent patterns, and changes in the nature of the basal contact of the Ab-Haji Formation on the Tabas and Lut blocks, we locate the fault-bounded Yazd Block in the west and the Shotori Swell at the eastern edge of the Tabas Block as provenance regions. The pattern of thickness variations, rapid east–west facies changes, and provenance is best explained by a tectonic model invoking large tilted fault blocks in an extensional basin. The basal unit shows distinct increase in grain size at the base of the Ab-Haji Formation, similar to the Shemshak Group of the Alborz Mountains (the base of the Alasht Formation) and the non-marine time-equivalent succession of the Binalud Mountains of northeastern Iran. This grain size pattern may have been caused by rapid source area uplift due to slab break-off of the subducted Iran plate in the course of the Cimmerian collision in east-central Iran.     

Carbonation of lignite fly ash at ambient T and P in a semi-dry reaction system for CO2 sequestration

The global rise in atmospheric greenhouse gas concentrations calls for practicable solutions to capture CO₂. In this study, a mineral carbonation process was applied in which CO₂ reacts with alkaline lignite ash and forms stable carbonate solids. In comparison to previous studies, the assays were conducted at low temperatures and pressures and under semi-dry reaction conditions in an 8 L laboratory mixing device. In order to find optimum process conditions the pCO₂ (10-20%), stirring rate (500-3000 rpm) and the liquid to solid ratio (L/S = 0.03-0.36 L kg⁻¹) were varied. In all experiments a considerable CO₂ uptake from the gas phase was observed. Concurrently the solid phase contents of Ca and Mg (hydr)oxides decreased and CaCO₃ and MgCO₃ fractions increased throughout the experiments, showing that CO₂ was stabilized as a solid carbonate. The carbonation reaction depends on three factors: Dissolution of CO₂ in the liquid phase, mobilization of Ca and Mg from the mineral surface and precipitation of the carbonate solids. Those limitations were found to depend strongly on the variation of the process parameters. Optimum reaction conditions could be found for L/S ratios between 0.12 and 0.18, medium stirring velocities and pCO₂ between 10% and 20%.Maximum CO₂ uptake by the solid phase was 4.8 mmol g⁻¹ after 120 min, corresponding to a carbonation efficiency for the alkaline material of 53% of the theoretical CO₂ binding capacity. In comparison to previous studies both CO₂ uptake and carbonation efficiencies were in a similar range, but the reaction times in the semi-dry process were considerably shorter. The proposed method additionally allows for a more simple carbonation setup due to low T and P, and produces an easier to handle product with low water content.     

Strain release in relation to focal depth

Summary The world-wide strain release in relation to focal depth has been calculated for all shocks with magnitude 7 and over for the interval 1918–1952. The strain exhibits a strong maximum in the uppermost 75 km of the earth; it decreases exponentially with depth between 75 and 400 km, with an unimportant minimum corresponding to the asthenosphere low-velocity layer and another minimum at 275 km; after a pronounced minimum between 400 and 475 km it increases again approximately exponentially between 475 and 650 km, after which it drops rapidly to zero. The shape of the strain-depth curve is interpreted in terms of the physical conditions and the intensity of strain accumulation. In particular, the increase between 475 and 650 km is ascribed to a combined effect of temperature and pressure variation with depth with related phase changes and possible changes in composition. The depth curve for the number of shocks is nearly parallel to the strain-depth curve, and the average strain per earthquake shows only an insignificant decrease with depth.

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Zusammenfassung Es wird die Tiefenabhängigkeit der Deformationsauslösung in allen Erdbeben mit Magnitude 7 und darüber, im Zeitraum 1918–1952 untersucht. Die Deformationsauslösung hat ein ausgesprochenes Maximum in den obersten 75 km. Sie nimmt im Tiefenbereich zwischen 75 und 400 km exponential mit der Tiefe ab, wobei sich ein Minimum, das der Schicht mit niedriger Wellengeschwindigkeit entspricht, schwach andeutet, und ein zweites Minimum bei 275 km liegt. Nach einem ausgeprägten Minimum zwischen 400 und 475 km Tiefe, steigt die Deformationsauslösung erneut, etwa exponential, im Tiefenbereich zwischen 475 und 650 km an, und nimmt danach schnell ab. Der Verlauf der Deformationsauslösung in Abhängigkeit von der Tiefe wird an Hand der physikalischen Verhältnisse im Erdkörper, sowie der Intensität der Deformationsaufspeicherung gedeutet. Insbesondere wird der Anstieg zwischen 475 und 650 km einer Änderung der Temperatur und des Druckes mit der Tiefe, bei Phasensprung und möglicher Änderung in der Zusammensetzung des Materials zugeschrieben. Die Tiefenabhängigkeit der Anzahl der Beben und der Deformationsauslösung verlaufen annähernd parallel; die mittlere Deformationsauslösung pro Erdbeben zeigt lediglich eine unbedeutende Abnahme mit der Tiefe.

     

The Triassic of Monte San Giorgio in the World Heritage List of UNESCO: An opportunity for science, the local people and tourism

No abstract.  .     

A method to reconstruct flood scenarios using field interviews and hydrodynamic modelling: application to the 2017 Suleja and Tafa,Nigeria flood

Natural Hazards - The scarcity of model input and calibration data has limited efforts in reconstructing scenarios of past floods in many regions globally. Recently, the number of studies that use...