Effect of climate change on overland flow generation: a case study in central Germany

The impact of global climate change on runoff components, especially on the type of overland flow, is of utmost significance. High‐resolution temporal rainfall plays an important role in determining the hydrological response of quick runoff components. However, hydrological climate change scenario analyses with high temporal resolution are rare. This study investigates the impact of climate change on discharge peak events generated by rainfall, snowmelt, and soil‐frost induced runoff using high‐resolution hydrological modelling. The study area is Schäfertal catchment (1.44 km²) in the lower Harz Mountains in central Germany. The WaSiM‐ETH hydrological model is used to investigate the rainfall response of runoff components under near future (2021–2050) and far‐distant future (2071–2100) climatic conditions. Disaggregated daily climate variables of WETTREG2010 SRES scenario A1B are used on a temporal resolution of 10 min. Hydrological model parameter optimization and uncertainty analysis was conducted using the Differential Evolution Adaptive Metropolis (DREAM_(ZS)) uncertainty tool. The scenario results show that total runoff and interflow will increase by 3.8% and 3.5% in the near future and decrease by 32.85% and 31% in the far‐distant future compared to the baseline scenario. In contrast, overland flow and the number and size of peak runoff will decrease moderately for the near future and drastically for the far‐distant future compared to the baseline scenario. We found the strongest decrease for soil‐frost induced discharge peaks at 79.6% in the near future and at 98.2% in the far‐distant future scenario. It can be concluded that high‐resolution hydrological modelling can provide detailed predictions of future hydrological regimes and discharge peak events of the catchment. Copyright © 2014 John Wiley & Sons, Ltd.     

Néotectonique affectant les dépôts marins tyrrhéniens du littoral sud-est tunisien : implications pour les variations du niveau marin

Pleistocene marine deposits of so-called Tyrrhenian age in southeastern Tunisia include two lithostratigraphic units of Last Interglacial (marine isotopic substage 5e). The lower unit culminates at about +3 m above the sea level; the upper unit with Strombus bubonius culminates at +5 m. Brittle deformations affected the upper unit. The analysis of fault-slip data sets reveals a post-Tyrrhenian N020°E trending compression, consistent with joint patterns. This event induced limited vertical movements, showing that at the northeastern edge of the Saharan Platform, the coastal area of the southern Tunisia remained relatively stable since at least the Last Interglacial.     

Dam break analysis and flood disaster simulation in arid urban environment: the Um Al-Khair dam case study,Jeddah, Saudi Arabia

Natural Hazards - This study used a simulation methodology for dam break analysis and flood simulation in an urbanized arid region, namely Um Al-Khair dam in Jeddah, Saudi Arabia. The analysis was...     

Groundwater origins and mixing pattern in the multilayer aquifer system of the Gafsa-south mining district: a chemical and isotopic approach

Major ion geochemistry and environmental isotopes were used to identify the origins and the mineralisation processes of groundwater flowing within the three aquifer levels of the multilayer system of the Gafsa-south mining district (Southwestern Tunisia). It has been demonstrated that groundwaters are characterised by a Ca–Mg–SO₄ water type. Geochemical pattern is mainly controlled by the dissolution of halite, gypsum and/or anhydrite as well as by the incongruent dissolution of dolomite. δ¹⁸O and δ²H values are much lower than the isotopic signature of regional precipitation and fall close to the meteoric water lines, indicating that groundwaters have not been significantly affected by evaporation or mineral–water reactions. The distribution of stable and radiogenic isotopes (δ¹⁸O, δ²H, δ¹³C and ¹⁴C) within the aquifer levels suggests that the deep confined aquifer receives a significant modern recharge at higher altitudes, while, the shallow unconfined aquifer has been mainly recharged under cooler paleoclimatic condition, likely during Late Pleistocene and Early Holocene humid periods. However, waters from the intermediate confined/unconfined aquifer have composite isotopic signatures, highlighting that they are derived from a mixture of the two first end-members.     

Use of sediment quality indicators for heavy metals contamination and ecological risk assessment in urbanized coastal zones

The urbanized coastal zones are frequently faced to various pollutant discharges mainly in the shoreline. The quantification of the pollution level was mainly based on sea-water analysis. However, in this environment, the sediment characterization, using quality indicators, may constitute an accurate approach. The latter can be particularly appropriate to define heavy metals pollution degree. Chemical analyses of Cd, Cu, Zn, and Fe were undertaken for a total of 45 surface marine sediment samples of Gabes city coast. There is a significant extension of pollution, strongly influenced by the dominant longshore current. The studied sediments were found usually enriched with Cu, Cd, and Zn. These anthropogenic heavy metals have identical behavior and similar distribution. These metals did not show any correlations with Fe chosen as natural tracer. The multi-element indices used permitted to conclude that 70% of sampling sites are highly affected by heavy metal contamination and associated with very high ecological risk. These indices use a simple contamination factor, which, however, would not take account of the sedimentary inputs and the complex sediment behavior. Consequently, modified indices, employing enrichment factor, were used and demonstrated better to assess pollution and ecological risk.     

Palaeoenvironments of the Continental Intercalaire fossil from the Late Cretaceous (Barremian-Albian) in North Africa: a case study of southern Tunisia

Through the Late Cretaceous, the southern shore of the Tethys Ocean migrated north and south over short distances. These vicissitudes are documented in the Continental Intercalaire, a long series of mainly non-marine sediments deposited in which dinosaur or other reptiles tracks and floral fossils are common across southern Tunisia (North Africa). A combined taxonomic, climatological, and palaentological studies provides independent lines of evidence for reconstruction of palaeoenvironments. The Bou Hedma/Boulouha and Sidi Aïch/Douiret Formations from southern Tunisia span the later part of the Late Cretaceous. During the Late Cretaceous the Tunisian territory was an archipelago, thus a particularly suitable area for a more detailed study. We investigated the area’s plant palaeo-biogeography, using fossil wood, with information from both a literature survey and investigation of new samples. The presence of fossils at great depths and distances from the present coastline, without signs of abrasion and far from areas of fluvial discharges does indicate that these remains have not been transported from the continent to the shelf, but have been preserved directly on the area that today correspond to the continental shelf. The climate during the accumulation of Barremian-Albian deposits in this region is inferred to have been warm and humid.     

On the use of mean monthly runoff to predict the flow–duration curve in ungauged catchments

ABSTRACT

We examine the applicability of predicting the daily flow–duration curve (FDC) using mean monthly runoff represented in its stochastic form (MM_FDC) to aid in predictions in ungauged basins, using long-term hydroclimatic data at 73 catchments of humid climate, in the eastern USA. The analysis uses soil hydrological properties, soil moisture storage capacity and the predominant runoff generation mechanism. The results show that MM_FDC did not distinguish the shapes of the upper and lower thirds of the FDC. The upper third is where the precipitation pattern and the antecedent moisture conditions are dominant, while the lower third is where drought-induced low flows and the evapotranspiration effect are prevalent. It is possible to use the MM_FDC to predict the middle third of the FDC (exceedence probabilities between 33% and 66%). The method is constrained by the catchment flow variability (slope of FDC), which changes in accordance with landscape properties and the predominant runoff generation mechanism.     

Solving density driven flow problems with efficient spatial discretizations and higher-order time integration methods

Modelling density driven flow problems requires an excessive computational time and/or heavy equipments due to the non-linear coupling between flow and transport equations. In this work, we develop a robust numerical model with efficient advanced approximations for both spatial and temporal discretizations in order to reduce the excessive computational requirement while maintaining accuracy.     

GIS-based evaluation of groundwater quality and estimation of soil salinization and land degradation risks in an arid Mediterranean site (SW Tunisia)

Arabian Journal of Geosciences - The present work is concerned with the valorization of clay minerals of the Aleg formation (Coniacian-middle Campanian) in the clinker manufacturing. The studied...