Incipient motion and drift of benthic invertebrates in boundary shear layers

River engineeringRiver habitat management and restoratio

guidelines for end-users ; 32 Tabellen

PREFACE: The problem of prevention with regard to floodplains is related to two extremes: Prevention of floods and prevention of droughts, both urgent socioeconomic issues during the last years. „Retard the flow of water in the stream corridor“ is the message to cope with both kind of problems. An amphibian landscape will help to maintain water supply during periods of droughts and by its retention area to reduce peaks of high floods. Flood retention areas will function sustainably only if there is an intact ecological system and equilibrium between erosion and accumulation of sediments which in turn both depend from the evolution of the hydraulic conditions and from the succession of the riparian forest. The RipFor — project laid emphasis on the hydraulic processes and their erosion / accumulation effects in retention areas with the aim to get insight into the interaction between riparian vegetation, sediment transport, hydraulics and ecology. Interdisciplinary and intereurOpean work was carried out in the field, the laboratory and by modelling. Results of the RipFor — project as presented in the scientific report and the attached „guidelines for End-Users “ in this way are a contribution to the international discussion on river restoration and to the implementation of the European Water Framework Directives. The scientific report was compiled by Ingo Schnauder and Jens Bölscher (Karlsruhe and Berlin) from contributions of all partners, whereas the bulk of work on the „Guidelines“ was done by Ingo Schnauder (Karlsruhe), Jens Bölscher (Berlin) and Harald Meixner (Vienna), who also cared for the layout. Reporting of the Romanian NAS partner was directed by Virgil Iordache. Assistance of subcontractors and endusers is highly appreciated, especially by Othmar Huppmann (Regierungspräsidium Freiburg / former Gewässerdirektion Oberrhein). Funding within „Quality of Live and Management of Living Resources“ in the RP5 framework of the European Union was essential for this project and is highly acknowledged. Prof. Dr. Peter-Jürgen ErgenzingerresearchDFG, SUB Göttingen, FU Berli

Development of a catchment-wide nutrient model

Diffuse-source nutrient pollution remains a major problem within sustainable catchment management. The aim of this study is to provide a decision-support tool that can predict the impact of land-use changes on water quality (WQ) in receiving waters. A linked modelling approach was used to integrate land-use changes with a WQ model and a 2D numerical hydrodynamic model. The linked model was adapted to conditions in estuarine and coastal waters and applied to the catchments of Carmarthen Bay in West Wales, UK. A new set of biochemical reaction rates for nutrients in estuarine waters was found and presented. This approach took into account the assessment of nutrient production rates in the catchment for dry and wet weather conditions, as well as the reactions of constituents passing from the catchment into the coastal basin. The predominant types of land use in the catchment are arable land, improved grassland, rough grazing and woodland. Nutrient loads from these areas were estimated using Geographical Information System (GIS) data and export coefficients, which characterise the amount of nutrient losses. Furthermore, economical and ecological effects of land-use changes were integrated using an input–output analysis approach. A range of scenario simulations involving different river discharges and reduced nutrient input rates resulting from appropriate measures for land-use changes showed the nutrient pathways and concentration distributions over time throughout the bay. The outcome from these scenario simulations can be used to indicate catchmentwide distribution of diffuse pollution sources and to locate areas that are characterised by high nutrient concentrations and are prone to the occurrence of mass algal growth. Author(s): B. Bockelmann-Evans | I. Schnauder | E. Fenrich | R. Falcone

Injection Site Matters: A Comparative Analysis of Transpulmonary Thermodilution via Simultaneous Femoral and Jugular Indicator Injections under Veno-Venous Extracorporeal Membrane Oxygenation Therapy

Background: The use of veno-venous extracorporeal membrane oxygenation (vv-ECMO) in acute lung failure has witnessed a notable increase. The PiCCO system is frequently used for advanced hemodynamic monitoring in this cohort. Our study aimed to investigate whether the choice of indicator injection site (jugular vs. femoral) in patients undergoing vv-ECMO therapy affects transpulmonary thermodilution (TPTD) measurements using the PiCCO® device (Pulsion Medical Systems SE, Munich, Germany). Methods: In a retrospective single-center analysis, we compared thermodilution-derived hemodynamic parameters after simultaneous jugular and femoral injections in 28 measurements obtained in two patients with respiratory failure who were undergoing vv-ECMO therapy. Results: Elevated values of the extravascular lung water index (EVLWI), intrathoracic blood volume index (ITBVI) and global end-diastolic volume index (GEDVI) were observed following femoral indicator injection compared to jugular indicator injection (EVLWI: 29.3 ± 10.9 mL/kg vs. 18.3 ± 6.71 mL/kg, p = 0.0003; ITBVI: 2163 ± 631 mL/m2 vs. 806 ± 125 mL/m2, p 2 vs. 687 ± 141 mL/m2, p Conclusions: In a PiCCO®-derived hemodynamic assessment of patients on vv-ECMO, the femoral indicator injection, as opposed to the jugular injection, resulted in an overestimation of all index parameters. This discrepancy can be attributed to mean transit time (MTt) and downslope time-dependent (DSt) variations in GEDVI and cardiac function index and is correlated with ECBF

Dynamics of shallow lateral shear layers: Experimental study in a river with a sandy bed

Shallow lateral shear layers forming between flows with different velocities, though essential for mixing processes in natural streams, have been examined only in laboratory settings using smooth, fixed?bed channels. This paper reports the results of an experimental study of a shear layer in a straight reach of a natural river where the layer, in contrast to the two?dimensional structure observed in the laboratory, is highly three?dimensional. The study included pronounced transverse pressure gradients, which influenced shear layer structure compared to flume experiments. It also introduces an analysis that complements conventional theory on mixing layers. The lateral velocity gradient between the flows downstream from a splitter plate placed in the river, the principal controlling factor, was adjusted for three experimental runs to determine the influence of different gradients on shear?layer dynamics. In each run, detailed three?dimensional measurements of mean and turbulent characteristics were obtained at five cross sections downstream from the splitter plate. Although experimental results agreed with conventional mixing?layer theories with respect to turbulence, the dynamics of the shear layers were dominated by the mean lateral fluxes of momentum. After re?examining the governing equations, we developed a parabolic equation describing the shear layer evolution and several scaling relations for essential terms of the energy budget: mean and turbulent lateral fluxes of momentum, turbulent kinetic energy, and dissipation rates. The study also provides insight into the spectral dynamics of turbulence in the shear layer and clarifies previous observations reported for confluences in natural streams.Hydraulic EngineeringCivil Engineering and Geoscience