Effectiveness of pulse flows in a regulated river for inducing upstream movement of an imperiled stock of Chinook salmon

We assessed the effectiveness of pulse flows in facilitating the upstream migration of an imperiled summer-run Chinook salmon (Oncorhynchus tshawytscha) stock in the Puntledge River, BC, Canada. During July and August, over 3 years, we tracked radio-tagged fish (n = 100) in a reach of the Puntledge River where water is diverted for power generation, resulting in stable low flows that are believed to impede migration. Over the course of  13 pulse flows, we measured migration rate, passage rate at natural barriers that are difficult to pass during low flows, movement away from the turbine outlet pool that creates distracting flows, and locomotor activity. Mean river flow during the peak of the pulses varied from 12.1 to 42.5 m³ s^?1 and was at least 6.1 m³ s^?1 above residual base flows. Typically, the pulse flows lasted 48 h. Migration rate was higher during some pulse flows, but results varied among pulses. Passage at natural barriers was only higher during an abnormal pulse where flows reached twice that of the prescribed flow (i.e., 24+ m³ s^?1). Some fish moved away from the turbine outlet pool during pulse flows. Pulse flows did not affect fish activity levels, as measured by electromyogram telemetry. Although the effect of pulsed flows on the migration of the Puntledge River summer-run Chinook salmon was unclear, no negative impacts, such as hyperactivity or downstream displacement were observed. The use of pulse flows as a management tool still requires further research.     

Impact,Mechanism,Monitoring of Land Subsidence in Coastal Cities(Annual Work of IGCP 663)

正Land subsidence is a worldwide geohazard consisting in the lowering of the ground surface due to natural and human-induced processes occurring in the shallow and deep subsoil.Over the last two decades,land subsidence has caused damages and widespread impacts to a variety of infrastructures in coastal cities (Ma et al.,2011;Liu et al.,2016;Minderhoud et al.,2018).Meanwhile,it is particularly alarming as it reduces the ground     

Eclogite-facies rocks in the Saxonian Erzgebirge,Germany: high pressure metamorphism under contrasting P-T conditions

The metamorphic sequences of the Saxonian Erzgebirge were thoroughly overprinted by a Variscan medium-pressure event under amphibolite facies conditions. However, eclogitic relics documenting an older high-pressure event are widespread. P-T conditions of the eclogite-facies metamorphism systematically decrease, over a distance of 50 km, from about >29 kbar/850°C, in the central part, to 20–24 kbar/650°C, in the westernmost part of the Erzgebirge crystalline complex. A distinct gap in P-T conditions exists between the central and the western Erzgebirge coinciding with the fault zone of the Flöha syncline. Therefore, the eclogitebearing sequences are assumed to represent at least two different nappe units. The lower-grade eclogite assemblages in the western Erzgebirge display a continuous metamorphic zonation with a gradual decrease of peak metamorphic temperatures towards the west. Assemblages formed in the stability field of coesite and thus indicating a regional ultra-high pressure metamorphism, are restricted to the central Erzgebirge, where they are widespread in the eclogites, but also present in metaacidic country rocks. The same high-temperature/high-pressure conditions, testifying to a burial of at least 100 km, were independently recorded for the ultramafic garnet pyroxenites associated with the eclogites of the central Erzgebirge. Mineral relics included in the eclogite phases and mineral assemblages formed by retrograde reactions permit reconstruction of the prograde and retrograde P-T paths in the different parts of the Erzgebirge crystalline complex.     

Centimeter repeatability of the VLBI estimates of European baselines

Summary In the last three years, the European Geodetic Very Long Baseline Interferometry (VLBI) Network has grown to a total of six fixed antennas placed in Germany, Italy, Spain and Sweden, all equipped with the standard geodetic VLBI instrumentation and data recording systems. During this period of time, several experiments have been carried out using this interferometer providing data of very high quality due to the excellent sensitivity and performance of the European stations. The purpose of this paper is to study the consistency of the VLBI geodetic results on the European baselines with respect to the different degrees of freedom in the analysis procedure. In order to complete this study we have made use of both real and simulated data sets, two different software packages (OCCAM 3.0 and CALC 7.4/SOLVE) and a variety of strategies in the data analysis. The results we have obtained show that the repeatability of the VLBI estimates of the baseline lengths in the European network is better than one centimeter, independent of the different analysis methods, and is consistent with the formal error levels expected from the data analysis. This consistency should be enough to produce geophysically significant information in Europe from VLBI data within a relatively short time span.     

Post-fire management effects on sediment (dis)connectivity in Mediterranean forest ecosystems: Channel and catchment response

Forest fires and post-fire practices influence sediment connectivity (SC). In this study, we use the ‘aggregated index of connectivity’ (AIC) to assess SC in five Mediterranean catchments (198–1090 ha) affected by a wildfire in 2012 in south-eastern Spain. Two temporal scenarios were considered, immediately after the fire and before post-fire management, and 2 years after the fire including all practices (hillslope barriers, check-dams, afforestation, salvage logging and skid trails). One LiDAR (light detection and ranging)-derived digital elevation model (DEM, 2 m × 2 m resolution) was generated, per scenario. The five catchment outlets were established as the computation target (AIC_OUT), and structural and functional SC were calculated. Index outputs were normalized to make the results of the non-nested catchments comparable (AIC_N-OUT). The output analysis includes the SC distribution along the catchments and at local scale (929 sub-catchments, 677 in the burned area), the hillslope and channel measures' effect on SC, and a sedimentological analysis using observed area-specific sediment yield (SSY) at 10 new (built after post-fire practices) concrete check-dams located in the catchments (SSY = 1.94 Mg ha⁻¹ yr⁻¹; σ = 1.22). The catchments with more circular shapes and steeper slopes were those with higher AIC_N-OUT. The structural SC maps – removing the rainfall erosivity influence – allowed evaluating the actual role played by the post-fire practices that reduced SC ( $\overline{x}$= − 1.19%; σ = 0.41); while functional SC was linked to the actual change of SC ( $\overline{x}$= + 5.32%; σ = 0.62). Hillslope treatments resulted in significant changes on AIC_N-OUT at sub-catchment scale with certain disconnectivity. A good and positive correlation was found between the SSY and the changes of AIC_N-OUT. However, the coarse DEM resolution explained the lack of effect of the rock check-dams – located on the secondary channels – on AIC_N-OUT. AIC_N-OUT proved to be a useful tool for decision making in post-fire restoration, but an optimal input data is still necessary to refine calculations.     

A Numerical Study of the Impact of Greenhouse Gases on the South Atlantic Ocean Climatology

The National Center for Atmospheric Research Community Climate SystemModel (NCAR CCSM, version 3) numerical coupled model is used tounderstand the climatic impacts on the South Atlantic Ocean due toindustrialization and consequent increase of greenhouse gasemission. Two experiments are analyzed: the first one withtrace/greenhouse gases at pre-industrial levels and a second one wherepresent day levels were adopted. The results show that the annualaveraged sea surface temperature, sea level pressure and barotropictransport intensify and precipitation weakens from one period to thenext. With respect to the seasonal cycle, the sea surface temperaturewarms relative to the pre-industrial period mainly during the winterand spring; while sea level pressure presents higher values in summerand autumn. Barotropic transport has revealed significant differencesbetween the two experiments at middle and high latitudes. Increasedtransport is associated with the intensification of the SubtropicalGyre and the Antarctic Circumpolar Current. Changes in barotropictransport and sea surface temperature leads to an intensification ofthe Polar Front and associated gradients. Examination of theprecipitation field differences showed an increase over the Amazonregion and along the South Atlantic Convergence Zone, during summer.The changes in sea surface temperature, sea-level pressure andbarotropic transport from the pre-industrial period to the present daywere more pronounced at high latitudes. These reach almost 1 °Cand 11Sv between 45-60° S, respectively. Majordifferences in precipitation are confined to the tropics.     

Influence of Decarbonisation and Phosphate Dosage on Copper Corrosion in Drinking Water Systems

The effect of softening/decarbonisation and dosage of orthophosphate on copper corrosion was studied in pipe rigs according to the German standard DIN 50931, part 1. A literature study with regard to the effects of phosphate dosing on copper corrosion has shown that on the one hand and in most of the cases a dosage of phosphate led to lower copper concentrations. On the other hand phosphate aggravated the copper corrosion in some cases. The mechanisms are not yet clear and the influence of phosphate on the corrosion of copper remains a question to be answered. Using standardised on‐site corrosion tests (DIN 50931‐1) with virgin copper pipes softening/decarbonisation has decreased the copper concentration. Two effects of phosphate on copper corrosion were noticed: Phosphate dosing decreased the copper oxidation and resulted in lower copper concentration in water. Likewise phosphate hindered the precipitation of cupric ions, which prolonged the existence of copper in water and resulted in a higher copper concentration. As a consequence, dosing phosphate can decrease or increase the copper corrosion, this depends on which effect is dominating.     

Gravimetric determination of an intrusive complex under the Island of Faial (Azores): some methodological improvements

We present some improvements of a gravity inversion method to determine the geometry of the anomalous bodies for priori density contrasts. The 3-D method is based on an exploratory process applied, not for the global model, but for the steps of a growth approach. The (positive and/or negative) anomalous structure is described by successive aggregation of cells, while its corresponding gravity field remains nearly proportional to the observed one. Moreover, a simple (e.g. linear) regional trend can be simultaneously adjusted. The corresponding program is applied to new gravity data on the volcanic island of Faial (Azores archipelago). The inversion approach shows a subsurface anomalous structure for the island, the main feature being an elongated high-density body. The body is interpreted as a compact sheeted dyke swarm, emplaced along Faial-Pico Fracture Zone, a leaky transform structure that forms the current boundary between Eurasian and African plates in the Azores area. The new results in this paper are (1) a Bouguer gravity anomaly map, (2) several improvements in the inversion process (robust process, optimal balance fitness/model magnitude), (3) a new gravimetric method for estimating the mean terrain density, (4) a 3-D model for subsurface mass anomalies in Faial and (5) some interpretative conclusions about a main intrusive complex detected under the island as a wall-like structure extending from a depth of 0.5 to 6 km b.s.l., with a N100°E trend and corresponding to an early fissural volcanic episode controlled by the regional tectonics.     

人工回灌对地下水年龄分布规律的影响

地下水可更新能力是评价地下水开发可持续性的关键指标,可更新能力可以用地下水年龄来定量表达。在人类活动影响下,地下水的实际更新状况已与自然条件下截然不同。基于台兰河流域地下水库建设和人工回灌工作现状,通过物理试验和数值模拟相结合的方法分别研究了入渗池位置,回灌强度和包气带厚度对地下水年龄分布规律的影响。结果表明:人工回灌使地下水年龄整体变年轻;入渗池位置和回灌强度的改变对地下水年龄分布的影响显著;包气带厚度的增大使回灌水滞留时间延长,导致地下水年龄增大,该研究可为合理评价区域地下水可更新能力提供技术指导。