River Western Research Articles

Perceptions et enjeux de gestion des rivières de l’Ouest par les gestionnaires de l’eau - entre influence de parcours et pragmatisme de terrain

En France, les rivières sont l’objet de nombreuses interventions pour restaurer les continuités écologiques et/ou diversifier les écoulements, notamment guidées par la Directive européenne Cadre sur l’Eau (2000) et la Loi sur l’Eau et les Milieux Aquatiques (2006). Si un champ de recherche sur les rivières de l’Ouest et leurs évolutions est actif depuis une quinzaine d’années, l’analyse de la gestion et surtout des gestionnaires semble faire défaut. Pourtant, ces derniers peuvent influencer de manière non négligeable la gestion de ces espaces et donc leurs dynamiques. Dans le cadre de cette recherche, nous nous sommes intéressés aux métiers de gestionnaires de l’eau et aux formations initiales permettant de les exercer. A l’aide d’entretiens par questionnaires, d’entretiens semi-directifs, d’observations de terrain, d’analyses des contenus de formations et de fiches de postes de gestionnaires de l’eau, nous apportons un éclairage sur la diversité des contextes de gestion, des formations proposées pour devenir gestionnaires de l’eau et démontrons l’influence des formations initiales dans la perception de la gestion des rivières. Enfin, le lien usagers-gestionnaires s’est révélé particulièrement important aux yeux des deux parties prenantes afin d’atteindre une gestion satisfaisante, alors que le temps disponible pour le terrain et les usagers chez les agents semble en forte diminution. Cela n’est pas sans interroger sur les moyens et l’adéquation de la gestion actuelle et future pour répondre aux enjeux environnementaux et sociétaux émergeants.

Landscapes of the Lake Eyre Basin: the catchment-scale context that creates fluvial diversity

ABSTRACT Lake Eyre Basin (LEB) rivers are important but under-researched. This study integrates published and new information into a systematic geomorphological overview, subdividing the LEB into nine landscape zones: basin-margin Uplands with relatively high-energy rivers; Rocky Fringe, piedmont with short rivers and floodouts; Western Rivers, notable for neotectonism and stream capture; low-relief Northern Plains drainages and floodouts; Central Plains dunefield; Channel Country-Vertic Downs, cracking-clay interfluves and valley macrochannels; Channel Country-Stony Domes, rocky or sandy interfluves and complex macrochannels; Lakes & Dunes maintained by saline groundwater; and playas in the Mega-lakes. Zone boundary GIS datasets are available. LEB rivers are shown to be diverse and distinctive, indicating a need for locally relevant knowledge in management and monitoring. Fluvial landform suites include sand-bed rivers, macrochannels hosting coexisting anabranching and anastomosing systems in vertic floodplains, floodouts, low-angle alluvial fans, and three types of waterhole. Channels may be discontinuous or not present; floodplains can dominate flow transmission. Contributing hillslopes are heterogenous in their capacity to generate runoff, while drainage networks may have low to high degrees of integration. Management implications include the importance of in-river terrestrial ecosystems and “patchy” drainage networks, and the inapplicability of some morphometric practices.

A comprehensive assessment of anthropogenic impacts, contamination, and ecological risks of toxic elements in sediments of urban rivers: A case study in Qingdao, East China

Urban river sediments usually serve as a sink for potentially toxic elements (PTEs) during the process of urbanization. A systematic evaluation of human influence, contamination, and risk assessment of PTEs in urban river sediments is essential for sustaining river health. In this study, 24 sediment samples were collected from 5 rivers in Qingdao, a coastal urbanized city in East China. Zinc had the highest concentration (141 ± 134 mg/kg), followed by Cr, Cu, Pb, Ni, Co, As, and Cd. Generally, the PTE concentrations were higher in eastern rivers than those in western rivers affected by intensive industrialization and urbanization. The principal component analysis identified three principal components: natural origins (As, Co, Cr, and Ni), urban activities (Cd, Cu, Pb, and Zn), and atmospheric deposition (Pb), respectively. The excessive concentrations of Cd and Pb were frequently appeared in the sampling sites, with the anthropogenic contribution rates of 8.4%–77% and 6.6%–87%, respectively. Additionally, the river sediments experienced moderate contamination of As, Cd, Cu, Pb, and Zn. Among the PTEs, Cd had moderate ecological risk and others had low risk. The results of Monte Carlo simulation were generally in accordance with the detected contamination and risk levels, except for several elements (Cu and Zn) with huge spatial heterogeneity. According to the Monte Carlo simulation, the river sediments could undergo extremely high contamination and high ecological risk of the PTEs in the worst situation. Thus, it becomes essential that PTEs in the urban rivers should not be overlooked before their discharge into the sea.

Hydro-Hegemony Framework: A study of the India Pakistan trans-boundary water competition and cooperation

After the independence of Pakistan and India in 1947, both the newly established states submerged in many tensions leading to competition in many areas. One such area is the hydro competition between the two closely bordering states. Within this context, India and Pakistan kicked by perianal security dilemma at all levels. India is diverting water from western rivers, which is not permissible for India in Indus Water Treaty (IWT). The Purpose of this study is to find out the reason/s that why India is behaving in this way? This is an applied research within the context of Hydro-Hegemony Framework (HHF) theory. According to the theory, India is behaving hydro-hegemonically because of the three reasons stated by Hydro-Hegemony Framework; firstly, because of Indian advantageous upper-riparian geographical position; secondly, because of Indian superior technical potential and ability to construct a lot of dams; thirdly power asymmetry exists between India and Pakistan. India because of these three main reasons is desirous to get “Consolidated Water Control” over three western rivers assigned to Pakistan by Indus Water Treaty. Indian endeavours to get water dominance would complicate its relations with Pakistan. Indian hydro-hegemony would impact Pakistan’s economy, hydro-power generations projects, agriculture sectors and domestic hydro-usage

Measurement, quantification, and potential risk of microplastics in the mainstream of the Pearl River (Xijiang River) and its estuary, Southern China.

The goals of this study were to investigate the distribution profiles, sources, and inventory of microplastics in the surface water of the mainstream of the Pearl River (Xijiang River) and its estuary, China, and to assess the potential ecological risks of the microplastics in this subtropical riverine habitat. The results showed that the microplastic abundances of the Humen (HUM, 16.33 ± 0.88 items/L), Zhaoqing (ZQ, 15.33 ± 0.67 items/L), and Hutiaomen (HTM, 14.67 ± 1.33 items/L) sites were significantly higher than those of the other sampling sites, indicating that the microplastics in Xijiang River and its estuary exhibited an unbalanced spatial distribution. The most common microplastic color was transparent and the major shape of the microplastics was fragments. Microplastics with a size of 0.01-0.1 mm were dominant throughout the 16 sampling sites. Polyolefin elastomer (POE, 33.33%), polyethylene terephthalate (PET, 23.81%), and polyurethane acrylate (PUA, 14.29%) were the dominant microplastic polymers. The microplastic abundance co-varied with most of the selected socio-economic indicators, including the population density, urban land area, gross domestic product (GDP), freshwater aquatic products, and freshwater cultivated area, but without significant differences, indicating that there are additional factors affecting the microplastic abundance. The potential risk (i.e., the potential ecological risk, RI; polymer risk index, H; and pollution load index, PLI) posed by the microplastics was higher in HUM, followed by ZQ and HTM, and it was lower for the other sites, suggesting that the main outlets and the biggest city on the Xijiang River contributed more to the high risks of microplastic pollution. Consistent with microplastic abundance distribution profiles, the average potential risk index values of the western river outlets were higher than those of the eastern river outlets and the Xijiang River, implying that the western river outlets had non-negligible potential ecological risks. Our findings deepen the understanding of the risks posed by microplastics and further contribute to microplastic risk management of riverine ecosystems.

Flow modification associated with reduced genetic health of a river‐breeding frog, Rana boylii

AbstractRiver regulation or flow modification—the hydrological alteration of flow by dams and diversions—has been implicated as a cause of fundamental change to downstream aquatic ecosystems. Flow modification changes the patterns and functionality of the natural flow regime and has the potential to restrict population connectivity and gene flow in river‐dependent organisms. Since population connectivity and the maintenance of genetic diversity are fundamental drivers of long‐term persistence, understanding the extent flow modification impacts these critical attributes of genetic health is an important goal for long‐term conservation. Foothill yellow‐legged frogs (Rana boylii) were historically abundant throughout many western rivers but have declined since the onset of flow regulation. However, the extent to which R. boylii populations in rivers with altered flow regimes are maintaining connectivity and genetic diversity is unknown. Here, we use population genomics to investigate the impacts of flow alteration on R. boylii to explore their potential for long‐term persistence under continued flow modification. We found R. boylii in rivers with flow modification showed striking patterns of isolation and trajectories of genetic diversity loss relative to unregulated rivers. For example, flow modification explained the greatest amount of variance in population genetic differentiation compared with other covariates including geographic distance. Importantly, patterns of connectivity and genetic diversity loss were observed regardless of flow alteration level but were most prominent in locations with the greatest flow modification intensity. Although our results do not bode well for long‐term persistence of R. boylii populations under current flow regulation regimes, they do highlight the power of genetic monitoring for assessing population health in aquatic organisms.

Evaluation of the subseasonal forecast skill of floods associated with atmospheric rivers in coastal Western U.S. watersheds

AbstractAtmospheric rivers (ARs) are responsible for up to 90% of major flood events along the U.S. West Coast. The timescale of subseasonal forecasting (two weeks to one month) is a critical lead time for proactive mitigation of flood disasters. The NOAA/Climate Testbed Subseasonal Experiment (SubX) is a research-to-operations project with almost immediate availability of forecasts. It has produced a reforecast database that facilitates evaluation of flood forecasts at these subseasonal lead times. Here, we examine the SubX driven forecast skill of AR-related flooding out to 4-week lead using the Distributed Hydrology Soil Vegetation Model (DHSVM), with particular attention to the role of antecedent soil moisture (ASM), which modulates the relationship between meteorological and hydrological forecast skill. We study three watersheds along a transect of the U.S. West Coast: the Chehalis River basin in Washington, the Russian River basin in Northern California, and the Santa Margarita River basin in Southern California. We find that the SubX driven flood forecast skill drops quickly after week 1, during which there is relatively high deterministic forecast skill. We find some probabilistic forecast skill relative to climatology as well as ensemble streamflow prediction (ESP) in week 2, but minimal skill in weeks 3-4, especially for annual maximum floods, notwithstanding some probabilistic skill for smaller floods in week 3. Using ESP and reverse-ESP experiments to consider the relative influence of ASM and SubX reforecast skill, we find that ASM dominates probabilistic forecast skill only for small flood events at week 1, while SubX reforecast skill dominates for large flood events at all lead times.

The Hydropolitics of the Indus Waters Treaty: A Critical Perspective

This paper discusses the hydro politics of the Indus Waters Treaty from a critical perspective. Many analysts and commentators from both India and Pakistan expressed displeasure with the treaty on the grounds of allotting more waters to the contending party. The Indian side is displeased with 'restricted' rights on western rights, whereas the Pakistani side laments the Indian rights on the western rivers as detrimental to its water security. Neutral experts consider the Indus Waters Treaty as an instance of successful water dispute resolution. However, the treaty's failure to account for future implications of the climate change for water supply and surging population for water demand as well as the absence of the other co-riparians of China and Afghanistan from the treaty and its failure to hardwire enough safeguards to ensure Kashmiri's needs are met from the waters add to the stresses and strains in the Indus Waters Treaty.

Range Expansion of the Cleptoparasitic Orchid Bee Aglae caerulea in the Pantanal of Mato Grosso, Brazil

In the present study, a new occurrence of Aglae caerulea Lepeletier & Audinet-Serville is reported within a few km of the seasonal flooded plain limits of the Pantanal in the Paraguay basin, reinforcing the idea that this species coexists with its hostess Eulaema nigrita, one of the most common species catalogued in several habitats surveyed in the biome. After 18 months of sampling and no A. caerulea male attracted to the baits, methyl cinnamate was added to the set of fragrances available in the field. During four weeks in May and one week in June 2018, a total of 11 males of A. caerulea were attracted to the new bait in the gallery forest of São Vicente Range. With this most recent record, we expand the ranges of occurrence to the north-eastern border of the Pantanal of Barão de Melgaço, in Mato Grosso, Brazil. Future expeditions in the Pantanal of Mato Grosso and Mato Grosso do Sul should record this cleptoparasitic species from southern to western Paraguay river basin, to reduce the biogeographical gaps in this peculiar tribe of corbiculate bees. The cleptoparasitic species A. caerulea may be recorded when adequate field studies and collections are made from the seasonal floodplain habitats to karstic habitats (dry forests) along the Pantanal border.

Chemical and Genotypic Variations in Aniba rosiodora from the Brazilian Amazon Forest.

Aniba rosiodora has been exploited since the end of the nineteenth century for its essential oil, a valuable ingredient in the perfumery industry. This species occurs mainly in Northern South America, and the morphological similarity among different Aniba species often leads to misidentification, which impacts the consistency of products obtained from these plants. Hence, we compared the profiles of volatile organic compounds (essential oils) and non-volatile organic compounds (methanolic extracts) of two populations of A. rosiodora from the RESEX and FLONA conservation units, which are separated by the Tapajós River in Western Pará State. The phytochemical profile indicated a substantial difference between the two populations: samples from RESEX present α-phellandrene (22.8%) and linalool (39.6%) in their essential oil composition, while samples from FLONA contain mainly linalool (83.7%). The comparison between phytochemical profiles and phylogenetic data indicates a clear difference, implying genetic distinction between these populations.

Indirect emissions of nitrous oxide in a cropland watershed with contrasting hydrology in central France

Nitrous oxide (N2O) is an important greenhouse gas. Its atmospheric concentration have increased with the industrialisation and the use of N fertilizer. The contribution of freshwater systems to N2O emissions is still very uncertain, while regional transfer of nitrogen depends on soil and hydrology. Riverine and spring N2O dissolved in water was therefore measured over two years in the 3453 km2 Haut-Loir watershed (France). This temperate cropland watershed is characterized by two different hydrological systems east and west of the Loir River. The eastern rivers, fed by the emergence of the deep Beauce aquifer, exhibited significantly higher dissolved N2O concentrations (Beauce region, mean: 2.93 μg-N L−1) than the western rivers (Perche region, mean: 0.87 μg-N L−1), which were largely influenced by runoff during winter flooding. The eastern rivers had large nitrate concentrations all over the year; in the Perche, nitrate underwent a seasonal cycle with large loads during winter floods, but there were no consistent seasonal patterns in N2O. The ratios of N2O in excess of equilibrium on nitrate, often used as a proxy of emission factor (EF), were much smaller than the default IPCC values, both for rivers (0.014% versus 0.25% for IPCC EF5r) and the Loir spring (0.085% versus 0.6% for the IPCC EF5g for groundwater and springs). EF5r were significantly different between the two parts of the watershed only in winter, because of the seasonal variability of NO3−. Moreover dissolved N2O is controlled not only by NO3−, as it is considered in the calculation of the EF5, but also by water pH and dissolved organic carbon. A good prediction of dissolved N2O was obtained using these physicochemical variables and hydrological regions. Thus, these results suggest that the spatial variability of riverine N2O depends on local hydrology, while further research is needed to understand the seasonal variability.

Assessing Evolutionary Significant Units (ESU) of the Endangered Freshwater Pearl Mussel (Margaritifera margaritifera) in Southeast Norway on the Basis of Genetic Analysis.

A total of 312 specimens of freshwater pearl mussel (Margaritifera margaritifera) were sampled from 11 populations, located in four different river systems in Southeast Norway, and analyzed for 11 simple sequence repeat (SSR) (microsatellite) markers. All study populations have landlocked brown trout (Salmo trutta) as the only possible host. Several populations had experienced recruitment failure, probably due to low pH (about 6.0) and calcium concentration. STRUCTURE clustering analysis revealed two genetic clusters, of which one cluster occurred mainly in the western river systems, and totally dominated in one population (Fallselva (A-FAL)) that had higher genetic diversity than the others. Cluster 2 completely dominated in the populations of the eastern river systems, and all of them had low genetic diversity. Bottleneck events were indicated in all populations and the inbreeding coefficient FIS was significant in all populations, except for the southernmost population (Sørkedalselva (B-SØR)), which was the only population with genotypes in Hardy–Weinberg equilibrium. FIS were especially high in the populations of the eastern river systems, and maximum shell length was negatively correlated to FIS. If artificially breeding and stocking should become necessary for future preservation, it should be based on single populations; alternatively, the eastern populations should be based on cross-breeding of populations within the cluster to increase their genetic diversity.

Changes in Snow Cover Dynamics over the Indus Basin: Evidences from 2008 to 2018 MODIS NDSI Trends Analysis

The frozen water reserves on the Earth are not only very dynamic in their nature, but also have significant effects on hydrological response of complex and dynamic river basins. The Indus basin is one of the most complex river basins in the world and receives most of its share from the Asian Water Tower (Himalayas). In such a huge river basin with high-altitude mountains, the regular quantification of snow cover is a great challenge to researchers for the management of downstream ecosystems. In this study, Moderate Resolution Imaging Spectroradiometer (MODIS) daily (MOD09GA) and 8-day (MOD09A1) products were used for the spatiotemporal quantification of snow cover over the Indus basin and the western rivers’ catchments from 2008 to 2018. The high-resolution Landsat Enhanced Thematic Mapper Plus (ETM+) was used as a standard product with a minimum Normalized Difference Snow Index (NDSI) threshold (0.4) to delineate the snow cover for 120 scenes over the Indus basin on different days. All types of errors of commission/omission were masked out using water, sand, cloud, and forest masks at different spatiotemporal resolutions. The snow cover comparison of MODIS products with Landsat ETM+, in situ snow data and Google Earth imagery indicated that the minimum NDSI threshold of 0.34 fits well compared to the globally accepted threshold of 0.4 due to the coarser resolution of MODIS products. The intercomparison of the time series snow cover area of MODIS products indicated R2 values of 0.96, 0.95, 0.97, 0.96 and 0.98, for the Chenab, Jhelum, Indus and eastern rivers’ catchments and Indus basin, respectively. A linear least squares regression analysis of the snow cover area of the Indus basin indicated a declining trend of about 3358 and 2459 km2 per year for MOD09A1 and MOD09GA products, respectively. The results also revealed a decrease in snow cover area over all the parts of the Indus basin and its sub-catchments. Our results suggest that MODIS time series NDSI analysis is a useful technique to estimate snow cover over the mountainous areas of complex river basins.

Characterisation of hydrological droughts in centralnorth Argentina and their atmospheric and oceanic drivers

Low streamflows caused by natural and anthropogenic forcings affect ecosystems and societies, especially on large timescales. We analysed the main basins of central-north Argentina (CNA) using centennial streamflow data. This study is focussed on describing spatial and temporal variability of hydrological drought events, and evaluating the atmospheric and oceanic drivers under hydrological drought conditions. The Standardized Streamflow Index in the period 1919-2014 was applied, sectored by 4 major basins. The western Argentinian rivers (Colorado Basin, CB) have shown increasing drought events since the 1940 decade, while in the east, a sharp decrease occurred from 1970 onwards. Extreme drought events occurred over CB and La Plata Basin (LPB) during the periods 1966-1972 and 2010-2014. Atmospheric and oceanic patterns under hydrological drought conditions show anticyclonic anomalies over the South Pacific Ocean (SPO), cyclonic sub-polar anomalies and La Niña-like conditions with warm sea surface temperature anomalies (SSTAs) in SPO for the western basins. Over LPB, a strong cold SSTA in the tropical south-western Atlantic Ocean is positioned in phase with the cyclonic anomalies. At mid-latitudes, a warm SSTA and anticyclonic anomalies are detected. Water vapour transport composites show southerly winds and drier conditions for northern and eastern Argentina, and weakening of westerly winds with drier atmosphere for western rivers. These results deepen our knowledge of natural forcings related to hydrological drought events in CNA and in the predictability of such complex natural hazards.

Water Security Assessment for the Contiguous United States Using Water Footprint Concepts

AbstractWater security is tightly connected with the food security, ecological health, and economic prosperity of a region. In this study, a comprehensive water security assessment based on water footprint concepts from 1995 to 2015 was performed for the counties located in the Contiguous States of the Unites States. The availability of blue water (e.g., surface water) is comparatively less in the western river basins, and most of the rainfed agricultural lands in the eastern United States were characterized by the lower levels of green water (e.g., root zone soil moisture) storage. This integrated assessment of the water security indicators can directly map the critical regions and reveal the dependence between human water consumption, crop water requirements and environmental flow. This analysis can be further extended to incorporate climate change and extreme drought events to inform specific locations (e.g., counties and watersheds) at which problems of water conflict are more likely to occur.

Predictive skill for atmospheric rivers in the western Iberian Peninsula

Abstract. A large fraction of extreme precipitation and flood events across western Europe are triggered by atmospheric rivers (ARs). The association between ARs and extreme precipitation days over the Iberian Peninsula has been well documented for western river basins. Since ARs are often associated with high impact weather, it is important to study their medium-range predictability. Here we perform such an assessment using the ECMWF ensemble forecasts up to 15 d for events where ARs made landfall in the western Iberian Peninsula during the winters spanning between 2012–2013 and 2015–2016. Vertically integrated horizontal water vapor transport (IVT) and precipitation from the 51 ensemble members of the ECMWF Integrated Forecasting System (IFS) ensemble (ENS) were processed over a domain including western Europe and the contiguous North Atlantic Ocean. Metrics concerning AR location, intensity, and orientation were computed, in order to compare the predictive skill (for different prediction lead times) of IVT and precipitation. We considered several regional boxes over western Iberia, where the presence of ARs is detected in analysis/forecasts, enabling the construction of contingency tables and probabilistic evaluation for further objective verification of forecast accuracy. Our results indicate that the ensemble forecasts have skill in detecting upcoming AR events, which can be particularly useful to better predict potential hydrometeorological extremes. We also characterized how the ENS dispersion and confidence curves change with increasing forecast lead times for each sub-domain. The probabilistic evaluation, using receiver operating characteristic (ROC) analysis, shows that for short lead times precipitation forecasts are more accurate than IVT forecasts, while for longer lead times this reverses (∼10 d). Furthermore, we show that this reversal occurs for shorter lead times in areas where the AR contribution is more relevant for winter precipitation totals (e.g., northwestern Iberia).

Geoarchaeological evidence of Ostia\u2019s river harbour operating until the fourth century AD

Ancient Ostia at the mouth of the River Tiber into the Tyrrhenian Sea was largely significant for the economic supply of Rome. Ostia itself experienced an extraordinary period of prosperity in the second century AD. Starting in AD 42, a first new harbour at Portus was built by Emperor Claudius close to Ostia. It reached its full functionality under Emperor Trajan in the early second century AD, only. At Ostia itself, previous archaeological and geoarchaeological studies have brought to light a lagoon-type harbour at the western fringe of the city operating between the fourth and the second century BC in an artificially excavated harbour basin. From the second century BC onwards, a considerably smaller and shallower part of this western harbour basin was still in function as a fluvial harbour. So far, it was unclear whether Ostia’s western harbour was still in use when the harbour at Portus was set into function in the first to second century AD, or if the latter partially replaced Ostia’s harbour infrastructure. According to archaeological evidence, Ostia’s navalia-temple-complex, the main building at the eastern fringe of the western river harbour basin, was built in the second quarter of the first century AD. Was this prestigious harbour building erected although the associated harbour seemed to have been already given up before? We conducted detailed geoarchaeological investigations at the immediate western front of the navalia-temple complex. Results were compared with archaeological data obtained from excavations carried out in 2000/2001. A multi-proxy approach was used to reconstruct the history and evolution of the harbour. It was possible to identify subsurface structures and evaluate the local stratigraphy. Vibracoring brought to light a more than 1 m thick section of an opus reticulatum wall with parts of the original opus latericium on top. Such walls originally separated vaulted shipshed chambers of the navalia-temple complex at Ostia, which in turn formed the substructure of a temple complex located above it. Another core revealed the sedimentary infill of a former chamber of the building. Based on radiocarbon dating, the navalia was in use between the first and the fourth centuries AD with a water depth of maximum ca. 1.2 m at the immediate western front. This is in agreement with the date of construction of the navalia-temple complex in the second quarter of the first century AD. The relative sea level at that time was around 0.64 m below the present sea level. The harbour and the navalia were obviously accessible only for flat-keeled lighters and cargo boats. Larger cargo ships were either unloaded along the riverbank to the north of ancient Ostia (Hadler et al. 2019) or moored offshore, their freight being reloaded to smaller lighters. Chronostratigraphic data further show that the navalia-temple complex was in use until the second half of the fourth century AD. It was not before AD 355–363 or shortly afterwards, that the harbour site was abandoned. Ostia’s western river harbour was neither abandoned nor completely silted up before the harbour at Portus was established as previously assumed by other authors. Actually, the western front of the navalia-temple complex was hit by an extreme wave event, leaving a sand layer approx. 0.5 m thick, at or shortly after AD 355–363 which led to the final abandonment of Ostia’s western river harbour. This event is interpreted as a tsunami that may have hit the wider coastal region.

Pathways and mixing of the north western river waters in the Black Sea

Given the increasing role of river-borne anthropogenically-derived substances on the water quality of impacted marine ecosystems, it is important to study the pathways of the river waters in the Black Sea. We perform tracer simulations for the river-borne substance, aiming to track its transport and accumulation in the basin and to identify possible long term trends. Our results suggest a decrease in Danube plume transport southward along the coastline and increasing transport to the north and north-eastern parts of the North Western Shelf (NWS) and then to the southwest. Over the 1960–2017 period, the Black Sea circulation showed an amplification and consolidation of the Rim Current, most likely in response to climatic changes. Recent changes in the circulation patterns seem to be a key factor for the modification of the river plume pathways. The concentration of the river-borne substance reaches an annual maximum in September, when pulses with larger tracer concentrations can be found in the inner basin. The accumulation of river-borne substance on the north and south shelf has increased in recent decades.

Habitat and community structure modulate fish interactions in a neotropical clearwater river

ABSTRACT Species interactions can modulate the diversity and enhance the stability of biological communities in aquatic ecosystems. Despite previous efforts to describe fish interactions in tropical rivers, the role of habitat characteristics, community structure, and trophic traits over these interactions is still poorly understood. To investigate among-habitat variation in substratum feeding pressure and agonistic interactions between fishes, we used remote underwater videos in three habitats of a clearwater river in the Central Western, Brazil. We also performed visual surveys to estimate the abundance and biomass of fishes and proposed a trophic classification to understand how these variables can affect fish interactions. Community structure was the main factor affecting the variation in the interactions among the habitats. Biomass was the main variable determining which habitat a fish will feed on, while species abundance determined with how many other species it will interact in the agonistic interaction networks for each habitat. Specific habitats are not only occupied, but also used in distinct ways by the fish community. Overall, our results demonstrate the importance of the heterogeneity of habitats in tropical rivers for the interactions performed by the fishes and how the intensity of these interactions is affected by community structure.

The Effect of Using Cokriging against Ordinary Kriging When Estimating Phosphate Deposits at Elsebaiya Area, Egypt

Application of geostatistical techniques when evaluating mineral deposits could reflect some geological characteristics which help through the stage of planning and production. In the present study, an attempt has been done on two phosphate deposits at Elsebaiya area on both sides of the River Nile namely: Um Tondoba mine at Elsebaiya East area and Western River Nile mine in Elsebaiya West area. Depending on the available data, statistical analysis illustrated differences in the distribution of P2O5 % and ore thickness within the studied areas. Geostatistics used to start with constructing variograms for P2O5 % and thickness for the two phosphate deposits to be used with ordinary kriging models, also constructing cross variograms between P2O5 % and thickness to be used with cokriging models where the difference in the variogram parameters reflected a specific variation for each deposit horizontally and vertically. The ordinary kriging models and cokriging models illustrated different distribution behavior through both the two kriging techniques.