Global system of rivers: Its role in organizing continental land mass and defining land‐to‐ocean linkages

The spatial organization of the Earth\u27s land mass is analyzed using a simulated topological network (STN‐30p) representing potential flow pathways across the entire nonglacierized surface of the globe at 30‐min (longitude × latitude) spatial resolution. We discuss a semiautomated procedure to develop this topology combining digital elevation models and manual network editing. STN‐30p was verified against several independent sources including map products and drainage basin statistics, although we found substantial inconsistency within the extant literature itself. A broad suite of diagnostics is offered that quantitatively describes individual grid cells, river segments, and complete drainage systems spanning orders 1 through 6 based on the Strahler classification scheme. Continental and global‐scale summaries of key STN‐30p attributes are given. Summaries are also presented which distinguish basins that potentially deliver discharge to an ocean (exorheic) from those that potentially empty into an internal receiving body (endorheic). A total of 59,122 individual grid cells constitutes the global nonglacierized land mass. At 30‐min spatial resolution, the cells are organized into 33,251 distinct river segments which define 6152 drainage basins. A global total of 133.1 × 106 km2 bear STN‐SOp flow paths with a total length of 3.24 × 106 km. The organization of river networks has an important role in linking land mass to ocean. From a continental perspective, low‐order river segments (orders 1‐3) drain the largest fraction of land (90%) and thus constitute a primary source area for runoff and constituents. From an oceanic perspective, however, the small number (n=101) of large drainage systems (orders 4‐6) predominates; draining 65% of global land area and subsuming a large fraction of the otherwise spatially remote low‐order rivers. Along river corridors, only 10% of land mass is within 100 km of a coastline, 25% is within 250 km, and 50% is within 750 km. The global mean distance to river mouth is 1050 km with individual continental values from 460 to 1340 km. The Mediterranean/Black Sea and Arctic Ocean are the most land‐dominated of all oceans with land:ocean area ratios of 4.4 and 1.2, respectively; remaining oceans show ratios from 0.55 to 0.13. We discuss limitations of the STN‐30p together with its potential role in future global change studies. STN‐30p is geographically linked to several hundred river discharge and chemistry monitoring stations to provide a framework for calibrating and validating macroscale hydrology and biogeochemical flux models

Metal contamination budget at the river basin scale: an original Flux-Flow Analysis (F2A) for the Seine River

Material flow analysis and environmental contamination analysis are merged into a Flux-Flow analysis (F2A) as illustrated for the metal circulation in the Seine River catchment. F2A combines about 30 metal flows in the anthroposphere (14 million people) and/or metal fluxes in the environment (atmosphere, soils, and aquatic system) originating from two dozens of sources. The nature and quality of data is very heterogeneous going from downscaled national economic statistics to upscaled daily environmental surveys. <br><br> A triple integration is performed: space integration over the catchment (65 000 km<sup>2</sup>), time integration for the 1950–2000 trend analysed at 5 year resolution, and a conceptual integration resulting in two F2A indicators. <br><br> Despite the various data sources an average metal circulation is established for the 1994–2003 period and illustrated for zinc: (i) metal circulation in the anthroposphere is now two orders of magnitude higher than river outputs, (ii) long term metal storage, and their potential leaks, in soils, wastedumps and structures is also orders of magnitude higher than present river fluxes. Trend analysis is made through two F2A indicators, the per capita excess load at the river outlet and the leakage ratio (excess fluxes/metal demand). From 1950 to 2000, they both show a ten fold improvement of metal recycling while the metal demand has increased by 2.5 to 5 for Cd, Cu, Cr, Pb and Zn, and the population by 50%

Flux of nutrients from Russian rivers to the Arctic Ocean: Can we establish a baseline against which to judge future changes?

Climate models predict significant warming in the Arctic in the 21st century, which will impact the functioning of terrestrial and aquatic ecosystems as well as alter land‐ocean interactions in the Arctic. Because river discharge and nutrient flux integrate large‐scale processes, they should be sensitive indicators of change, but detection of future changes requires knowledge of current conditions. Our objective in this paper is to evaluate the current state of affairs with respect to estimating nutrient flux to the Arctic Ocean from Russian rivers. To this end we provide estimates of contemporary (1970s–1990s) nitrate, ammonium, and phosphate fluxes to the Arctic Ocean for 15 large Russian rivers. We rely primarily on the extensive data archives of the former Soviet Union and current Russian Federation and compare these values to other estimates and to model predictions. Large discrepancies exist among the various estimates. These uncertainties must be resolved so that the scientific community will have reliable data with which to calibrate Arctic biogeochemical models and so that we will have a baseline against which to judge future changes (either natural or anthropogenic) in the Arctic watershed

Geochemistry of the sahelian Gambia river during the 1983 high-water stage

La géochimie des rivières africaines est très peu connue comparativement à celle des fleuves des autres continents. Cette étude sur le cours moyen de la Gambie complète les récents travaux de Lesack et al. (1984-1985) dans la partie aval du fleuve et ceux de Gac et al. (1987) sur le haut bassin guinéen. Les flux dissous et de matières en suspension sont évalués à partir de la composition chimique moyenne (44 mg/l) et de la charge solide (47 mg/l). Le carbone organique particulaire représente de 1,2 à 8 % des matières en suspension. (Résumé d'auteur

Rivers of the Anthropocene

This exciting volume presents the work and research of the Rivers of the Anthropocene Network, an international collaborative group of scientists, social scientists, humanists, artists, policymakers, and community organizers working to produce innovative transdisciplinary research on global freshwater systems. In an attempt to bridge disciplinary divides, the essays in this volume address the challenge in studying the intersection of biophysical and human sociocultural systems in the age of the Anthropocene, a new geological epoch of humans’ own making. Featuring contributions from authors in a rich diversity of disciplines—from toxicology to archaeology to philosophy— this book is an excellent resource for students and scholars studying both freshwater systems and the Anthropocene

Incidence and impact on clinical outcome of infections with piperacillin/tazobactam resistant Escherichia coli in ICU: A retrospective study

Escherichia coli infections are frequent in ICU patients. The increased resistance to fluoroquinolones and amoxicillin/clavulanate of this pathogen mandates the prescription of broad-spectrum antibiotics such as piperacillin/tazobactam (PIP-TAZ) or third generation cephalosporins (3GC)

Metal contamination budget at the river basin scale: an original Flux-Flow Analysis (F2A) for the Seine River

International audienc

Diel turbidity cycles in a headwater stream: evidence of nocturnal bioturbation?

Purpose: A small number of recent studies have linked daily cycles in stream turbidity to nocturnal bioturbation by aquatic fauna, principally crayfish, and demonstrated this process can significantly impact upon water quality under baseflow conditions. Adding to this limited body of research, we use high-resolution water quality monitoring data to investigate evidence of diel turbidity cycles in a lowland, headwater stream with a known signal crayfish (Pacifastacus leniusculus) population and explore a range of potential causal mechanisms. Materials and methods: Automatic bankside monitoring stations measured turbidity and other water quality parameters at 30-min resolution at three locations on the River Blackwater, Norfolk, UK during 2013. Specifically, we focused on two 20-day periods of baseflow conditions during January and April 2013 which displayed turbidity trends typical of winter and spring seasons, respectively. The turbidity time-series, which were smoothed with 6.5 hour Savitzky-Golay filters to highlight diel trends, were correlated against temperature, stage, dissolved oxygen and pH to assess the importance of abiotic influences on turbidity. Turbidity was also calibrated against suspended particulate matter (SPM) over a wide range of values via linear regression. Results and discussion: Pronounced diel turbidity cycles were found at two of the three sites under baseflow conditions during April. Spring night-time turbidity values consistently peaked between 21:00 and 04:00 with values increasing by ~10 nephelometric turbidity units (NTU) compared with the lowest recorded daytime values which occurred between 10:00 and 14:00. This translated into statistically significant increases in median midnight SPM concentration of up to 76% compared with midday, with night-time (18:00 – 05:30) SPM loads also up to 30% higher than that recorded during the daytime (06:00 – 17:30). Relating turbidity to other water quality parameters exhibiting diel cycles revealed there to be neither any correlation that might indicate a causal link, nor any obvious mechanistic connections to explain the temporal turbidity trends. Diel turbidity cycles were less prominent at all sites during the winter. Conclusions: Considering the seasonality and timing of elevated turbidity, visual observations of crayfish activity, and an absence of mechanistic connections with other water quality parameters, the results presented here are consistent with the hypothesis that nocturnal bioturbation is responsible for generating diel turbidity cycles under baseflow conditions in headwater streams. However, further research in a variety of fluvial environments is required to better assess the spatial extent, importance and causal mechanisms of this phenomenon

Relationship between river size and nutrient removal

Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 33 (2006): L06410, doi:10.1029/2006GL025845.We present a conceptual approach for evaluating the biological and hydrological controls of nutrient removal in different sized rivers within an entire river network. We emphasize a per unit area biological parameter, the nutrient uptake velocity (νf), which is mathematically independent of river size in benthic dominated systems. Standardization of biological parameters from previous river network models to νf reveals the nature of river size dependant biological activity in these models. We explore how geomorphic, hydraulic, and biological factors control the distribution of nutrient removal in an idealized river network, finding that larger rivers within a basin potentially exert considerable influence over nutrient exports.This work was funded by NASA-IDS (NNG04GH75G), NSF-LTER OCE-9726921, and NOAA (NA17RJ2612- 344 to Princeton U.)