Daily variability of river concentrations and fluxes: indicators based on the segmentation of the rating curve

International audienceThe variability of water chemistry on a daily scale is rarely addressed due to the lack of records. Appropriate tools, such as typologies and dimensionless indicators, which permit comparisons between stations and between river materials, are missing. Such tools are developed here for daily concentrations (C), specific fluxes or yields (Y) and specific river flow (q). The data set includes 128 long-term daily records, for suspended particulate matter (SPM), total dissolved solids (TDS), dissolved and total nutrients, totalling 1236 years of records. These 86 river basins (103-106 km2) cover a wide range of environmental conditions in semi-arid and temperate regions. The segmentation--truncation of C-q rating curves into two parts at median flows (q50) generates two exponents (b50inf and b50sup) that are different for 66% of the analysed rating curves. After segmentation, the analysis of records results in the definition of nine major C-q types combining concentrating, diluting or stable patterns, showing inflexions, chevron and U shapes. SPM and TDS are preferentially distributed among a few types, while dissolved and total nutrients are more widely distributed. Four dimensionless indicators of daily variability combine median (C50, Y50), extreme (C99, Y99) and flow-weighted (C*, Y*) concentrations and yields (e.g. C99/C50, Y*/Y50). They vary over two to four orders of magnitude in the analysed records, discriminating stations and river material. A second set of four indicators of relative variability [e.g. (Y*/Y50)/(q*/q50)], takes into account the daily flow variability, as expressed by q*/q50 and q99/q50, which also vary over multiple orders of magnitude. The truncated exponent b50sup is used to describe fluxes at higher flows accounting for 75% (TDS) to 97% (SPM) of interannual fluxes. It ranges from − 0*61 to + 1*86 in the database. It can be regarded as the key amplificator (positive b50sup) or reductor (negative b50sup) of concentrations or yields variability. C50, Y50, b50sup can also be estimated in discrete surveys, which provides a new perspective for quantifying and mapping water quality variability at daily scal

Metal contamination budget at the river basin scale: a critical analysis based on the Seine River

International audienceMaterial 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. A triple integration is performed: space integration over the catchment (65000 km2), time integration for the 1950-2000 trend analysed at 5 year resolution, and a conceptual integration resulting in two F2A indicators. 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%

Incertitudes sur les métriques de qualité des cours d'eau (médianes et quantiles de concentrations, flux, cas des nutriments) évaluées a partir de suivis discrets Uncertainties on river water quality metrics assessement (nutrients, concentration quantiles and fluxes) based on discrete surveys

International audienceL'évaluation de la qualité des cours d'eau est réalisée à partir de deux principaux types d'indicateurs : les concentrations annuelles (moyennes arithmétiques (Cmoy), médianes (C50), quantiles supérieurs (C90), moyennes pondérées par les débits, (C*..) qui sont rapportées à une grille de qualité (SEQ-Eau) et les flux annuels ramenés généralement à la surface du bassin versant productrice. Ces indicateurs sont entachés d'une incertitude, rarement quantifiée, qui dépend d'abord de la variabilité des concentrations des différents constituants avec la saison et les débits, de la variabilité hydrologique et du nombre de mesures N/an. C'est la spécificité du programme VARIFLUX soutenu par le programme ECCO-ANR/INSU/CNRS dont les résultats sont présentés ici. River water quality assessment is commonly based on two types of metrics : i) annual concentrations (annual means, medians, upper percentiles which are compared to water quality scales and ii) annual fluxes, generally normalized to the river basin area (specific fluxes). These metrics, when determined from discrete surveys should be associated with uncertainties, rarely quantifed, which depend : i) on the concentrations variability with water discharge and/or season, ii) on the river flow variability and, ii) on the survey frequency. The VARIFLUX project is addressing these questions from a Monte-Carlo of discrete simulation surveys based on a rare set of daily records (Suspended particulate Matter, MES, total dissolved solids, TDS, nutrients) in France and in the USA

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

Impair-then-Repair: A Brief History & Global-Scale Hypothesis Regarding Human-Water Interactions in the Anthropocene

Water is an essential building block of the Earth system and a nonsubstitutable resource upon which humankind must depend. But a growing body of evidence shows that freshwater faces a pandemic array of challenges. Today we can observe a globally significant but collectively unorganized approach to addressing them. Under modern water management schemes, impairment accumulates with increasing wealth but is then remedied by costly, after-the-fact technological investments. This strategy of treating symptoms rather than underlying causes is practiced widely across rich countries but leaves poor nations and many of the world\u27s freshwater life-forms at risk. The seeds of this modern “impair-then-repair” mentality for water management were planted long ago, yet the wisdom of our “water traditions” may be ill-suited to an increasingly crowded planet. Focusing on rivers, which collectively satisfy the bulk of the world\u27s freshwater needs, this essay explores the past, present, and possible future of human-water interactions. We conclude by presenting the impair-then-repair paradigm as a testable, global-scale hypothesis with the aim of stimulating not only systematic study of the impairment process but also the search for innovative solutions. Such an endeavor must unite and cobalance perspectives from the natural sciences and the humanities

Scientists’ Warning to Humanity: Rapid degradation of the world\u27s large lakes

Large lakes of the world are habitats for diverse species, including endemic taxa, and are valuable resources that provide humanity with many ecosystem services. They are also sentinels of global and local change, and recent studies in limnology and paleolimnology have demonstrated disturbing evidence of their collective degradation in terms of depletion of resources (water and food), rapid warming and loss of ice, destruction of habitats and ecosystems, loss of species, and accelerating pollution. Large lakes are particularly exposed to anthropogenic and climatic stressors. The Second Warning to Humanity provides a framework to assess the dangers now threatening the world\u27s large lake ecosystems and to evaluate pathways of sustainable development that are more respectful of their ongoing provision of services. Here we review current and emerging threats to the large lakes of the world, including iconic examples of lake management failures and successes, from which we identify priorities and approaches for future conservation efforts. The review underscores the extent of lake resource degradation, which is a result of cumulative perturbation through time by long-term human impacts combined with other emerging stressors. Decades of degradation of large lakes have resulted in major challenges for restoration and management and a legacy of ecological and economic costs for future generations. Large lakes will require more intense conservation efforts in a warmer, increasingly populated world to achieve sustainable, high-quality waters. This Warning to Humanity is also an opportunity to highlight the value of a long-term lake observatory network to monitor and report on environmental changes in large lake ecosystems