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Introduction Natural Flood Management (NFM) measures can regulate floods in a catchment and provide additional benefits like increasing biodiversity, improving soil and water quality, carbon sequestration, decreasing soil erosion, increasing agricultural productivity and improving public health and well-being. Previously, NFM measures were mainly modelled using lumped approaches which do not take into account the spatial distribution of the area in question. A distributed hydrological model makes use of areas with the same hydrological behaviour called Hydrological Response Units (HRUs), which can be divided to represent distributed NFM measures in the catchment. It is also able to represent key catchment processes like subsurface flow and overland flow pathways efficiently. This study will utilise a version of the HBV-96 distributed model built in Python 3.6, and whose implementation follows the HBV-96 model of Lindstrom et al. (1997). The NFM measures will be represented as units in the different sub basins of the catchment and the effect of these measures on the neighbouring cells will be examined. The effect of the measures on the peak stream flow and attenuation of the flow hydrograph will also be examined at key locations within the catchment. The research is centred on the Littlestock Brook, a rural catchment of about 16km2 located in West Oxfordshire, United Kingdom. Littlestock Brook is a tributary of the River Evenlode, which is in turn a tributary of the River Thames. A programme of NFM measures including storage ponds, hedge rows and bunds is currently being implemented in the Littlestock Brook. (Ramsbottom, 2017). The study sets out to represent, calibrate, validate and implement a fully distributed hydrological model of the catchment with the NFM measures. The model focuses on the effect of the NFM measures on the peak flow hydrograph and the timing of the peak.The effect of NFM measures can be investigated by modifying model parameters to represent runoff attenuation features like storage areas, soil structure, infiltration, surface roughness and canopy evaporation.Study Objectives The study seeks to address:a) how NFM measures can be incorporated in a fully distributed hydrological model; b) the effects of NFM measures on flood peak hydrographs ; and c) how the representation of NFM measures affects the neighbouring cells in the catchment.Material and Methods The fully distributed model is currently under development to represent and study the effect of NFM measures on flood peaks. The main model inputs are: precipitation, air temperature, potential evapotranspiration, flow direction and flow accumulation maps which can be extracted from the topography map using the ArcGIS reference system.Expected study results The study is specifically expected to: (i) identify catchment characteristics that could enhance performance of NFM measures ; (ii) demonstrate the effect of NFM measures on flood peak hydrographs; (iii) indicate how changes in the catchment affect other processes in the neighbouring cells. The insight on inundation areas, the effect on the flood peak and the timing to peak the results can be used to develop an optimized strategy to reduce flood risk downstream in similar catchments. [ABSTRACT FROM AUTHOR]

Characterization of groundwater-surface water interactions remains challenging,especially in anthropogenically affected and geologically complex river systems. In thisstudy, groundwater inflow into the Ammer River was quantified by optimizingexfiltration rates in an implicit numerical model (FINIFLUX) to measured data ofseveral environmental tracers (e.g., sulfate (SO42−), radon (222Rn)) and organicconservative pollutants like carbamazepine and sulfamethoxazole emitted via awastewater treatment plant (WWTP). Modelling results of the selected tracers werecompared. The investigated Ammer River is strongly karstified and anthropogenically modified (millcanals, weirs, numerous artificial inputs) but representative for many small river systems inEurope. 222Rn activities in the river ranged from 500 to 3300 Bq m−3 and SO42−concentrations from 224 to 291 mg L−1. Concentrations of carbamazepine (90-130 ng L−1)and sulfamethoxazole (55-100 ng L−1) in the river water result from effluents of aWWTP. All tracers indicate major local groundwater inflows over the 6 km riverreach. Additional high peaks mainly observed in 222Rn activities indicate inputsalong geological fault lines, whereby increasing concentrations of carbamazepineand sulfamethoxazole may be attributed to inputs of groundwater contaminated byinfiltration of wastewater from a nearby WWTP. 222Rn-based calculations showed thebest optimization performance (R2=0.90) and result in a reasonable cumulativegroundwater inflow of 0.274 m3 s−1 (28.5% of total discharge) for the investigated reach.Poor optimizations for the other tracers may be due to the diurnal pattern of ionconcentrations induced by the WWTP and measurement uncertainties and the smallconcentration differences between river water and groundwater for carbamazepine andsulfamethoxazole. In our case study, 222Rn seems to be the most suitable environmental tracer despiteuncertainties in degassing and determination of the groundwater endmember concentration.However, only a multi tracer approach can account for the complexity of the investigatedriver system and may thus be indispensable for future investigations aiming to understandgroundwater-surface water interactions. [ABSTRACT FROM AUTHOR]

The transport of coarse sediment during floods often exhibits hysteresis patterns from changes in flow fields, channel geometry, bedforms, or sediment supply conditions. Flume experiments that simulate hydrographs tend to confirm that hysteresis is a consequence of the progressive organization of surface sediments in terms of grain protrusion, imbrication, orientation, and roughness. Hysteretic patterns are also highly dependent on the kind of sediment supply conditions, and the type of simulated hydrograph. A factor that has not been investigated extensively is the effect of the timing and sequencing of floods on bedload transport. Depending on its magnitude and duration, each flood leaves the channel bed in a different condition, which influences the bedload transport of the next event, representing the river bed's memory of past floods, which can determine future responses to natural disturbances. In this study, I investigated the effects of different sequences of events, i.e., the flood history, on sediment transport through a series of flume experiments that simulated three types of stepped and symmetrical hydrographs (ranging from short-duration/high-magnitude to long-duration/low-magnitude events) under sediment recirculation conditions. Hydrographs were simulated as a sequence of the same event, and with events in different sequences, in order to explore the effects of different antecedent conditions on sediment transport. The results show that a previous event decreases the rates of sediment transported by a certain hydrograph by around 40% if a high-magnitude event precedes another one and around 70% if a low-magnitude event precedes another event of similar magnitude. A low-magnitude event does not affect the rate of sediment transported by a subsequent high-magnitude flood, but a high-magnitude event reduces the sediment transported by a subsequent long-duration/low-magnitude event. [ABSTRACT FROM AUTHOR]

River network structures are known to be scale-invariant, characterized by Horton scalingratios, and power-law relations between geomorphological variables (e.g., Hack’s law). Rivernetworks also manifest scaling character for their functions, such as hydraulic geometry, orin-stream nutrient uptake processes. Human-related variables (e.g., human settlements) alsoreveal globally consistent scale-invariance over stream orders within a river basin. Based onscaling properties of river networks, recent work demonstrated scaling of dissolvedorganic carbon removal at the basin-scale (exported from diffuse sources). Ourrecent study showed that point-source nutrient loads discharged from wastewatertreatment plants (WWTPs) exhibited scaling properties in three large river basins inGermany. In the current study, we link these scaling ideas to investigate how spatiallyheterogeneous nutrient loads discharged from multiple urban point sources (i.e.,WWTPs) scale across urbanized basins. Available data from three German riverbasins for size distribution and locations of WWTPs are used to determine scalingof nutrient loads based on stream order hierarchy and spatial patterns based onGeomorphologic Width Function approach. Nutrient loads from spatially heterogeneouspoint sources are super-imposed in diffuse nutrient loads to produce spatially heterogeneouspatterns of nutrient concentrations. We examine the joint contribution of hydrologicdilution and in-stream processes to the emergent scaling across the entire basin ofwater-quality impairments (nutrient concentrations exceeding specified thresholds). [ABSTRACT FROM AUTHOR]

The post-glacial adjustment of streams can be described as a battle between two geomorphic giants: the magnitude and resistance of the glacial imprint and the competence of subsequent fluvial flows. In northern Fennoscandia, which deglaciated ~9500 y BP, the outcome of this battle provides both insight into poorly studied high-latitude regions and a glimpse into the trajectory of currently deglaciating regions. The glacial signature of eroded bedrock and deposited till in this region have organized tributary stream networks into three distinct process domains: lakes, slow-flowing reaches (S0<0.1% in peat/ fine sediment), and rapids (S0: 0.1-7% with gravel to boulder beds). Thus, these post-glacial streams have two characteristics that complicate a process-based understanding of channel form and sediment transport: (1) they are typically semi-alluvial, in that they contain coarse glacial legacy sediment, and (2) mainstem lakes buffer sediment and water fluxes. Here, I present research to constrain controls on channel geometry and sediment transport in semi-alluvial rapids at three scales: (1) the particle-scale, quantifying sediment transport with a field tracer study, (2) the reach-scale, determining the potential for bedforms or sediment clusters through a flume experiment, and (3) the catchment scale, examining downstream variations in width using GIS-based analyses.Sediment particle dynamics within five semi-alluvial rapids (S0: 2.1-7%) were quantified using RFID-tagged tracer clasts. After a large snowmelt flood (>Q50), median transport distances for D10- to D50-sized clasts were <0.1 m, with no clear relationship between slope or shear stress and transport distance. Rather, as previous studies in boulder-bed mountain streams show, boulder protrusion and grain resistance likely play a greater role, increasing critical shear stress and reducing sediment transport. Based on a flume study mimicking reach-scale conditions of semi-alluvial rapids, it is clear that large clasts (>D84) are basically immobile and do not adjust to form step-pool features. But patterns of deposition and scour around boulders exist, with more deposition upstream of boulders at higher flows. Most geomorphic work is done at low and intermediate flows (Q2-Q10), with little additional transport at Q50 flows, which has a relatively low magnitude due to lake buffers. To determine whether channel width has adjusted to contemporary flow regimes at the catchment scale, downstream variation in bankfull width was analyzed in two medium-sized catchments. Regressions of width vs. drainage area (derived from 2m DEMs) have low explanatory power (R2: 0.05-0.5); coefficients (α) are low (<1) and regression exponents (β) show wide variation (0.26-0.75). Instead, spatial variability in till deposits and peat formation likely control channel width. While these semi-alluvial streams in stream-lake catchments are technically in equilibrium, as they are not aggrading or degrading, their stable channel geometry does not reflect the contemporary landscape sediment yield or hydroclimatic regime. Past studies have shown that bedrock river gorges in northern Sweden formed during deglaciation with little Holocene erosion. Similarly, tributary channels with coarse glacial sediment and mainstem lakes are frozen in time, reflecting catchment- and reach-scale morphologies shaped during high flows at deglaciation, with contemporary adjustment occurring only at the particle to sediment-cluster scales. [ABSTRACT FROM AUTHOR]

Diverse empirical (data-driven) and theoretical (model-driven) studies have shown that the peak flows associated to a probability of exceedance or a specific rainfall-runoff event scales with respect to drainage area. This hydrologic feature is well-known as flood scaling and it has been widely used by the hydrologic community in peak flow regionalization. In theoretical ideal conditions with spatial and temporal uniform fields of soil moisture and rainfall, the flood scaling seems to hold perfectly, however the actual heterogeneities of these fields create new peak flow variabilities that cannot be explained just with drainage area. This study investigates the actual variabilities of rainfall fields, soil moisture fields, and river network structure in the peak flow scaling of 52 rainfall-runoff events that were observed in the Iowa River Basin. The spatial and temporal variability of the rainfall and soil moisture were quantified using radar and satellite data respectively, and the river network structure was described through Width Function Descriptors. We demonstrate that these variabilities can be used to improve regional peak flow regressions using a physics-driven by providing justification for the inclusion of explanatory variables to be used on regionalization studies. Finally, we connect the results of rainfall-runoff events with peak flow quantiles, showing that regional regression of peak flow quantiles can be improved as well. [ABSTRACT FROM AUTHOR]

River channels and their adjacent hyporheic zone, floodplain, and ponded waters continually exchange mass and energy. When these exchange processes are in harmony, we expect an amplification of their biogeochemical effects, and therefore a more prominent role modulating water quality at the local and watershed scales. Discordance, on the other hand, is expected to attenuate the effects of connectivity. In this work, we used the model Networks with EXchange and Subsurface Storage (NEXSS) to assess when and where these exchange processes are in harmony along rivers within the continental United States. Using a simple routing scheme, we translate estimates of fluxes and residence times into a cumulative measure of river corridor connectivity at the watershed scale, differentiating the contributions of hyporheic zones, floodplains, and ponded waters. We find that the relative role of these exchange subsystems changes seasonally, driven by the intra-seasonal variability of discharge. Also, we find that the interplay between exchange processes varies with location, typically characterized by discordance in low-order streams and harmony in high-order rivers. Understanding the competing nature of exchange processes is critical to represent connectivity in physics-based models for water quality and to design, implement, and evaluate sustainable water management practices at the scale of the nation. [ABSTRACT FROM AUTHOR]

Guide reach is located at the edge of the source zone of Yellow River, downstream of the first large dam along the trunk stream. The closure of Longyangxia Dam in 1986 permanently altered the flow regime in Guide reach. Two smaller dams upstream of Guide reach, Nina Dam constructed in 2003, and Laxiwa constructed in 2009 had a minor influence on the flow regime. Satellite imagery is used to assess channel planform adjustments from 1975-2015. Historic annual flow regime changes in terms of magnitude, duration, timing, frequency and rate of changes were analysed using the IHA model. Field surveys analysed the current distribution of riparian species and relations to channel geomorphological patches in 2017. Flow regulation transformed this dynamic braided-anabranching river, reducing channel multiplicity, reducing the width of the active channel zone, aggregating instream bars into much larger compound structures, and creating large floodplain areas (most of which have been further manipulated by human activities). Riparian vegetation become more stable and complex. Multiple regression analysis showed that the 1-year interval flood and the 90-day last high flow exert a significant influence upon rates of channel deposition and erosion respectively. In addition, the 3 year interval flood exerts a key impact of vegetation erosion. Relative to regulated rivers in other parts of the world, changes to the flow regime have influenced geomorphic adjustments to a greater degree than vegetation adjustments, suggesting that mutual interactions between geomorphic processes and riparian vegetation have exerted a reduced influence in this instance. [ABSTRACT FROM AUTHOR]

Heat transport within the hyporheic zone strongly affects biogeochemical reactions, and therefore it plays a fundamental role in ecological services, river management, and habitat restoration. With this in mind, we perform a systematic analysis to gain a mechanistic understanding of how the variability of river discharge and temperature impact flow and transport within bedform-driven hyporheic zones. We used time series of river discharge and temperature for stations along the Mississippi River Basin, which are characterized by different degrees of regulation, to force a physics-based model of the hyporheic exchange process. Our modeling results indicate that coupling flow and heat transport significantly affects the dynamic response of hyporheic zones, resulting in substantial differences in the exchange rates and characteristic timescales. We also find that the hyporheic zone acts as a low-pass filter, removing high-frequency temperature oscillations. The importance of this filtering effect depends on the characteristic timescales for surface discharge and temperature variability (the driving forces) and the hyporheic zone's transport timescale (the modulator). This work has important implications for understanding local variability in hyporheic exchange and its implications for thermal refugia and ecosystem functioning. [ABSTRACT FROM AUTHOR]

Improving the accuracy of flood forecasting is critical in reducing the damage that can occur during flood disasters. In Japan, the flood prediction system is in operation in the first class rivers – relatively large and important rivers. However, small rivers, especially urban rivers, are so difficult to predict the river stage because of the quick rainfall-runoff responses. Such rivers are regarded as difficult to deliver the real time information on flood risk.Recently in Japan, X-band radar rainfall data can be used in real-time prediction for operation. X-band radar is highly resolution in both spatially and temporally. Furthermore, deep learning model has been applied to the river stage prediction and confirmed to have a good accuracy. By applying the X-band radar data to the deep learning model, river-stage prediction could be possible to the urban small rivers.In this study, we developed the deep learning river stage prediction model using the x-band radar rainfall data. We applied the model to the small urban rivers in Tokyo and confirmed the good prediction result. [ABSTRACT FROM AUTHOR]

To predict the behavior of particulate and dissolved radiocesium (137Cs) in river water, somesoil and land use categories in the watershed should be considered because these may affectthe dissolved 137Cs concentration. This recommendation is based on measurements madeafter the Chernobyl accident (Smith et al., 2004). However, it is difficult to predict thedissolved 137Cs concentration in Japanese rivers based only on studies after theChernobyl accident because 137Cs dynamics differ between the areas surroundingthe Chernobyl and Fukushima Daiichi Nuclear power plants because of climateand soil differences (Evrard et al., 2015; Konoplev et al., 2016). In this study, toinvestigate the factors that affect dissolved 137Cs concentrations in Japanese rivers, wemeasured dissolved 137Cs concentrations in 67 rivers under baseflow conditions 13–280km from the Fukushima Daiichi nuclear power plant in August and September2017. The watershed area of each sampling point was 3.2–3,600 km2 and the averaged 137Csinventory for each watershed in July 2011 was 4.7–1,700 kBq/m2(calculated from the 137Csinventory distribution map by Kato et al., under review). Land use in the watersheds variedand included forest watershed (up to 99% forest area) and urban watershed (up to 73%building area). To research the influence of water quality on the dissolved 137Csconcentration, we coincidentally measured the main coexisting solutes, pH value,and electric conductivity in the river water. Additionally, to research the effect ofthe 137Cs source, the land use ratio, soil components, and watershed topographicwetness index were calculated from geographic information data published on theInternet. The dissolved 137Cs radioactivity concentrations in river water were 0.10–120 Bq/m3andstrongly depended on the averaged 137Cs inventory in the watershed (r = 0.70, p &#x003C; 0.01).Therefore, the dissolved 137Cs concentration was normalized by dividing it by theaveraged 137Cs inventory (converted into the range 4.5×10−6–2.2×10−3 m−1) and thecorrelations among these values and each water quality factor and 137Cs source wereanalyzed. Significantly high positive and a negative correlation existed between the normalizeddissolved 137Cs concentration and building area ratio (r = 0.78) and forest area ratio (r =-0.60), respectively. The high concentration of coexisting ions in the water was a cause ofsuch a high correlation because it would impede 137Cs absorption in soil particles because thebuilding area ratio has a high positive correlation with electrical conductivity (r = 0.55). [ABSTRACT FROM AUTHOR]

Stream-groundwater mixing zones are well known for their importance in biogeochemical reactions linked to enhanced water quality, as for example in river bank filtration processes and in natural attenuation of contaminants. The spatial and temporal exchange patterns between a stream and its connected riparian groundwater were assessed to evaluate the potential reactivity for redox-sensitive compounds like dissolved oxygen (DO) and nitrate under different seasonal and hydrologic conditions. Spatial pattern of stream water infiltration were obtained using time-lapse crosshole geophysics for the detection of EC contrasts during salt tracer tests under various hydraulic conditions. In addition, a numerical groundwater model was set up and calibrated against groundwater heads and tracer test data.Our results reveal that the riparian aquifer is a highly dynamic system with flow directions and travel times changing depending on river discharge. Travel times are better correlated with the slope of the rising limb of discharge events (ΔQ/Δt) than with absolute discharge values. DO consumption increases with increasing temperature and with increasing travel time of the infiltrating river water. We also observe a minor DO enrichment ca. 20 m apart from the river, likely by reaeration through the shallow vadose zone. Higher DO consumption rates are observed within first few meters from the river (up to 70%) most likely linked to the dissolved organic carbon delivered by infiltrating stream water (Stream: 3-15 mg/l; GW: 2mg/l). While discharge peaks result in shorter travel times, the effects on DO consumption seem to be inferior in comparison to temperature. The width of the aerobic zone in the riparian aquifer is enlarged by peak discharge events, reducing the potential for anaerobic reduction of nitrate.With our time and space resolved approach we were able to show that a combination of hydraulic conditions and seasonal temperature pattern shape the dynamic reactivity in the riparian groundwater, depicting its relevance and the extent of its influence for the entire aquatic ecosystem. [ABSTRACT FROM AUTHOR]

The general purpose of the study is to increase knowledge on bedload sediment dynamics in steep mountain streams. In particular, we aim to: (i) evaluate hydrologic thresholds for bedload entrainment; (ii) constrain volumetric bedload transport rates in relation to varying sediment supply and hydro-meteorological forcing. Study sites are Rio Grigno (contributing area at study reach = 7 km²), and its tributary Rio Tolvà (7 km²) in Valsugana and Rio Val Ussaia (2.3 km²) in Val di Sole. They are all step-pool and boulder-cascade channel reaches underlain by granitoid lithology. Grigno and Tolvà are characterized by higher Mean Annual Precipitation (MAP = 1511 mm) than in in Ussaia (MAP = 844 mm). In terms of sediment supply, study reaches in Grigno and Tolvà are decoupled from hillslope sediment inputs, whereas Ussaia is strongly fed by actively eroding till mantled slopes. Median channel slope in the study reaches is 7.5 % in Grigno, 10 % in Tolvà, and 12 % in Ussaia.During the study period, which lasted from December 2013 to December 2016, we monitored precipitation, water discharge and the travel distance of 761 PIT tags (211 in Grigno, 199 in Tolvà and 351 in Ussaia). B-axis of tracer particles ranged from 31 mm to 149 mm. Particle tracking was performed through post flood field surveys using RFID (Radio Frequency Identification) portable antennas. Cumulatively, we conducted 27 surveys in Rio Grigno, 22 in Rio Tolvà, and 28 in Rio Ussaia. Volumetric bedload transport rate for each inter-survey period was calculated by integrating peak flow competence (to establish threshold of motion) and the virtual velocity method on the active channel bed. We classified the hydrologic regime of each inter-survey period in snowmelt (S), rainfall (R) and mixed (M).Monitoring year 2014 was the wettest: 2730 mm in Grigno and Tolvà, 1540 mm in Ussaia. By contrast, monitoring years 2015 and 2016 were much drier, in line with the respective long-term annual means: 1357 mm in Grigno and Tolvà, and 799 mm in Ussaia (2015); 1484 mm in Grigno and Tolvà, and 832 mm in Ussaia (2016). This variability in hydro-meteorological forcing enabled us to investigate a wide array of bedload transport regimes.Preliminary results show that bedload transport chiefly occurs in rainfall-dominated periods (90% in Grigno-Tolvà; 94% in Ussaia), with snowmelt accounting for only 2% (Grigno-Tolvà) and 5% (Ussaia) of the total bedload volume. Despite much wetter conditions in Grigno-Tolvà than in Ussaia, estimated annual bedload volumes in the three monitoring years display consistently much higher values in the latter: 1) 2014: 56.9 m³ in Grigno, 26.3 m³ in Tolvà and 355 m³ in Ussaia; 2) 2015: 5.7 m³ in Grigno, 1 m³ in Tolvà and 53.9 m³ in Ussaia; 3) 2016: 7.2 m³ in Grigno, 1.5 m³ in Tolvà and 11.1 m³ in the Ussaia. We propose that these patterns of contrasting channel bed stability are chiefly associated with different styles and rates of hillslope sediment supply. [ABSTRACT FROM AUTHOR]

Large rivers integrate the products of physical erosion and chemical weathering in different forms (dissolved, fine to coarse particles). The geochemical composition of these products carry important informations on the mechanisms controlling erosion and weathering at the basin scale : sources of the products, vegetation, climate, anthropogenic and tectonic factors, timescale involed. In the framework of a large franco-chinese project, the four largest rivers in China (Changjiang, Huanghe, Zhujiang, Heilongjiang) were sampled : vertical profiles, surface tributaries, bedload sediments and surface monthly time series over a year were collected at different locations along the stream of these rivers. We report major and trace elements concentrations and Nd-Sr isotopes in the suspended particulate matter and bedloads. The four river basins cover a large diversity of climatic, lithologic, tectonic and anthropic settings, that our results put in perspective as controls on erosion-weathering mechanism and its associated timescales. [ABSTRACT FROM AUTHOR]

Plastic pollution of the world's oceans has received widespread attention by the public, media and academics, yet there have been limited efforts to understand how macro- and microplastics (with sizes of less than 5 mm) are actually reaching the sea. The delivery mechanisms, as well as the fate, transport and impact of microplastics on freshwater ecosystems thus remains largely unknown.This study aims to provide an overview of the global distribution of microplastics in freshwater ecosystems, using newly developed standardised sampling protocols and extraction methods. This will allow, for the first time, directly comparable results of freshwater and sediment samples between locations and the analyses of regional differences in the composition of primary (designed) and secondary microplastics (resulting from macro-plastic breakdown). This will thus allow us to define what 'environmentally' relevant' means in the context of microplastic abundance in freshwaters.We present initial results from the Global 100 Plastic Rivers project that deploys a global scientific community approach to provide the first global overview of microplastic distributions in the waters and sediments of rivers, lakes and estuaries. These unprecedented global analyses are enabled and supported by advances in analytical capabilities. In particular, with regards to microplastic extraction and characterisation technologies, recommendations will be presented for international standardisations in sampling and sample extraction, supporting the end goal of a much-needed comprehensive overview of the hydrodynamic and biophysical controls of microplastic transport, accumulation and decay. Elucidation of the global composition and transport behaviour of microplastics will be combined with analysis of their environment specific chemical fate, their ageing and biological (in particular biofilm and eco-corona) interactions and of their adsorption with organic and biological contaminants. This is achieved via controlled exposure treatments carried out in multiple re-circulating artificial river laboratories, simulating a wide range of hydrodynamic and environmental conditions. The preliminary results of this study enable an initial risk assessment of potential entry points into aquatic and terrestrial food webs and thus, of environmental and public health risks. [ABSTRACT FROM AUTHOR]

As part of the preliminary design studies of a new bridge over the River Paraná, Argentina, toconnect the cities of Resistencia and Corrientes, a hydrodynamic and sedimentologic modelwas developed to assess the erosion risks at the structure and define foundation levels. Atthis section, the River Paraná drains a catchment of over 2M km2 and presents analluvial floodplain width of 25 km, with an average yearly discharge of 15,000 m3/s(Drago, 1998). Although these figures are already quite unique, the morphologicalcharacteristics of this site are exceptional due to the very high sediment load provided bythe River Paraguay. It is estimated a mean discharge of 250 mg/l (Drago, et al,1998) of solid material is transported, characterizing the alluvial system from theconfluence with this tributary down to the Delta of the River Paraná, about 800 kmdownstream. The solid material transported through this section is mainly constituted of finesand and lime (Amsler, et al, 2009) whilst the mobile bed in predominantly formedby sands that can form dunes of up to 12 m high (Drago, 1977). Driven by thesediment load characteristics and the average hydraulic slope, the Middle Paranápresents a braided pattern with a fringing floodplain, with high rates of movementand formation of bars and islands, thalweg shifting, erosion and deposition, andbedforms. Geotechnical investigations were run on the future location of the bridge, through severalpit holes, and in addition to a vast literature review, permitted the selection of the appropriateparameters for the modelling application. Steady and unsteady simulations were run on apseudo-3D morphodynamic model, which permitted to represent the detailed hydrodynamicinteraction between the main channel and the floodplain, whilst calculating themorphodynamic evolution in the domain. The main difficulties proved to be validating the obtained results and deciding the scourdepths at the bridge site. This depth will define the foundation positions and therefore, thetechnical and economic viability of the project. Sensitivity runs considering differentcharacteristics of the sediments proved to have small effects on the total scour and depositionrates. The amount of available sediment was decided it will be limited by the presence of ahighly-compacted sand bed layer, located between 10 and 15 m under the existing bed level.Furthermore, given the strong evidence proving that the bed load was constituted by mediumsize sands, the sediment range was represented with only one non-cohesive phase (sand) witha representative d50 of 0.48 mm. The morphodynamic model was run under different scenarios, considering extraordinaryevents (1% and 0.1% of Annual Exceedance Probability) for design purposes, but also underdominant flows (Rayano, 2003) to provide validation scenarios against observed movementof the islands through satellite imagery. [ABSTRACT FROM AUTHOR]

As the Ayeyarwady River approaches the Andaman Sea, it splits into numerous delta distributary channels, which together discharge >108 t/y of sediment to the coastal ocean. This study aims to understand: 1) sediment retention and geomorphic variability through the lower tidally influenced distributaries, 2) deltaic growth along mangrove shorelines, and 3) sediment export through this relatively natural, but rapidly changing deltaic system. We focus on three of the distributary channels that have differing fluvial discharge and marine tidal forcing. There is an order-of-magnitude difference between the discharge carried by the largest of the distributaries, the Yangon River, and the smallest studied, the Bogale River. From east to west, the tidal range at the distributary mouths decreases from ~6 m at the eastern Yangon River, to 3.5 m at central Bogale River, to 3.2 m at the western Pathein River. Seasonal variations are associated with tropical monsoons, and our studies occurred during both high- and low-discharge conditions. During high-discharge conditions, suspended-sediment concentrations (SSC) and sediment dynamics are similar across all three distributary channels. They all carry sediment with a median grain size of 3-4 microns in suspension. During low-discharge, salinity intrusion extends many tens of kilometers upstream of the river mouths, shifting the dynamics within the distributaries from those of a tidal river to an estuary. In this regime, SSC values are observed to decrease in the Pathein River (10s mg/L), while in the Yangon River, SSC increases to >5 g/L. In addition to in-situ data collected during the two seasonal conditions, surface SSC derived from calibrated multispectral remote-sensing products provide a synoptic view of turbidity across the delta, and resolve long-term trends in surface SSC for the distributaries of the Ayeyarwady River. Landsat images suggest greater turbidity toward the apex of the Gulf of Mottama, and in all three distributaries, surface SSC is generally greater near the mouths, and decreases upstream, consistent with our observations. Relating suspended sediment transport in the distributaries to local morphology, we find that channel-bed sediment is primarily muddy sand, but mud deposits can be found in regions of the estuarine turbidity maximum. On the adjacent mangrove-forested intertidal surfaces, morphodynamic studies document sediment-accumulation rates of ~1 cm/yr in the aggrading mangrove forest and prograding subaqueous shoal. Natural networks of dendritic tidal channels within the forest efficiently deliver sediment to intertidal land surfaces distal to the main channels. The mangrove forests of the Ayeyarwady Delta, while diminishing in size due to human factors, are an important sediment sink upstream of the coastal ocean. Due to its large sediment discharge, dynamic seasonal and tidal conditions, and intact mangrove forests, the Ayeyarwady Delta is an important and understudied component of global source-to-sink systems. [ABSTRACT FROM AUTHOR]

A number of studies over the past years have established that seismic data can be used to observe fluvial activity, and that the amplitude of high frequency (>1 Hz) seismic noise in near-river stations can be related to river discharge and bedload transport. Recent theoretical models of seismic noise generation by flow turbulence and bedload impacts provide a framework for understanding how fluvial processes combine to produce observed seismic signals. We use data from a network of seismometers installed in the Bhote Koshi River valley from spring 2015 through fall 2018 to test these models and explore the seismic signals generated by a monsoon-dominated mountain river with typical discharges ranging from approximately 30 to 300 m3/s. We first use a series of event case studies to explore the relationships between fluvial processes and the seismic noise generated in different frequency ranges. These events include temporary damming of the river by an upstream landslide, a local tributary debris flow causing channel constriction, and the aftermath of a glacial lake outburst flood. We find that a reduction in discharge leads to reduced seismic noise over a wide range of frequencies (1-80 Hz), but in near-river (<100 m) stations, the most affected parts of the spectra are a sharp peak at 2-5 Hz and a broad peak at 10-15 Hz. Both of these frequency ranges are sensitive to discharge, but appear to reflect different processes in the river, as they respond in different ways to changes in channel geometry. At even higher frequencies, seismic noise is sensitive to both bedload transport and water discharge. Events that caused an increase in sediment supply in the river are associated with a change in the shape of the frequency spectra and the development of a broad hump at 30-50 Hz, supporting model predictions that this frequency range is sensitive to bedload transport. However, throughout much of the observation period, this 30-50 Hz hump is not visible and noise in this frequency range appears to be dominated by turbulent flow, even in stations 20-50 m from the river, possibly reflecting limited bedload transport at rates well below the river's transport capacity. We then use the existing theoretical models to do a Monte Carlo inversion of the seismic data for water depth and bedload flux over the 2015 monsoon season. The inverted water depth is consistent with pressure gauge data, but we have lower confidence in the bedload flux inversion. Our observations from the Bhote Koshi illustrate the viability of seismic monitoring of discharge, but highlight the difficulty of seismic detection of bedload transport in rivers that are well below transport capacity. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the isotopic composition of δ18O and δ2H inprecipitation and river water from the northwestern part of Romania. All precipitationsamples are used to define Local Meteoric Water Line (LMWL), the relationship between theisotopic composition of precipitation and river water and between δ18O and deuteriumexcess, the relationship between stable isotopic variability in precipitation and moistureorigins. For this study, we collected monthly samples of water precipitation fromsix stations: Vatra Dornei, Gura Haitii, Campulung Moldovenesc from October2014 until Jun 2015, and from Rarau, Suceava and Bistrita-Nasaud stations fromMarch 2012 until December 2017. River water was collected from Moldova River atCampulung Moldovenesc station from October 2014 until February 2016. Herewe find that the seasonal δ18O in precipitation is in agreement with the seasonaltemperature variability, as shown by the significant correlation coefficient (r = 0.77) andwhich shows that the temperature is the key controlling factor of δ18O variability inprecipitation water in this region. The Local Meteoric Water Line in the Northeast part ofRomania is defined by the equation δ2H = 7.79*δ18O +7.46, (r2 = 0.985, n=169). [ABSTRACT FROM AUTHOR]

The quantification of aquifer contribution to river discharge is of primary importance toevaluate the impact of climatic and anthropogenic stresses on the availability of waterresources. Several baseflow estimation methods require river discharge measurements, whichcan be difficult to obtain at high spatio-temporal resolution for large basins. The SWOTsatellite mission will provide water level values from which discharge estimations will bederived for large rivers (&#x003E; 50 - 100 m wide) even in ungauged basins with a maximumfrequency of 21 days. We develop a methodology to estimate baseflow over a whole mission lifetime. To thisaim, an algorithm based on hydrograph separation using the Chapman&#x2019;s filter was developedto automatically estimate the baseflow in a river network at regional scale (&#x003E; 10 000 km2).The algorithm was applied to the Seine River basin (75 000 km2, France) using the dischargetime series simulated at daily time step by the coupled hydrological-hydrogeological modelCaWaQS to obtain the reference baseflow estimations. The same algorithm is then forcedwith discharge time series sampled at SWOT observation frequency. The average baseflow isestimated with good accuracy for all the reaches which are observed at least once per cycle(relative bias less than 8 %). The time evolution of baseflow is also rather wellretrieved, with a Nash-Sutcliffe coefficient above 0.7 for 96 % of the network length(Baratelli et al., 2018). Based on former estimations of uncertainties on dischargesthat will be estimate by the mission, it appears that baseflow estimates are alwaysslightly lower than those on discharge. This work provides new potential for thehydrological community to better close the water cycle using forthcoming spacebornedata. Reference : Baratelli, F., Flipo, N., Rivière, A., Biancamaria, S. (2018) Retrieving riverbaseflow from SWOT spaceborne mission, Remote Sensing of Environment, 218, 44-54.doi:10.1016/j.rse.2018.09.013 [ABSTRACT FROM AUTHOR]

Image-based methods for river volumetric flow rate measurements possess several advantages under complex hydrological conditions. Herein we present two cases where a DischargeKeeper, an image-based system for discharge measurements, has been installed, one at an alpine river and a second one at a wide river.A DischargeKeeper was installed in 2015 at the outlet of the Oberaletsch glacier in Switzerland. The Oberaletsch glacier is located on the southern side of the Bernese Alps, in the canton of Valais at an altitude of 2130 m.a.s.l. It is located within a protected area, therefore it was required that the system has a minimal impact on the environment. Additionally the river is inside of a steep gorge where rockfall is common, therefore the system should be safe from natural hazards. For these reasons it was decided to measure the discharge by means of a non-intrusive method based on image processing. Alpine rivers are characterized by steep slopes, coarse bed material, unstable cross-section, high velocities and turbulence. Under these conditions it is difficult to measure the discharge by means of conventional methods. The system has been taking measurements once an hour, day and night for 4 years during the melt season. For the purpose of verification, but also for system calibration, tracer tests were performed. A sensitivity analysis was performed in order to assess the accuracy of the method under such conditions. The estimated error for the average discharge during the measurement period, was found to have a standard deviation of 0.28m3/s or 4.2%. The system proved to be accurate, robust and cost-effective.The second site is at the Rhine River approximately 20 km before Lake Constance. At this river section, it has a width of around 100 meters. In order to measure such a wide river a Pan Tilt Zoom (PTZ) camera was installed and a DischargeKeeper with a multi-view setup was implemented. By using a PTZ camera, one can zoom to smaller regions of the river surface which allows to have a better resolution of its surface patterns, which are used by the Surface Structure Image Velocimetry (SSIV) algorithm to calculate the surface velocity. To have image sequences with enough resolution of the whole river width, 3 views were chosen, one looking close to the left shore, another one looking to the middle of the river and the third one close to the right shore of the river. Each one of the views are processed independently and once the surface velocities per view are calculated, the information is ensambled to calculate the river discharge in real-time. To calculate the discharge, the river stage is also needed, in this case it was measured optically. For this purpose a fourth view was setup which zooms in to the right shore to identify the intersection between the water line and the bathymetry. This methodology has proven to be very powerful since it can be used in rivers of any width. [ABSTRACT FROM AUTHOR]

Rates of fluvial incision reconstructed for the last 11 Ma from the major E-W fluvial systems of the western margin of the Andes (18°00'S to 20°15'S) highlight the existence of 3 distinct sectors. In Sector 1 (the northernmost part of Chile) the fluvial systems are exoheiric with a terminal base level in the Pacific Ocean and span the Coastal Cordillera, Longitudinal Valley, Precordillera and edge of the Western Cordillera, constraining the uplift of this region to a minimum of ~200 m/Ma (11-7 Ma), 150 m/Ma (7-3 Ma) and 120 m/Ma (3-0 Ma). In Sector 2, to the immediate south, the rivers are shorter and terminate in the Longitudinal Valley, spanning only the Precordillera and part of the Western Cordillera with incision rates of 100-50 m/Ma (11-7 Ma) to 50 m/Ma (7-3 Ma and 3-0 Ma). In southernmost Sector 3 the fluvial systems terminate in the Longitudinal Valley, spanning only the western Precordillera with incision rates of 50 m/Ma (11-7 Ma), 30m/ma (7-3 Ma) and 25 m/Ma (3-0 Ma). Comparison of incision rates between Sectors 1 and 2 constrains the uplift of the Coastal Cordillera to 60m/Ma in keeping with previous studies from the region. Differences between Sectors 2 and 3 (25-50 m/Ma) are attributable to drainage loss by tectonic beheading of catchments by the uplift of the Cordillera de Domeyko fault system. The data suggest that a substantial amount of surface uplift has occurred over the last 11 Ma along the western edge of the Andes which is in agreement with rapid but sustained uplift of the Andes in the Late Miocene. The study highlights the value of regional assessments of fluvial incision for quantitying the impacts and timing of uplift on a continental scale. [ABSTRACT FROM AUTHOR]

Rivers are a transition system for contaminants, which are adsorbed to fine sediments. (Re-) Mobilization, transport and accumulation are the controlling factors in fluvial systems, which influence the processes of relocation and sedimentation. Contaminants can be stored during a long time in depositional areas such as floodplains or at the riverbed until further remobilization takes place. In this study, pollution profiles of three small rivers – Geul, Wurm, and Inde River – with neighboring catchments are compared. The study area is situated within the International River Basin District Meuse (border triangle between Belgium, the Netherlands and Germany) and is part of the oldest cultural landscapes in Europe, influenced by industry and mining. All three rivers are characterized by similar properties like catchment size (~ 350 km²), length (~ 55 km), altitude difference (210 to 260 m), discharge (~ 3.5 m³ sˉ¹ in the lower course), channel width (~ 10 m), and flow regime (perennial and pluvial). Although similarities concerning the natural settings and the land use exist, there are significant differences. The history of all three catchments is closely connected with the occurrence of coal and ore deposits, and varies due to the geological setting. Even though the mining sector disappeared in the study area, there are still dumps and contaminated sites as their legacy. Modern pollution sources like industries, municipal wastewater, and traffic areas became more relevant over time.A resuspension method after Lambert and Walling (1988) was used to collect "suspendible riverbed sediments" from different river reaches. Those sediments are defined as a mixture of recent riverbed sediments coming from the riverbed itself, from the floodplains, and from the hinterland. The suspendible riverbed sediments can be potentially mobilized during flood events. After sampling, the fine-grained fractions (< 63 µm) were analyzed with an energy dispersive polarized Spectro Xepos X-ray fluorescence (XRF) device. Using the eight trace elements Cr, Ni, Cu, Zn, As, Cd, Sn, and Pb, the variability of pollution profiles and contaminant loads are investigated and compared. The comparison of the three neighboring catchments and the identification of potential pollution sources allow to distinguish between natural geogenic background conditions and human impact. The relevance of pollution sources and the differences between them can be observed evaluating the fingerprint of each river. [ABSTRACT FROM AUTHOR]

The hydrology of rivers in the greater Himalayan region is influenced by several confounding factors such as rain, snowmelt, and glacier melt. The precise linkages of these factors to river discharge, however, is not clearly known and continues to be a topic of active research. Here, we use station-based daily river discharge data from Nepal to investigate spatio-temporal characteristics of 22 river catchments with areas ranging from 629 sq km to 43000 sq km in the Nepalese Himalayas. We make the following observations: (1) We find that the deseasonalized time evolution of river discharge in the Karnali basin in west Nepal is different from the rest of the country. The difference in hydrology corroborates existing literature on the Karnali basin - it is climatologically drier and economically poorer with most people living on subsistence agriculture. (2) Our analysis further reveals a nontrivial interannual variability, in particular the occurrence of several anomalously dry spring seasons in which river flow fell to 30% lower than the usual for that time of the year. (3) Further investigation of synoptic-scale climatological factors, which could potentially cause the anomalously low discharge, indicate changes in meridional wind in the north Pakistan region as a possible influencing factor. As an outlook we propose a new West Nepal Discharge Index, which provides a reliable indicator of interannual variability of the Karnali basin, after taking into account intra-seasonal and climatological trends. [ABSTRACT FROM AUTHOR]

High-resolution grid-based hydrological models ask for novel parameter estimation approaches. In this study for the Rhine basin, we estimated the parameters of the wflow_sbm hydrological model with point-scale pedotransfer-functions in conjunction with scaling operators as applied in Multiscale Parameter Regionalization (MPR). Parameters were estimated on the original data resolution, followed by the upscaling of parameter fields to the model resolutions, requiring no further calibration. The approach was tested on a 6-hourly timestep and at four resolutions. Resulting parameter fields and simulated fluxes were assessed on consistency. In addition, results were assessed against discharge observations and LSA SAF actual evapotranspiration (ETact) estimates. We found consistent parameter fields, resulting in ETact and recharge preservation on coarser resolutions. However, no discharge flux preservation was found in smaller basins, which we attribute to model structure and the loss of lateral flow representations on coarser resolutions. Model validation gave KGE-values of >0.7, sometimes >0.85, at many discharge gauging locations, except for the Alpine region. Also ETact-estimates compared well, both spatially and temporally, with LSA SAF estimates (KGE~0.7). [ABSTRACT FROM AUTHOR]

Dynamics of rivers are governed by a variety of climatological, hydrological and geological processes, and are also increasingly affected by human interference. Data from Earth observation can now provide long enough time-series to identify and quantify variability on seasonal and decadal time-scales, which allows us to better understand drivers in river dynamics. We show that 30-year coverage of satellite imagery, supplementary datasets and the freely available software in Google Earth Engine can now provide valuable insight in pattern dynamics between rivers and within rivers. Key concepts that we extract from the images are river envelopes, defining the area that the river has occupied within the observed time frame, and river occupancy density maps, showing regions with high degree of wetting variability and river plan form changes. These maps can be valuable tools for practical applications such as identifying suitable locations for infrastructure development and identifying hazard areas for floods and bank erosion. We also reflect on how these maps can be supplemented with datasets on geology, land cover, land elevation, infrastructures and population densities to get deeper understanding in the dynamics of the river and its past and potential future impacts. [ABSTRACT FROM AUTHOR]

The dynamic of groundwater flow and the interactions between streams and aquifers can be highly influenced by extreme river stage fluctuations during floods. In groundwater models, extreme events represent a transient state in the boundary conditions which may affect groundwater flow and transport of solutes. The objective of this research is to understand the influence of the river boundary condition in the interaction between surface water and groundwater during a flood event considering a case study (Alz river, Germany). We used MODFLOW-2005 to develop a three-dimensional groundwater flow model. Additionally, MT3DMS and MODPATH were used to simulate dispersive and advective solute transport. Finally, we consider four hypothetical scenarios to evaluate the influence of the river stage and the riverbed conductance over groundwater flow and solute transport. The simulations show a large variability at different phases of the flood event in groundwater flow velocity that are driven by changes in the hydraulic gradient. The transport simulations showed that during flood events also break through curves are highly affected by the change in the river stage conditions, giving evidence that these extreme events should be properly considered to describe groundwater flow and transport processes accurately. [ABSTRACT FROM AUTHOR]

Physical parameters of bedload transport are difficult to measure in natural conditions. Bedload is activated when the flow is above a given threshold. Thus, transport occurs during short period of time in flood conditions during which sampling and measurements are difficult or impossible to realize. Moreover, volume and characteristics of transported pebbles depend of their availability upstream that can evolve with time. In order to estimate the threshold of transport, a camera and water level gauge have been installed on the Capesterre river (Guadeloupe, France), at transition from bedrock to alluvial. The camera takes a one-minute movie of a 30m width portion of the river each hours. The water level is estimated every 30 minutes in non-flooding conditions and every 5 minutes during floods. Images are denoised in order to remove the effect of waves and to increase the visibility trough water. In calm condition water depth is around 0.3m in average and the bed is visible. During floods, water thickness can exceed 1 meter. In that case, the bottom of the river is not visible due to water turbidity. Pebbles have been mapped on the clear images. The size and number of pebbles that were deposited or exported from the study area were estimated and reported according to water elevation for data spanning on one year including two major storms that hit Guadeloupe in September 2017. These results are discussed in terms of threshold of transport and pebbles availability. [ABSTRACT FROM AUTHOR]

There are many camping and recreation area located along two sides of Xiayun creek, Fuxing District of Taoyuan City, Taiwan. Recently, extremely rainfall events frequently occur in Northern Taiwan, local government increasingly cares about people's safety in recreation area during typhoon season.After collecting the information of topographic map, grain size distribution, scale and location of structures of check dam and grounsill. To evaluate the disaster risk, this study uses RiverFlow2D to simulate the rainstorm pattern of different reoccurrence frequency years of the Xiayun-creek watershed.By simulate the situation of the water level rises, to analyze the different river width whether it can affect the camping and recreation area, we can explore the dangerous location and associated precaution works. [ABSTRACT FROM AUTHOR]

Due to its particular position in the middle of the Mediterranean Sea and its complex andsteep orography, the Calabrian peninsula (southern Italy) is frequently affected by severeprecipitation events and is particularly prone to significant ground effects. In the earlyafternoon of August 20, 2018, a storm cell caused a flash flood that affected the smallRaganello Creek, in the northern side of the region, causing 10 casualties at the outlet of theRaganello Gorges, where the extension of the catchment is about 100 km2. Though theregional monitoring network is rather dense, in the surroundings of the disaster site raingauges were not able to measure the very intense and highly localized rainfall. However, thethree-hour Surface Rainfall Total (SRT) provided by a single polarization Doppler radar ofthe Italian National Radar Network showed a storm cell with rain peaks of theorder of 70-100 mm/hour in a small mountain area not covered by the monitoringnetwork. The objective of this work is to evaluate the ability of the state-of-the-artmeteorological/hydrological modelling in simulating the Raganello Creek event using bothone-way and fully-coupled approaches, by means of the WRF/WRF-Hydro modellingsystem. The Advanced Research WRF (ARW) Model, version 3.9.1 is used with two one-waynested domains at the resolution of 10 km and 2 km respectively, while the resolution ofthe hydrological model, based on WRF-Hydro version 5.0, is 200 m. The initialand boundary conditions are provided by the ECMWF&#x2019;s Integrated ForecastingSystem (IFS), in its deterministic forecast version at 9 km resolution. Several WRFsimulations have been carried out, before choosing the best configuration, to testthe impact of the initial conditions, horizontal resolutions and parameterizationschemes. Results show that the model, particularly in its fully-coupled version, is able to predictreasonably well the occurrence of the event both in terms of rainfall, thus identifying thestorm cell, and in terms of hydrological impact, reproducing timely what mighthave been (unfortunately, observed runoff is not available) the event hydrograph. [ABSTRACT FROM AUTHOR]

In order to realize the rational development, scientific management and effective protection of water resources, the Chinese government adopts the water function zoning management system to protect water resources. Over the past decade, the water quality in China has become better, and the most areas whose water quality under the goal of water function zone has become better heading to the goal required by this system. However, water quality in a few areas that was better than the goal has getting close to the goal. As a result, this study presents the concept of the trend balance of water quality based on the water function zoning management system. To verify these trend balance points, this study takes the main stream of the Yangtze River as the research area and the time evolution trend of the Yangtze River water quality was studied based on the analysis of big data. The Dickey-Fuller Test was used to test the stability of the water quality time series. It was found that more than 90% of the river sections whose DO and TP have stabilized, and 60% of the sections whose CODMn, NH3-N, BOD5, Pb, and OIL have stabilized, indicating that the water quality of the main stream of the Yangtze River has a steady trend in time evolution. That proves the water quality of the mainstream of the Yangtze River exists trend balance points, which means the water quality will tend to be an equilibrium state that gradually approaches the control target of this system and ultimately fluctuates up and down. Keywords: water function zoning management system; the Yangtze River; big data [ABSTRACT FROM AUTHOR]

Guishui river (Beijing, China) is one of the three major rivers feeding the Guanting reservoir, which played a great role in flood control, irrigation and power generation for the city of Beijing. In addition, this watershed is an important water conservation district and the place where the 2022 Winter Olympics will be held. Due to the cold and arid climate on its catchment, the river has always been occasionally intermittent, yet its discharge dropped to its former fraction in the last 15 years. This caused a parallel degradation of aquatic ecosystem and damaged the river's self-purification function. This study investigated a) the impacts of afforestation campaigns against desertification of the region, b) the recent shift in the agricultural crops towards more water-demanding types such as fruits and flowers and the consequent increase in irrigation volumes, and c) the recent climatic variability on stream-flow with two hydrological models, a conceptual and an empirical one. The results suggest that these three factors explain the majority of observed flow deficits. Based on them, recommendations for future sustainable water utilization are formulated. [ABSTRACT FROM AUTHOR]

Historically, daily measurements of phosphorus (P) concentrations have been conducted in eight different Danish streams covering a range of hydrological regimes and catchment properties. Daily phosphorus concentration data exists from six smaller streams draining agricultural catchments and from two larger rivers both being impacted from diffuse and point sources. One of these rivers – the River Odense have a 20 years long time-series including for most of the period data for two P –forms - total P and dissolved inorganic P. Gauging stations were established in all the streams given access to calculated daily data for mean daily discharge from stage/discharge relationships. Data from all streams are analysed statistically for establishing relationships between P-concentrations and discharge – especially looking for seasonal changes in these relationships that might show either mobilization or retention processes for P. Moreover, a Monte-Carlo assessment of the importance of discrete sampling for P load estimation is conducted for all individual streams and the outcome linked to catchment properties such as size, point sources, land use, etc.+ [ABSTRACT FROM AUTHOR]

The biogeochemical inputs into boreal stream ecosystems depend on terrestrial cycles and catchment hydrology. The near-stream area, or riparian zone, controls the quantity and quality of terrestrial water that becomes stream water. It has been traditionally assumed that diffuse flow is the major pathway for groundwater to reach a stream. However, these diffuse flows are a challenge to detect and quantify, and are often based on debatable assumptions of homogeneity across space and constant rates. This is a problem for closing water, nutrient and energy balances on reach scales. Is there an easy, field-based way to approximate the terrestrial water inputs into a stream reach? Topographic maps allow to easily identify locations across the riparian zone where terrestrial water accumulates before it transitions to the aquatic system. The majority of the catchment's groundwater and event-water (or a combination) routes towards these focal points in the riparian zone from where it is ultimately delivered to the stream. Such points in the landscape provide an opportunity to monitor the dynamics of terrestrial inputs into streams. We refer to these areas as discrete riparian inflow points (DRIPs). We were able show the hydrological and thermal effect of DRIPs on a stream reach over different seasons. Furthermore, we have found that DRIP water has a unique biogeochemistry that stands out from the rest of the riparian zone. We combined biogeochemical data with GIS metrics and field-based measurements to understand the role of DRIPs in a boreal landscape. Using mixed effect models we identified landscape characteristics that explain the biogeochemistry of DRIPs across space and time. Ultimately, we aim to be able to explain the majority of biogeochemical and hydrological dynamics in the low order branches of a stream network, by considering the spatial extend and behaviour of the DRIPs. [ABSTRACT FROM AUTHOR]

The impacts induced by dam on large gravel-bed rivers have been studied for long timeconsidering the morphological and bed alteration responses, but relatively poor knowledgeexists about the modifications occurring in terms of coarse transport regime. Using datacollected by a tracers-based monitoring carried out in a 4-km long study-sector of the ParmaRiver (Northern Apennines, Italy) located downstream from a dam representing a zerocoarse-flux boundary, we applied a virtual velocity approach for estimating the bed materialload at four river cross-sections. The virtual velocity approach represents one of the fewavailable and reliable alternatives for estimating the bed material transport in wide riverscharacterized by coarse channel-material. Monitoring was carried out over 17 months (January 2016 – May 2017) during whichnine competent events occurred, the highest one with a recurrence interval of 2.1 years. Fielddata, elaborations and estimate results provided new insights about the impacts of the damon coarse material mobility and sediment regime. A longitudinal gradient of thedam effects has been recognized along the study sector. Sections located closer tothe zero-flux boundary are characterized by more evident impacts due to deficitof coarse sediment input from upstream. Sediment dynamic is strongly altered,especially in the high armored main channel, and the overall bed material load isextremely low, ranging between 0.4*103 m3 and 1*103 m3 during the 17-monthscalculation period at 90 - 110 m wide sections. A partial recovery of sediment mobilitywas recognized at the sections located further from the dam where both partialand full transport occur at different water discharges and estimates provide highersediment yield (about 4*103 m3 during the 17-months calculation period at 120- 140 m wide sections). The presence of a zero-flux sediment boundary (i.e. thedam) was able to induce significant alterations also in terms of partial transportcontribution, relations between bed material flux and hydrological characteristics of thecompetent event and contribution of different geomorphic units to the total coarsetransport. Our results highlight the impacts that dams can induce on coarse material dynamics andsediment transport in large gravel-bed rivers, which are the primary control factors ofmorphodynamic response in terms of channel reorganization (e.g. morphology) andstreambed features alteration (e.g. grain size, structure). The new insights achieved from theselected case-study are likely to be applicable to many other rivers experiencingchannel adjustments due to the interruption of longitudinal coarse-sediment transfer. [ABSTRACT FROM AUTHOR]

The coastDat datasets were produced to give a consistent and homogeneous database mainly for assessing weather statistics and climate changes for the recent decades, e.g., in frequencies of extremes for Europe, especially in data sparse regions. The atmospheric parts of these datasets are regional climate reconstructions for the entire European continent, including the Baltic Sea and North Sea and parts of the Atlantic. The simulations were conducted with the regional climate model COSMO-CLM (CCLM). CoastDat2 (Geyer 2014) covers the period 1948-2017 with a horizontal grid size of 0.22 degree in rotated coordinates, and global reanalysis data of NCEP1 were used as forcing and for the application of spectral nudging. CoastDat3 covers the period 1979-2016 with a horizontal grid size of 0.11 degree in rotated coordinates, and global reanalysis data of ERA-Interim were used as forcing and for the application of spectral nudging.In order to also allow a consistent assessment of hydrological changes, we extended these datasets with high resolution river discharge. The discharge was simulated with the recently developed 5 Min. version of the Hydrological discharge (HD) model (Hagemann et al., submitted). Note that for the development of this HD model version, no river specific parameter adjustments were conducted so that the HD model is generally applicable for climate change studies and over ungauged catchments. In our presentation, we evaluate the simulated discharge using various metrics.ReferencesGeyer, B.: High-resolution atmospheric reconstruction for Europe 1948–2012: coastDat2, Earth Syst. Sci. Data, 6, 147-164, https://doi.org/10.5194/essd-6-147-2014, 2014. Hagemann, S., T. Stacke and H. Ho-Hagemann, High resolution discharge simulations over Europe and the Baltic Sea catchment. Frontiers in Earth Sci., submitted. [ABSTRACT FROM AUTHOR]

The highly intermittent and sparse nature of the Surface Water and Ocean Topography (SWOT) river observations in both space and time poses a major challenge to users for most applications. The locally restricted river information also hinders the realization of the mission's full value for hydrologic sciences. We tackle the challenges with a two-pronged approach:First, a river discharge interpolation scheme is developed based on the Inverse Streamflow Routing (ISR) model, which assembles the discrete discharge estimates in a river basin into a spatially complete and temporally continuous data record. Through discharge-to-runoff inversion, the ISR interpolation propagates observed discharge information exhaustively across the reachable space/time within the river basin in both upstream and downstream directions.Second, to further extend the propagation of SWOT information beyond basin boundaries and to improve gap-filling in space/time, the ISR model is updated to include spatiotemporal correlations in runoff errors. Such error correlations in runoff field, as an exponentially decayed isotropic function in space/time (beyond basins), allows us to propagate storm signals picked up by SWOT from one basin to its neighbors.Synthetic experiments are conducted over the Ohio River basin, as well as 16 global river basins. Significant and robust improvements are found in these experiments with large SWOT observation gaps much better filled and higher KGE score in interpolated discharge records. Results suggest that we can boost the utility of SWOT river products and its value for hydrologic sciences by expanding a very local/intermittent observation platform into a far-reaching source of hydrologic information through both river hydrodynamics in channel networks and spatiotemporal coherence of weather systems in the atmosphere. [ABSTRACT FROM AUTHOR]

The Yellow River (or Huanghe), with its highest sediment load in the world, provides a key link between continental erosion and sediment accumulation in the western Pacific Ocean. However, the exact age of its influence on the marginal sea is highly controversial and uncertain. Here we present high-resolution records of clay minerals and lanthanum to samarium (La/Sm) ratio spanning the past ~1 million years (Myr) from the Bohai and Yellow Seas, the potential sedimentary sinks of the Yellow River. Our results show a climate-driven shift in provenance from small, proximal mountain rivers-dominance to the Yellow River-dominance at ~880 ka, a time period consistent with the Mid-Pleistocene orbital shift from 41-kyr to 100-kyr cyclicity. We compare the age of this provenance shift with the available age data for Yellow River headwater integration into the marginal seas and suggest that the persistent influence of the Yellow River on the Chinese marginal seas must have occurred at least ~880 ka ago. This new finding is the first offshore evidence on the drainage history of Yellow River within an accurate chronology framework. [ABSTRACT FROM AUTHOR]

Every year thousand people suffer from dangerous hydrological events like floods and debris flows all over the world. The aim of this research was to calculate characteristics of these hazards such as maximum discharges of the flows, water-levels and cross-sectional areas, which are necessary for defense construction designing. The first object of our research was the river Vladimirovka, the right tributary of the river Susuya. This river is situated in Sakhalin region near Yzhno-Sakhalinsk, one of the largest cities there. Despite the fact that disastrous debris flows were observed for more than last 10 years, flash floods are much more frequent events for the territory. During the research we applied the model of unsteady water movement, which was developed in Saint Petersburg State University (Vinogradova and Nikiforovskaia, 2015). Basis of the model is the solution of an one-dimensional set of equations of Saint-Venant. For this purpose, the numerical scheme developed in Institute of Hydrodynamics from Academy of Sciences of the USSR (IH) was used. The calculations were carried out with different probability of flows like 10, 1 and 0.1 percent. Due to the fact that there is no calibration block in the model and code of roughness is a functionally dependent parameter, we conducted several numerical experiments to clarify maximum values. For estimation parameters of flood, we chose the Porus river, located in Novgorod region, in which a disastrous event occurred in April 2017. Special field measurements such as hydraulics-morphometric were carried out by LLC "NPO" Gidrotekhproekt "in 2017 according to a design specification. To sum up, this research provided characteristics of floods and debris flows, which could be used for protection of the territory. [ABSTRACT FROM AUTHOR]

The formosan land-locked salmon is one of the representative but endangered species in Taiwan and the first-order stream of Yushen Creek in Chichiawan Watershed, Taiwan is the major habitat for the salmons. Unfortunately, the intensive water exchanges beneath the streambed caused the creek to cease flow, and the fragmented creek could not provide a sustainable environment for the rehabilitation and the population of salmon was significantly reduced. To comprehensively understand the mechanisms of surface water and groundwater interaction and mitigate the effect of fragmentation on the salmon habitat, the tracer tests and numerical models were conducted to characteristic hyporheic flux exchanges beneath the stream. Seven observation wells and seven piezometers along the stream were installed to provide long-term water levels, temperatures, and electrical conductivities of surface water and groundwater. Five tracer tests from April, 2017 to May, 2018 were conducted at different sections of reach to delineate the horizontal and vertical hyporheic flow paths and seepage flow directions through the breakthrough curves. OTIS and VS2DT were selected to simulate the concentration variations in the stream and streambed, respectively and quantify the hydraulic characteristics of hyporheic zone. The estimated storage zones and exchange coefficients by the OTIS model were used to mimic the hyporheic cells and fed into the VS2DT model to identify the hyporheic and seepage flows. The simulated results revealed that the first-order stream has frequent flux exchanges beneath a high porosity gravel streambed but this intensive interaction reduces with the existence of confluences and the high level of baseflow. The results also demonstrated the effect of topography on the flow path that water flows out of the upstream wetted channel and back into downstream wetted channel to avoid the areas of step-riffle. Finally, the hydraulic characteristics of streambed, streamflow, and morphology of stream should be considered to mitigate the fragmentation when conducting the river restoration of the first-order stream in the alpine watershed. [ABSTRACT FROM AUTHOR]

This work provides new insights on the use of a combined multidisciplinary approach forestimating trend and rates of valley incision in tectonically active mountainouslandscape. To this aim, here we present the results of a combined analysis includingstream terraces investigation, longitudinal profiles modelling and time-dependent,catchment-scale, geomorphometry obtained in the headwater sector of the Tronto River basin,located in the southern epicentral area of the 2016-2017 seismic sequence of CentralItaly.The most relevant tectonic structures in the area are the Mt. Gorzano fault (south-easternsector), the Sibillini Mts thrust (western sector) and the southern tip of the active Vettorefault, ie the seismogenic structure responsible for the 2016 mainshock. Geomorphometric analysis and stream long-profiles modelling were performed using a 5m-gridded DTM obtained starting from the altimetric dataset included in the 1:5,000topographic maps available for the whole study area in vector format. Time-dependentcatchment-scale R∕Sr metrics and long-profile indices (SL and χ) were computedrespectively using the hydrological tool in ESRI® ArcGIS and the TopoToolboxworking in Matlab®. Stream terraces dataset derives from field survey, integrated withthe visual inspection of a DTM-derived hillshade map and aerial/satellite imageryinterpretations. The combination of R∕Sr time-dependent metrics and stream terraces analysis allows toinfer the timing of the base level changes during upper Quaternary and the long-profilesmodelling provided interesting results for better comprehending the effects of these changeson the fluvial system. The analysis here performed provided new data useful for betterunderstanding the trend and rates of the valley deepening in the headwater sector of theTronto River, to reconstruct basin-scale modifications such as stream captures and, more ingeneral, resulted useful for better comprehending the morphoevolution of this tectonicallyactive key area of the Apennines. Nonetheless, our study did not allow to unravel therole exerted by the single active tectonic structures in the present and past fluvialmorphodynamics, because of the superimposed effects of large gravitational rock slopefailures on the spatial pattern of long-profiles anomalies and local base level variations. [ABSTRACT FROM AUTHOR]

Since the antiquity, three main hypotheses have been proposed in Greek and Roman literature to explain the now well-known terrestrial part of the water cycle. Such hypotheses have been formulated by Anaxagore (500-428 BC), as reported by Aristote, then Lucrèce (98-55 BC): the water cycle is due to the combination of precipitation and evapotranspiration. Despite some measurements have been conducted during the medieval period, the water cycle has been fully demonstrated only at the Renaissance. Perrault (1664) has proposed an estimation of the annual budget of the Seine River in Paris, showing that the annual flow can be estimated using the precipitation on the corresponding catchment. This history has been largely reported by different authors (Dooge, 1959; L'Hôte, 1990; Chow, 1964, 1988). What is not so well-know is that this demonstration has been done despite huge errors on precipitation and annual discharge which have compensated one another so that the calculated ratios of the output/input are very similar now than those calculated by that time. All the details on these estimations will be provided. This story illustrates that: 1) budget are powerful tools and could always be useful to identify sources and compartments for multiple elements, at various temporal and spatial scales, in relation with global changes; 2) the formulation of clear hypotheses have to come before measurements and could take time to be fully demonstrated. [ABSTRACT FROM AUTHOR]

We present an inverse method enabling to estimate the discharge and an effective bathymetry of rivers observed by altimetry only, in particular from the forthcoming SWOT mission (NASA-CNES et al., 2021). First an original reading of the inverse problem is proposed in terms of wave propagations through "identifiability maps". Next dedicated low complexity systems are derived to obtain simple (algebraic) relations between the three critical flows unknowns: the discharge Q(x,t), an effective bathymetry b(x) and the corresponding friction parameter (Manning-Strickler) K(x;h) (h the water depth). Next an advanced Variational Data Assimilation (VDA) formulation based on the complete physics (Saint-Venant's equations) is elaborated. The resulting Hierarchical Variational Discharge Inference (HiVDI) algorithm turns out to be robust and relatively accurate passed the assimilation of a hydrological cycle (~ 1 year variations, considered as a "learning period"). Next, given the identified parameters (b(x), K(h)) during this "learning period", the low complexity systems enable to estimate Q(x,t) in real-time.Numerical results on numerous river datasets are analysed in detail; SWOT-like measurements may be provided by the instrument simulator. References [1] P. Brisset, J. Monnier, P.-A. Garambois, H. Roux. "On the assimilation of altimetry data in 1D Saint-Venant river models". Adv. Water Ress. (2018). [2] K. Larnier, J. Monnier, P.-A. Garambois, J. Verley. "On the estimation of river discharges from altimetry". Revised version in oct. 18, should appear soon. [3] "DassFlow: Data Assimilation for Free Surface Flows", open-source computational software. Mathematics Institute of Toulouse, INSA, CNRS, CNES, CS corp. http://www.math.univ-toulouse.fr/DassFlow [ABSTRACT FROM AUTHOR]

The morphology and dynamics of the 1500 km-long Guianas coast, South America, are strongly influenced by mud supplied by the Amazon River. A fraction of this mud (20% of nearly 1 billion tons annually) is organized into large banks that migrate along the coast under the influence of waves and currents, separated by 'inter-bank' zones. 'Bank' zones significantly dissipate the wave energy transmitted shoreward, whereas inter-bank zones are commonly characterized by a relatively mud-free shoreface, and wave energy is thus more efficiently transmitted to the shore. The alongshore alternation of shifting bank and inter-bank zones is strongly modulated by water discharge from the local rivers, which depends essentially on catchment size. The hydrology and sediment fluxes of many of these rivers, which drain the crystalline rocks of the Guiana Shield between the Amazon and the Orinoco River deltas, are still largely unknown. Even the catchment size of several of these rivers is not known with certainty. The relationship between discharge from these Guiana Shield rivers and the Amazon mud-bank belts results in a variety of estuarine morphological and dynamic configurations. Further estuarine diversity is engendered by lithology. A preliminary classification of 15 estuaries, based on plan morphology and ongoing analyses of estuarine hydrodynamics, suggests four basic types: (1) estuaries fixed by headlands of Precambrian basement rocks (Mahury, Cayenne, and Kourou Rivers); these are associated with small catchments and found only in French Guiana, where the basement crops out along the coast; (2) estuaries with mouths diverted westward (the direction of regional alongshore sediment transport) by prograded mud capes and spits, reflecting a significant influence of multi-decadal to multi-millennial coastal accretion of Amazon-derived mud (Cassipore, Uaça, Rivers in Amapa, Brazil; Oyapock between Brazil and French Guyana; Approuague, Sinnamary and Mana Rivers in French Guyana; Suriname and Coppename Rivers in Suriname; Berbice River in Guyana); (3) estuaries oriented normal to the coast and associated with relatively large-discharge rivers (Maroni River between French Guiana and Suriname; Corentyne River between Suriname and Guyana; (4) a prograded estuary mouth with a transitional morphology towards a delta (Essequibo River in Guyana, the largest river on the Guianas coast after the Amazon and the Orinoco). On-going monitoring of the sediment fluxes and hydrodynamics of a type 1 (Mahury) and a type 3 estuary (Maroni), both of which are fixed (lithologically for type 1, and hydrodynamically for type 3), and akin, morphologically, to normal trumpet- or funnel-shaped estuaries, shows a tropical seasonal regime but which is strongly influenced by Amazon mud during the low-discharge dry season. This mud influence from the distant Amazon constitutes a unique aspect of the river mouths on the Guianas coast. [ABSTRACT FROM AUTHOR]

There is limited information describing the influence of site characteristics on post-construction conditions and effectiveness of check dams at the watershed scale. In particular, it is important to achieve a better understanding of some geomorphological and vegetation factors (such as check dam geometry, channel morphology and vegetation cover) on sediment retention capacity and structure functioning. To address these issues, a combination of multivariate statistical techniques were applied to the most important characteristics of 273 check dams installed 3-5 years ago in a Mexican large watershed. This quantitative analysis showed that the failure of check dams was associated with low vegetation cover of the drained sub-watersheds; conversely, with a well developed vegetation cover the majority of check dams were functional or filled, in both cases not broken. Taller structures were most likely to be exposed to failure risk, while check dams with lower height, but with well-developed sediment wedges and large vegetation cover, were more stable. Finally, upstream height of check dams and vegetation cover of the drained sub-watersheds were factors with a considerable influence on sediment retention processes acting behind the stone structures. Overall, this study has provided a quantitative evaluation of the dominant factors influencing the post-construction conditions of check dams and their ability to store sediment, and thus provides land managers insights into the best strategies for soil conservation at the watershed scale using check dams. These findings suggest that managers: (i) consider with caution the installation of control works (such as stone or rock check dams) in sub-watershed with low vegetation cover and highly erodible soils, since here the high sediment transfer rates may increase the structure failure likelihood; (ii) adopt a larger number of small structures rather than controlling the evolution of the channel longitudinal profile by large-sized check dams, since taller structures are most likely to be exposed to failure risk, thus loosing much of their functioning. [ABSTRACT FROM AUTHOR]

Areas located at plate boundaries are characterized by the presence of seismic, volcanic, and geothermal activity, as well as ore deposition. Such processes are enhanced by the circulation of hydrothermal fluids in the crust transporting volatiles from either the deep crust or the mantle to the surface. Intense geodynamic activity is also taking place in Greece giving rise to: (i) the highest seismicity in Europe, (ii) the presence of an active volcanic arc and numerous areas of anomalously high geothermal gradient, and (iii) a widespread occurrence of thermal springs.Elevated heat flow values are concentrated in Sperchios basin, an area characterised by a system of deeply rooted extensional faults and quaternary volcanic activity. This regime favoured the formation of hydrothermal systems, the surface expression of which are thermal springs with intense bubbling of CO2-rich gases. Flux measurements in the bubbling pools were made with the floating chamber method. The highest bubbling CO2 output is found in Thermopyles and Psoroneria (1 and 2 t/d, respectively). The outgoing channels of these springs have an elevated flow (>250 l/s) of gas-charged water (>15 mmol/l of CO2). Although no bubbling is noticed along the stream, the CO2 content decreases by an order of magnitude after few hundreds of metres, indicating an intense degassing from the water. Taking into account the water flow and the amount of CO2 lost to the atmosphere, the CO2 output of the outgoing channels is quantified in >10 t/d for Thermopyles and ~9 t/d for Psoroneria. An estimation is also made at Ypati, Kamena Vourla, Koniavitis and Edipsos, where the mean values reach 1 t/d of CO2 for each spring. The obtained values are always higher respect to the estimated outputs from visible bubbling, suggesting that most of the degassing is "hidden". Furthermore, the loss of CO2 from the water determines a shift in dissolved carbonate species as demonstrated by the pH increase along the channel that leads eventually to an oversaturation in carbonate minerals and therefore travertine deposition.To sum up, the total CO2 output of the study area is estimated at ~30 t/d, with the major contribution deriving from the degassing along the outflow channels of the thermal springs. Such output is comparable to that of the single active volcanic systems along the South Aegean Volcanic Arc (Sousaki, Methana, Milos, Santorini, Kos and Nisyros) and highlights the importance of "hidden" degassing along CO2-oversaturated streams. [ABSTRACT FROM AUTHOR]

During the last decades several low flow periods, at European level, occurred with severe impacts not only on the river itself but also on the civil society. Low flow periods affect navigation, hydropower production and the environment. A hot, dry 2018 summer has left the central European rivers and lakes at record low water levels, causing chaos for the inland shipping industry, environmental damage and billions of euros (dollars) in losses. Similar to floods, low flows are natural events which can considerably restrict different uses and functions of the river and impact water quality and the aquatic ecosystem. Moreover, it is expected that climate change will to lead to drier summers in Western Europe and therefore possibly to more frequent and more severe low flows in rivers in the future. The results presented here show that the summer 2018 low flow situation, over the Rhine river, could have been predicted one season ahead using previous months sea surface temperature, sea level pressure, precipitation, mean air temperature and soil moisture. Moreover, the statistical model was able to predict more than 85% of the water levels for August 2018 one month ahead. The lagged relationship between the monthly and/or seasonal streamflow and the climatic and/or oceanic variables vary between 1 month (e.g. local precipitation, temperature, and soil moisture) up to 6 months (e.g. sea surface temperature). Given that all predictors used in the model are available at the end of each month, the forecast scheme can be used to predict extreme events and to provide early warnings for upcoming low flow periods. [ABSTRACT FROM AUTHOR]

In industrialized countries, the assessment of water quality in rivers remains a timely topic. Especially hydrophobic organic pollutants that typically sorb to suspended sediments (e.g., PAH), and pharmaceuticals that are not completely removed by regular treatment in wastewater treatment plants (WWTP) have raised environmental concerns. These pollutants occur at concentrations of nano- to micrograms per liter in rivers. Continuous monitoring of these compounds is time- and cost-consuming. Thus we developed a particle-facilitated pollutant transport model and a reactive solute transport model with transient storage to understand the environmental processes that determine the fate of micropollutants in river systems. We applied the models to two small exemplary rivers, the Ammer and Steinlach River in southwest Germany. While the Ammer River is mainly fed by groundwater, the river Steinlach is substantially impacted by WWTP effluent. Results show that the supply and composition of sediments determine to a large extent the PAH load. At the river Ammer, the high contribution of urban particles with high PAH content results in the dominant contribution of PAHs from urban areas to the annual PAH load. Since the flow rate and river geometry determine the deposition and remobilization of sediments in the river, they control the in-stream redistribution of PAHs. In steep reaches, sediment turnover governs the turnover of PAH, whereas in very mild river segments diffusion of PAH from the river bed to the mobile water is relevant and reduces PAH turnover times. The simulated PAH legacy occurs in river segments with slow sediment turnover and may have remained 10-20 years after the environmental regulation in 1970s in the Ammer River. For the river Steinlach, transient storage plays a significant role for flow and solute transport, especially under low-flow conditions. The increase of the transient storage ratio increases the travel time and thus affects solute transport. Degradation processes of pharmaceuticals are affected by local conditions, e.g. pollutant transformation decreases with increasing flow rates. This influence is especially significant for pollutants that undergo biodegradation only. Overall, our study provides a framework to investigate the long-term fate of sediment-bound micropollutants (PAH) and the transport and transformation dynamics of dissolved micropollutants (pharmaceuticals). The framework is transferable to other small streams that are affected by anthropogenic micropollutants. [ABSTRACT FROM AUTHOR]

Fluvial systems (streams and rivers) are globally suggested to dominate the inland water CO2 source to the atmosphere. However, this estimate relies on a number of assumptions and the data scarcity makes the estimate highly uncertain. One of the critical knowledge gaps is the lack of directly sampled and temporally resolved data from agriculture dominated areas. Agriculture land is heavily managed by humans (drainage, nutrient addition, soil cultivation etc.), while magnitude and dynamics of stream CO2 are likely very different compared to areas of other land-use (e.g. forest and wetland). Here we present high-frequency stream CO2 concentration data collected from a Swedish agricultural headwater catchment covering more than a year of open water including periods of snowmelt, drought as well as rain storms. The stream displayed high but at the same time very variable CO2 concentrations (median = 3.4 mg C L-1, IQR = 3.3 mg C L-1). The high dynamics were both controlled by the rapid hydrological response to precipitation but also to high biological activity causing diel cycles in CO2 with amplitudes of < 3.2 mg C L-1. Also, rain storm events following periods of drought caused elevated stream CO2 concentrations. The high diel dynamics and the short-term events would have been missed with standard snapshot sampling. Furthermore, the stable isotopic composition of the DIC pool suggests a mixture of geogenic and biogenic inorganic C sources indicating that geogenic C might be used in primary production. The study highlight the need for further studies of stream CO2 in agricultural areas and where high-frequency measurements will be a requirement for capturing the dynamics. [ABSTRACT FROM AUTHOR]

Soil erosion by water is one of the most important factors affecting contemporary landscape changes within the lowland geoecosystems in Central Europe. Soil erosion mainly depends on: rainfalls (especially its intensity and erosivity), length of slope and its inclination, type of cultivation and usage of land, anti-erosion treatments and susceptibility of soils to erosion. The main goal of the research was related to evaluate rainfall impact on soil erosion processes. The research was conveyed by stationery observation and quantitative researches that have been conducting within the Chwalimski Brook catchment (NW Poland) since the early 90s and by computation rainfall characteristics: intensity, kinetic energy and erosivity (rainfall erosivity index EI30).Presented results contains data of runoff, soil loss and rainfall collected at testing plot in a 16-years period (2001-2016 hydrological years). The slope with the test area is located within the 1st order catchment being a subsystem of the Młyński Brook catchment and then followed by the upper Parsęta catchment. The slope is covered with gleyic retisols and maintained with no vegetation as a black fallow. Its average inclination is about 4 degrees with its south-east exposure. The measuring system of soil erosion covers a testing plot (42 meters long, 4 meters width). The annual rainfall erosivity changed from 144.7 to 782.1 MJmm/ha/h, precipitation sums from 524.9 to 919.7 and soil loss varied from 0.074 to 4.471 kg/m2. The greatest rates of soil loss were established in the most rainy years. However some significant annual soil loss (e.g. in 2013 and 2014) occurred in below average rainfall totals. Therefore, the achieved results show that annual soil erosion primarily depends on individual rainfall and erosive events. Hence, magnitude of soil erosion cannot be estimated only on the basis of rainfall totals, but it is also necessary to consider intensity and erosivity of single rainfall events. [ABSTRACT FROM AUTHOR]