Stretch Of River Research Articles

The community-centered freshwater biogeochemistry model unified RIVE v1.0: a unified version for water column

Abstract. Research on mechanisms of organic matter degradation, bacterial activities, phytoplankton dynamics, and other processes has led to the development of numerous sophisticated water quality models. The earliest model, dating back to 1925, was based on first-order kinetics for organic matter degradation. The community-centered freshwater biogeochemistry model RIVE was initially developed in 1994 and has subsequently been integrated into several software programs such as Seneque-Riverstrahler, pyNuts-Riverstrahler, ProSe/ProSe-PA, and Barman. After 30 years of research, the use of different programming languages including QBasic, Visual Basic, Fortran, ANSI C, and Python, as well as parallel evolution and the addition of new formalisms, raises questions about their comparability. This paper presents a unified version of the RIVE model for the water column, including formalisms for bacterial communities (heterotrophic and nitrifying), primary producers, zooplankton, nutrients, inorganic carbon, and dissolved oxygen cycles. The unified RIVE model is open-source and implemented in Python 3 to create pyRIVE 1.0 and in ANSI C to create C-RIVE 0.32. The organic matter degradation module is validated by simulating batch experiments. The comparability of the pyRIVE 1.0 and C-RIVE 0.32 software is verified by modeling a river stretch case study. The case study considers the full biogeochemical cycles (microorganisms, nutrients, carbon, and oxygen) in the water column, as well as the effects of light and water temperature. The results show that the simulated concentrations of all state variables, including microorganisms and chemical species, are very similar for pyRIVE 1.0 and C-RIVE 0.32. This open-source project highly encourages contributions from the freshwater biogeochemistry community to further advance the project and achieve common objectives.

Population changes in Gharial (Gavialis gangeticus) vary spatially in Chitwan National Park, Nepal

Gharials, large crocodilians found only in South Asia, are widely seen as a flagship species for river conservationin Nepal, especially in Chitwan National Park, where a headstart program has supplemented the populationsince 1981. The population has shown signs of recovery only in the last decade, so continued monitoring of populationtrends is vital for conservation. We conducted annual winter population surveys for gharial in Chitwan between 2017and 2022, during which we also characterized riverbank substrate availability and basking preferences. We documentedpotential threats to the species in Chitwan throughout the year. Overall, we counted an increasing number of Gharialsin Chitwan; however mixed-effects modelling of Gharial encounter rate showed that increasing encounters rates are notevenly distributed throughout available habitat, with some river stretches having stable or decreasing trends. Encounterrates on the Rapti River increased in all transects, compared to more variable results on the Narayani River, likelyattributable to higher levels of human disturbance and the impact of captivity on habitat selection. Fewer Gharials wereseen in transects with high levels of disturbance due to sand mining and the extraction of river substrates, highlightingthis threat as a major concern. Regular reports of bycatch in illegal gillnets was the major observed source of mortality.A lack of an increasing population trend in the stretch above a large barrage suggests that recruitment is minimal inthis area, and the dam likely has a negative impact on upstream Gharial recruitment. We cautiously suggest that theChitwan population is recovering, but that recovery is hampered by threats, especially substrate extraction, illegal gillnetfishing, and river fragmentation by a dam.

Parasitos de peixes de um rio costeiro neotropical dentro de um hotspot de biodiversidade

Abstract: Aim We investigated the ichthyofauna parasite component community across a gradient of anthropogenic pressures of the Guaraguaçu River, south Brazil, a Neotropical river of central importance for biodiversity conservation. Methods After fish sampling, all fish were identified, measured, weighed and eviscerated. The viscera and gills were inspected for parasite screening and subsequent identification. Parasite diversity estimators were calculated for the most abundant host species. Results A total of 159 host specimens from 12 species were examined, being 140 (88.05%) found to be infected with at least one parasite, including 14 new parasite occurrences. The most widely distributed parasite was the nematode Contracaecum sp., found in 8 host species. The highest mean infection intensity and mean abundance was observed for the monogenean Aphanoblastella mastigatus, infecting the Silver catfish Rhamdia quelen. The Shannon-Wiener, Jost and Simpson indexes were higher for the more abundant fishes, except for the Trahira Hoplias malabaricus. Most host species harbored parasites in poorly aggregated distribution, according to the discrepancy index. The Berger-Parker index showed monogenean dominance in all hosts except for H. malabaricus. We found little evidence for parasite infracommunity changes across the gradient of the river. Conclusions We described the infection patterns in an important Neotropical river. The new parasite occurrences highlight the contribution of our study. Fish-parasite interactions changed throughout the river stretches, and we argue that it does not necessarily means changes in diversity and abundance of parasite within species, but the rearrange of interactions. Moreover, it seems that parasites are more abundant in most impacted sites, another reason to continue the monitoring.

Altitudinal distribution and body condition of migratory fish juveniles Megaleporinus obtusidens (Valenciennes) and Salminus brasiliensis (Cuvier) in the main channel of the Uruguay River, Southern Brazil.

In this study, we analyzed the altitudinal distribution and body condition of the juvenile migratory fish Megaleporinus obtusidens and Salminus brasiliensis in the Uruguay River, a South American subtropical river. We used the presence/absence data and condition factor (K) of juveniles as indicators to try to characterize some recruitment patterns of migratory fish in the main channel of the Uruguay River. Gillnet sampling was conducted during two reproductive years, 2015-2016 and 2016-2017 (November and March of each reproductive year), in three Uruguay River stretches at different levels of altitude. The nets remained in the water for 10-12 hours per night or day for 10 days during each field trip (NOV-15, MAR-16, NOV-16, and MAR-17). The abundance of M. obtusidens juveniles were similar between the two reproductive years, whereas S. brasiliensis capture was higher during the 2015-2016 reproductive year. The probability of finding M. obtusidens juveniles in the Uruguay River was negatively correlated (p < 0.05) with the altitudinal gradient of the sampling points, as shown by the GLM model. For S. brasiliensis, the logit model indicated a non-significant probabilistic relationship (p > 0.05) between the presence of juveniles of this fish species and the altitude gradient. Regarding the body condition of juveniles, the water quality of the sampling points did not affect the juvenile condition factor for either species; however, a positive relationship (p < 0.05) was found with the water level for both species, even with an adjusted R2 of 0.13 for M. obtusidens and 0.48 to S. brasiliensis. Altitude gradient and water level were factors that may affect the juvenile distribution and body condition of these species, respectively, in the Uruguay River. Therefore, this information can be used in hydropower generation policies to conserve migratory fish populations in the Uruguay River Basin.

The ichthyofauna of the upper Neretva River

Fish were sampled at nine locations of the upper Neretva River, upstream of Glavatičevo. Evidence of the endangered softmouth trout (Salmo obtusirostris) was obtained as well as the presence of other native and non-native salmonids. Genetic analysis suggests that the native brown trout (Salmo trutta) in the upper Neretva is homogeneous with no significant introgression by introduced Atlantic-lineage brown trout and quantitative catch data show that their populations are healthy with densities above 1,000 ind/ha. However, the relatively low biomass estimates may be the result of overharvesting. A new haplotype of the mitochondrial control region of the bullhead (Cottus gobio) was detected and confirmation of native S. trutta, Barbatula barbatula, Phoxinus sp., and C. gobio in the upper reaches, underlining the importance of this river stretch. The planned expansion of hydropower plants in the upper Neretva and its tributaries will have a significant negative impact on the largely untouched ichthyofauna, as is clearly demonstrated by the conditions found in the middle course of the river, which has been dedicated to hydropower production.

Condition-dependent survival and movement behavior in an endangered endemic damselfly

Movement is essential for the maintenance of populations in their natural habitats, particularly for threatened species living in fluctuating environments. Empirical evidence suggests that the probability and distance of movement in territorial species are context-dependent, often depending on population density and sex. Here, we investigate the movement behavior of the spring cohort of an endangered endemic damselfly Calopteryx exul in a lotic habitat of Northeast Algeria using capture-mark-recapture (CMR) of adults. By sampling 10 gridded river stretches across a 2 km section of the watercourse, we were able to estimate the distance of movement throughout individual lifespans and estimate movement probability for both males and females. We used multistate models to examine whether individual density and sex ratio influence survival and movement probability. We found that males and females had similar movement kernels with most individuals moving short distances (83% performing movements of < 100 m and only 1% > 1000 m). Of the 547 marked individuals, 63% were residents, and 37% were movers (moved at least 50 m from one sampling occasion to another). Survival probability showed higher estimates for females and was slightly density-dependent (i.e., lower survival probabilities were associated with high male densities). Survival probability did not show a marked difference between residents and movers. Movement probability and distances were positively correlated with individual density, but were not or slightly correlated with sex ratio, respectively. These results are not in line with the hypotheses of sex-biased movement and survival costs of movement. Our results suggest that the species performs mostly short-distance movements that are dependent on intraspecific interactions.

ANALISIS KUALITAS AIR SUNGAI BALANGAN DI KABUPATEN BALANGAN BERDASARKAN PARAMETER FISIK DAN KIMIA (LOGAM TERLARUT)

The Balangan River stretches and flows in the Balangan Regency area. Balangan River length is 30 Km, has a width of about 50 m wide and average depth of 3.5 m. The Balangan River flows through 8 districts (Paringin District, Paringin Selatan District, Lampihong District, Batumandi District, Awayan District, Tebing Tinggi District, Juai District and Halong District). The Balangan River is used by the local community as a source of clean water for household needs (bath wash toilet), agriculture and farming. Further and more specific research on the water quality of the Balangan River is urgently needed to obtain information regarding the status of water quality, water quality status and obtain pollutant load information as well as to be evaluated so that it can be used as a recommendation for efforts to reduce pollutant loads so that the target of improving water quality is well achieved by the community and local government. This study aims to identify the water quality of the Balangan River based on physical and chemical parameters. Data collection was carried out in the measurement range of the first quarter of 2015 to the third quarter of 2022 by taking river water samples every quarter. Sampling points and inspection of the insitu water quality of the Balangan River were carried out at two locations in the upstream and downstream. The surface water sampling method used is in accordance with SNI 6989.57:2008. During the measurement period in the Balangan River, physical and chemical parameters that did not meet the quality standards required in Government Regulation no. 22 of 2021 attachment VI (Class 1) are Total Suspended Solid (TSS), Iron (Fe) and Zinc (Zn).

Physicochemical and Microbial Quality of Water from the Ugandan Stretch of the Kagera Transboundary River

Increasing global pollution of water resources undermines the efforts invested in the realisation of Sustainable Development Goals. In developing countries, for example, water pollution is exacerbated by poor regulatory structures and improper waste disposal. This study, for the first time, investigated the physicochemical and microbial parameters of surface water from the Ugandan stretch of the Kagera transboundary river. Surface water (n = 135) from downstream, midstream and upstream of the river was sampled between February 2021 and June 2021, and analysed following standard methods for the examination of water and wastewater. Further, the samples were analysed using flame atomic absorption spectroscopy for the presence of heavy metals: nickel, lead, chromium, cadmium and copper. The obtained results showed that turbidity (24.77 ± 5.5–43.99 ± 6.87 mg/L), colour (118 ± 8.90–145.2 ± 30.58 Pt-co units), Escherichia coli (4.96 ± 7.01 CFU/100 mL), lead (23.0 ± 11.0–43.0 ± 12.0 µg/L) and cadmium (3.3 ± 1.0–10.1 ± 10.0 µg/L) were at levels that surpassed their permissible limits as per World Health Organization guidelines for potable water. These results are lower than previously reported for the Rwandese stretch of this river, but still present potential health risks to the population whose livelihoods depend on the river. Measures should therefore be instituted by the East African Community member states to mitigate riverine pollution and ensure sustainable use of the Kagera transboundary river.

Possible Effects of Changes in Carbonate Concentration and River Flow Rate on Photochemical Reactions in Temperate Aquatic Environments.

In temperate environments, climate change could affect water pH by inducing enhanced dissolution of CaSO4 followed by biological sulphate reduction, with the potential to basify water due to H+ consumption. At the same time, increased atmospheric CO2 could enhance weathering of carbonate rocks (e.g., dolomite) and increase the total concentration of dissolved carbonate species. Both processes enhance phototransformation by the carbonate radical (CO3•-), as shown for the non-steroidal anti-inflammatory drug paracetamol, provided that the dissolved organic carbon of water does not undergo important fluctuations. Climate change could also affect hydrology, and prolonged drought periods might considerably decrease flow rates in rivers. This is a substantial problem because wastewater pollutants become less diluted and, as a result, can exert more harmful effects due to increased concentrations. At the same time, in low-flow conditions, water is also shallower and its flow velocity is decreased. Photochemical reactions become faster because shallow water is efficiently illuminated by sunlight, and they also have more time to occur because water takes longer to cover the same river stretch. As a result, photodegradation of contaminants is enhanced, which offsets lower dilution but only at a sufficient distance from the wastewater outlet; this is because photoreactions need time (which translates into space for a flowing river) to attenuate pollution.

Mapping and assessment of river water quality under varying hydro-climatic and pollution scenarios by integrating QUAL2K, GEFC, and GIS

Water quality modelling has proved to be effective method for managing river water quality. But the most effective and comprehensive approach involving integration of river water quality simulation and pollution visualization with the objective of pollution reduction and maintenance of environmental flow strategies has gained less attention. Thus, the objective of this study was to employ an integrated approach for mapping and analysing river water quality under various hydro-climatic and pollution scenarios. Specifically, this approach involved the integration of a river water quality simulation model, QUAL2K, Global Environmental Flow Calculator (GEFC), and Geographical Information System (GIS) to develop water quality index (WQI) based map charts of water quality. The calibrated QUAL2K model was utilized to simulate WQI parameters including water temperature, pH, electrical conductivity, dissolved oxygen (DO), biological oxygen demand (BOD), nitrates (NO3), ammonia (NH4), and alkalinity. To analyse the WQI, the Weighted Arithmetic-Water Quality Index (WA-WQI) method was employed for various individual and combined pollution scenarios, environmental flow (Eflow), and climate change scenarios. The developed integrated approach was applied to the Bhadravati segment of Bhadra River, India. The findings revealed that the prevailing WQI status of the study stretch ranged from poor to unsuitable for drinking purposes. This deterioration can be attributed to the impact of both industrial and municipal effluents. By maintaining the effective Environmental Management Class (EMC) flow rates (class C flowrate of EMC (40.32 m3/s)) in conjunction with appropriate Pollution Reduction (PR) level (10% PR) at headwater and incoming drains, the stream self-purification capacity was enhanced resulting in the Bhadravati River stretch water quality transitioning to favourable water quality condition.

СТРУКТУРА МИКРОПЛАНКТОНА В ВОДЕ р. ВОЛГА НА УЧАСТКЕ с. ПРИЛУКИ – пгт КРАСНЫЙ ПРОФИНТЕРН (ЯРОСЛАВСКАЯ ОБЛАСТЬ)

In August 2021, in the channel part of the Volga River, within the river stretch between Priluki village and Krasnyi Profintern townlet, studies of bacterio- and mycoplankton have been carried out. The study was conducted at 25 stations.The quantitative structure of communities of heterotrophic microorganisms is presented by individual stations and by groups of stations identified by the type of anthropogenic load: “across from a settlement”, “lower border of a settlement”, “5 km downstream from a settlement”, “10 km downstream from a settlement”, “water intake”. The water quality was assessed. Saprophytic bacteria were isolated by the pour-plate method, the total number of bacteria and fungal propagules was determined by direct counting using an epifluorescence microscope. The total number of bacteria at the stations ranged 98.65–99.97% (on average 98.63%) and exceeded the fungi number by 73.0–3824.4 times (on average 1177.8 times). The bacterial biomass amounted to 90.0–99.86% (on average 98.63%) and exceeded the fungal one by 9.0–663.8 times (on average 168 times). In the structure of mycobiota, the mycelium biomass ranged 46.56–96.82% (on average 62.06%), which indicates the functional activity of fungi. Cluster analysis of the quantitative structure of microbial communities, for individual stations, revealed their high similarity: the values of the Bray-Curtis coefficients for number ranged 74.49–99.21%; for biomass – 71.03–98.34%. Cluster analysis of microbial communities by station groups also revealed their significant similarity: in number – 86.6–98.3%; in biomass – 88.20–98.87%. For groups of stations, a high correlation was found between the biomass of bacteria and fungi – –0.85, which indicates different environmental conditions favorable for the development of these microorganisms. The water quality in the station groups was appraised as transitional from polluted to dirty waters, from β-mesosaprobic to polysaprobic, and in trophicity, from mesotrophic to eutrophic.

Antimicrobial Resistance of Heterotrophic Bacteria and Enterobacteriaceae Inhabiting an Anthropogenic-Affected River Stretch in Bulgaria

The increasing antimicrobial resistance (AMR) of pathogens is a significant threat to human and animal health, but it is also an environmental challenge for water resources. The present study aimed to quantify heterotrophic bacteria resistant to five groups of antibiotics (ABs) in a selected Yantra River stretch (including its tributary, the Belitsa River); to assess AMR prevalence among Enterobacteriaceae; and to assess the impact of urban effluents or rural runoff on AMR prevalence along the river course at eight sampling points. Culture-dependent methods were used in a population-based study of total AMR and for AB susceptibility testing of Enterobacteriaceae isolates. The data reveal significant differences in AMR dissemination and a lower (up to 10%) proportion of different types of antibiotic-resistant bacteria (ARB) in the Yantra River water compared to the Belitsa River (up to 20%). The incidence of resistant Enterobacteriaceae isolates was in the range of 1% to gentamicin to 36% to ampicillin, including multidrug resistance of 19%, and different AMR patterns of isolates from each river. The prevalence of AMR among aquatic bacteria highlights the need for adequate waste water treatment and for management, monitoring and control of treatment processes to limit anthropogenic pressure through discharge of untreated or incompletely treated waste water and to ensure the ecological well-being of receiving waters.

Assessment of inundation risk at Bhavani River (stretch from Sathyamangalam to Velliyampalayam) using HEC-RAS

Floods are natural disasters that cause losses and damages to lives, properties and the nature. The main objective of this study is to perform hydraulic analysis using HEC-RAS and to suggest measures to mitigate flood. The study area chosen for analysis is Vellayampalayam to Sathyamangalam stretch which is located along the Bhavani river. These areas are frequently affected due to flood. Field survey is carried out to determine cross section data (width, depth, elevation of the river stretch). Discharge is calculated using rational method. These data are feed as input into HEC-RAS model for simulation. From the results, it was found that the areas around the stretch chosen as study area are greatly affected by the floods. As per field condition, the channel improvement plans were suggested to mitigate the effects of flood.

Modelling Climate Change and Water Quality in the Canadian Prairies Using Loosely Coupled WASP and CE-QUAL-W2

The prairie waterbodies face a future of warming temperatures and growing water demands. There are increasing concerns about how water quality will be affected. Water quality models are an effective tool for examining scenarios of future conditions that cannot be measured directly. This study combined WASP and CE-QUAL-W2 to investigate the potential impacts of changing flow management and climate change in the Canadian Prairies. The two models were loosely coupled to simulate a strategically managed river-reservoir network. Climate data from the Coupled Model Intercomparison Project Phase 6 (CMIP6) model ensemble were used to create future climate scenarios. Interbasin water transfers were then simulated through the coupled models to determine if any negative impacts from climate change on water quality could be offset through flow management. Climate change impacts in the river stretch were minimised due to the rapid flow travel time along the channel. The interbasin water transfers had a greater influence on water quality concentrations in the river. This result was limited by the uncertain hydro-climatic future of the contributing watershed. Climate change impacts in the downstream reservoir were far more apparent. Evaporative losses increased approximately 150% from the base model by the 2080–2100 period. Chlorophyll-a concentrations increased an average of 53% in this same period based on monthly mean percentage change. Reservoir water quality was improved after adding the interbasin water transfers. Results indicated that flow management would have a positive impact on water quality in the reservoir in the face of future climate change.

Assessing mercury pollution at a primary ore site with both ancient and industrial mining and smelting activities

The Minamata Convention on Mercury has mandated a renewed global effort to tackle Hg pollution. The present study evaluates Hg pollution at a primary Hg production site exploited since the Qin Dynasty (200s BC), with intensive industrial scale production over the past four decades. This single location accounts for over 95% total Hg production in China in recent years. To assess the environmental risk and effectiveness of recently implemented control measures, we collected 90 soil samples, 60 plant tissue samples, 47 sediment samples, and 47 river water samples from the site and its vicinity. A site-specific conceptual site model was established based on the sources, migration transformation pathways of Hg pollutant and its exposure scenarios. The maximum soil Hg concentration reached 10,451 mg kg−1, posing a high health and ecological risk. Vegetable and crop Hg concentrations outside the site reached 0.23 mg kg−1 in rice grains and 4.24 mg kg−1 in green onion. The highest health risk, with a hazard quotient of 130.66, was observed in the Ore Storage Site, which reduced to 17.14 when Hg bioavailability was considered. Risk control measures implemented in recent years included a stormwater collection system and capping of the tailing pond area with clean imported soil. These measures were generally successful; however, Hg in the tailings were found to be contaminating the imported surficial soil due to rainfall saturation and upward migration, suggesting a need for long-term post remedial site monitoring and maintenance. We also found that mining and smelting activities have contaminated a 6 km stretch of a nearby river, with sediment Hg concentrations reaching 2819 mg kg−1, and water column concentrations reaching 193.21 ng L−1. The sediment and water concentrations are highly correlated (R2 = 0.78), suggesting that, with risk control measures in place, a reservoir of Hg in polluted river sediment is now driving pollution in the water column. This work demonstrates that primary Hg mining has caused widespread and serious soil and water pollution. Risk control measures can reduce human health and ecological risks, but robust monitoring and maintenance are required for remediation to be effective in the long-term.

Relevance of photocatalytic redox transformations of selected pharmaceuticals in a copper- and iron-rich Mediterranean intermittent river

This work aimed at investigating specific attenuation pathways of pharmaceuticals in copper- and iron-rich Mediterranean intermittent and sunlit rivers by combining lab- and field-scale studies. Poorly photodegradable and biodegradable compounds such as fluconazole, oxazepam and venlafaxine attenuated in two river stretches with short hydraulic residence times (<3 h). This result was assumed to be related to their capacity to interact with photoreactive free Cu2+ and Fe3+ or their associated oxides. Lab-scale photodegradation experiments under simulated solar irradiation revealed the beneficial impact of a mixture Cu2+ and colloidal iron hydroxides at environmental concentrations and at neutral pH on the pharmaceuticals photodegradation kinetic rate constants. These latter were consistent with the in-stream attenuation rate constants of targeted contaminants which ranged from 0.104 to 0.154 h−1. Further identification of phototransformation products by LC-HRMS highlighted reductive transformation pathways including reductive dehalogenation and hydrogenation reactions. Several TPs were found to be stable under irradiation and were detected in field monitoring, accordingly. This was ascribed to the formation of a Cu/Fe composite material under solar irradiation with photocatalytic properties. The role of Cu was to trap the electron in the conduction band of the iron-based photocatalyst, which promoted separation efficiency of electron-hole pairs as well as enhanced photoreduction processes at the expense of oxidation ones. Even though, these mechanisms have been reported in water treatment field for organic micropollutants removal, their significance was demonstrated for the first time in natural settings.

Phytoplankton community as monitoring tool in the terminal stretch of a micro-tidal estuary facing the Tyrrhenian Sea

Mediterranean coastal systems, particularly those characterized by river mouths, have played an important role in the history of human civilization, thanks to unique species assemblages, a high biodiversity, and complex ecological interactions. The overlapping of multiple cross-scale effects, triggered by the ongoing climate change, makes these systems particularly important sites for ecological studies. Here, we have investigated the phytoplankton community structure in the terminal stretch of the Sele River (Tyrrhenian Sea) under two different hydrological regimes: i) with river mouth occluded by sediments preventing water exchange with the sea; ii) with river mouth completely opened, which allowed the maximum water mass exchanges between the river and the sea. The strong variations in physical-chemical properties of the water column, the point-distribution of total phytoplankton biomass, and the dominance of cryptophytes and cyanophytes under occluded and opened river mouth, respectively, indicate the presence of strong allogenic pressures acting on the system. Our data suggest that the monitoring of phytoplankton communities in the terminal stretch of micro-tidal estuaries, could be a useful tool for studying the extent of climate change underway in Mediterranean coastal marine areas.

Release of arsenic during riverbank filtration under anoxic conditions linked to grain size of riverbed sediments

Geogenic arsenic contamination of groundwater poses a health threat to millions of people worldwide, particularly in Asia. Riverbank filtration (RBF) is a pre-treatment technique that aims to improve surface water quality through natural processes during water infiltration before abstraction. A study in Hanoi, Vietnam is presented, where the water quality of 48 RBF wells from 5 large well fields located in the Pleistocene aquifer along the Red River was analyzed. >80 % of the wells had arsenic concentrations above the WHO limit of 10 μg/l. The riverbed sediment and riverbed pore-water from 23 sites along a stretch of 30 km of the Red River near the well fields was also analyzed. Muddy riverbeds were found to be a hotspot for arsenic release. Already at a 30 cm depth from the riverbed sediment surface, the pore-water at many sites had high concentrations of arsenic (>100 μg/l). Arsenic concentrations in the pore-water of sites where mud lenses were present in the riverbed were significantly higher compared to sites with sandy riverbeds. At well fields along stretches of the Red River where riverbed was mostly muddy, higher arsenic concentrations were found than at well fields where the riverbed was mostly sandy. This indicates that river muds deposition and river morphology can influence arsenic concentrations in the aquifer in Hanoi and potentially other RBF sites in regions with geogenic arsenic contamination. At the end, recommendations regarding site selection of new potential RBF wells in affected regions is given.

Use of water accounts based indicators for water management in India

AbstractIn India, water accounts on a river basin scale are not prepared regularly, mainly due to the unavailability of data on consumptive uses in various economic sectors at that scale. This research paper demonstrates an approach to prepare water accounts for the Mahanadi river basin in eastern India, which experiences climate‐induced hydrological extremes using the demographic, economic, hydrological, and geohydrological data available at different administrative and geographical scales. Further, selected water accounts derived indicators were computed to identify critical elements that need to be altered for improving water resources management at the river basin scale. The results show that the total inflow during the wet year exceeds 24%–26% in comparison to the normal and dry years. In turn, 23% and 24% of the inflow get drains to the sea in a dry and normal year, respectively, with agriculture accounting for the lion's share of the blue water consumed, about 57%–60% in all the years. The river has a huge dilution capacity, and, except for the biological oxygen demand in a dry year, the value of all other selected water quality parameters (nitrogen and electrical conductivity) is within the acceptable limits established by law. Reducing water consumption in irrigated crops during summer, controlling evaporation from the reservoirs, and considering nitrogen concentration and electrical conductivity in the existing approach to determine polluted river stretches in India are identified as crucial actions for improving water management in the basin. Further, assessment of water consumption and environmental flow requirement is identified as important decision factors to guide future water reallocation among riparian states.

Automated fluvial hydromorphology mapping from airborne remote sensing

AbstractMapping fluvial hydromorphology is an important part of defining river habitat. Mapping via field sampling or hydraulic modeling is however time consuming, and mapping hydromorphology directly from remote sensing data may offer an efficient solution. Here, we present a system for automated classification of fluvial hydromorphology based on a deep learning classification scheme applied to aerial orthophotos. Using selected rivers in Norway, we show how surface flow patterns (smooth or rippled surfaces vs. standing waves) can be classified in imagery using a trained convolutional neural network (achieving a training and validation accuracy of &gt;95%). We show how integration of these classified surface flow patterns with information on channel gradient, obtained from airborne topographic LiDAR data, can be used to compartmentalize the rivers into hydromorphological units (HMUs) that represent the dominant flow features. Automated classifications were broadly consistent with manual classifications that had been made in previous ground surveys, with equivalency in automated and manually derived HMU classes ranging from 61.5% to 87.7%, depending on the river stretch considered. They were found to be discharge‐dependent, showing the temporally dynamic aspect of hydromorphology. The proposed system is quick, flexible, generalizable, and provides consistent classifications free from interpretation bias. The deep learning approach used here can be customized to provide more detailed information on flow features, such as delineating between standing waves and advective diffusion of air bubbles/foam, to provide a more refined classification of surface flow patterns, and the classification approach can be further advanced by inclusion of additional remote sensing methods that provide further information on hydromorphological features.