scholarly journals Low Diffusive Methane Emissions From the Main Channel of a Large Amazonian Run-of-the-River Reservoir Attributed to High Methane Oxidation

2021 ◽  
Vol 9 ◽  
Author(s):  
Henrique O. Sawakuchi ◽  
David Bastviken ◽  
Alex Enrich-Prast ◽  
Nicholas D. Ward ◽  
Plínio B. Camargo ◽  
...  
Keyword(s):  
River Flow ◽  
Main Channel ◽  
Oxidation Rates ◽  
Initial Stage ◽  
River Reservoir ◽  
Stable Isotopic ◽  
Hydropower Dams ◽  
Littoral Sediment ◽  
Large Production ◽  
Flooded Areas

The global development of hydropower dams has rapidly expanded over the last several decades and has spread to historically non-impounded systems such as the Amazon River’s main low land tributaries in Brazil. Despite the recognized significance of reservoirs to the global methane (CH4) emission, the processes controlling this emission remain poorly understood, especially in Tropical reservoirs. Here we evaluate CH4 dynamics in the main channel and downstream of the Santo Antônio hydroelectric reservoir, a large tropical run-of-the-river (ROR) reservoir in Amazonia. This study is intended to give a snapshot of the CH4 dynamics during the falling water season at the initial stage after the start of operations. Our results show substantial and higher CH4 production in reservoirs’ littoral sediment than in the naturally flooded areas downstream of the dam. Despite the large production in the reservoir or naturally flooded areas, high CH4 oxidation in the main channel keep the concentration and fluxes of CH4 in the main channel low. Similar CH4 concentrations in the reservoir and downstream close to the dam suggest negligible degassing at the dam, but stable isotopic evidence indicates the presence of a less oxidized pool of CH4 after the dam. ROR reservoirs are designed to disturb the natural river flow dynamics less than traditional reservoirs. If enough mixing and oxygenation remain throughout the reservoir’s water column, naturally high CH4 oxidation rates can also remain and limit the diffusive CH4 emissions from the main channel. Nevertheless, it is important to highlight that our results focused on emissions in the deep and oxygenated main channel. High emissions, mainly through ebullition, may occur in the vast and shallow areas represented by bays and tributaries. However, detailed assessments are still required to understand the impacts of this reservoir on the annual emissions of CH4.

scholarly journals Hydraulic Evaluation of the Levee System Evolution on the Kurobe Alluvial Fan in the 18th and 19th Centuries

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4406
Author(s):  
Tadaharu Ishikawa ◽  
Hiroshi Senoo
Keyword(s):  
Channel Capacity ◽  
Flood Control ◽  
River Flow ◽  
Global Climate ◽  
Flow Simulation ◽  
Japan Sea ◽  
Main Channel ◽  
Alluvial Fan ◽  
Flood Peak ◽  
Levee System

The development process and flood control effects of the open-levee system, which was constructed from the mid-18th to the mid-19th centuries, on the Kurobe Alluvial Fan—a large alluvial fan located on the Japan Sea Coast of Japan’s main island—was evaluated using numerical flow simulation. The topography for the numerical simulation was determined from an old pictorial map in the 18th century and various maps after the 19th century, and the return period of the flood hydrograph was determined to be 10 years judging from the level of civil engineering of those days. The numerical results suggested the followings: The levees at the first stage were made to block the dominant divergent streams to gather the river flows together efficiently; by the completed open-levee system, excess river flow over the main channel capacity was discharged through upstream levee openings to old stream courses which were used as temporary floodways, and after the flood peak, a part of the flooded water returned to the main channel through the downstream levee openings. It is considered that the ideas of civil engineers of those days to control the floods exceeding river channel capacity, embodied in their levee arrangement, will give us hints on how to control the extraordinary floods that we should face in the near future when the scale of storms will increase due to the global climate change.

scholarly journals Experimental Study of Submerged Vanes in Intakes under Sediment Feeding Conditions

2018 ◽  
Vol 40 ◽  
pp. 03016
Author(s):  
Aslı Bor Türkben
Keyword(s):  
Water Intake ◽  
River Flow ◽  
Flow Direction ◽  
Main Channel ◽  
Bed Topography ◽  
Before And After ◽  
Submerged Vane ◽  
Solid Discharge ◽  
Submerged Vanes ◽  
Intake Structure

Sediment is transported along the river flow and deposited in the mouth of the intake structure over time and reducing the water intake capacity. Nowadays, many water intake structures lose their function and are closed to operation. To deal with this problem, recently, submerged vane application has offered a practical and economical solution. The aim of this study was to evaluate the efficiency of three vane installations under sediment feeding conditions by comparing the bed topography before and after vanes were installed. For that purpose, experiments were carried out in a laboratory channel running for 90-degree intake angle. Three vanes were installed in one column at near the intake entrance. The vanes dimensions were equal to; 3cm height, 12cm long, 10 mm thick, and aligned with α = 20° angle to flow direction. The tests were run until equilibrium was reached, i.e. when the outgoing solid discharge was equal or larger than 90% of the incoming. Once the bed topography remained stable, bed and water level surfaces were measured. tests were carried out by feeding sediment from upstream of the main channel.

scholarly journals Abundance and Activity of Methanotrophic Bacteria in Littoral and Profundal Sediments of Lake Constance (Germany)

2008 ◽  
Vol 75 (1) ◽  
pp. 119-126 ◽  
Author(s):  
M. Rahalkar ◽  
J. Deutzmann ◽  
B. Schink ◽  
I. Bussmann
Keyword(s):  
Methane Oxidation ◽  
Lake Constance ◽  
Type I ◽  
Sediment Depth ◽  
Oxidation Activity ◽  
Oxidation Rates ◽  
Methane Oxidizing Bacteria ◽  
Littoral Sediment ◽  
Sediment Layers

ABSTRACT The abundances and activities of aerobic methane-oxidizing bacteria (MOB) were compared in depth profiles of littoral and profundal sediments of Lake Constance, Germany. Abundances were determined by quantitative PCR (qPCR) targeting the pmoA gene and by fluorescence in situ hybridization (FISH), and data were compared to methane oxidation rates calculated from high-resolution concentration profiles. qPCR using type I MOB-specific pmoA primers indicated that type I MOB represented a major proportion in both sediments at all depths. FISH indicated that in both sediments, type I MOB outnumbered type II MOB at least fourfold. Results obtained with both techniques indicated that in the littoral sediment, the highest numbers of methanotrophs were found at a depth of 2 to 3 cm, corresponding to the zone of highest methane oxidation activity, although no oxygen could be detected in this zone. In the profundal sediment, highest methane oxidation activities were found at a depth of 1 to 2 cm, while MOB abundance decreased gradually with sediment depth. In both sediments, MOB were also present at high numbers in deeper sediment layers where no methane oxidation activity could be observed.

Effect of Ti Addition on Oxidation Behavior and Area Specific Resistance of Fe-20Cr Alloys for SOFC Interconnects

2014 ◽  
Vol 660 ◽  
pp. 249-253 ◽  
Author(s):  
Zaka Ruhma ◽  
Asep Ridwan Setiawan ◽  
Aditianto Ramelan ◽  
Rochim Suratman
Keyword(s):  
Oxidation Behavior ◽  
Specific Resistance ◽  
Parabolic Rate Constant ◽  
Xrd Analysis ◽  
Oxidation Rates ◽  
Air Atmosphere ◽  
Ti Alloys ◽  
Initial Stage ◽  
Area Specific Resistance ◽  
Ti Addition

In this work, the oxidation behavior of Fe-20wt.%Cr alloys with different titanium contents: 0, 0.5, and 1 wt.% are studied as a function of time in air atmosphere. The samples were isothermally oxidized at 700°C for 24, 48, and 96 h in a box furnace. The area specific resistance of oxides formed at the alloys surface during oxidation is measured by four-point probe methods at 700°C for 24 h. For Ti containing alloys, surface morphology observation by SEM shows that a few of TiO2 particles formed on the top of Cr2O3 scales. Continous TiO2 layer was not formed at the alloys surface after oxidation. XRD analysis on the oxide scales of Fe-20Cr-Ti alloys confirms that Cr2O3 and TiO2 oxide formed on the alloys. Ti addition into the alloys increases the oxidation rates of alloys at the initial stages. Oxidation behavior of Fe-20Cr-0.5Ti and Fe-20Cr-1Ti alloys showed two regimes. The parabolic rate constant, kp (in gr2/cm4s) were 1.57 x 10-13 and 3.08 x 10-13 respectively for initial stage of oxidation then changed to-9 x 10-15 and-3 x 10-14 respectively for the remainder of the test. ASR measurement shows that the presence of Ti in the alloys decreases the electrical resistance up to 60%. Ti addition into Fe-Cr alloys affect the oxide growth rate and increase the conductivity of Cr2O3 scales.

scholarly journals Bathymetric components towards ensuring navigable channel along a section of lower river Niger, lokoja, kogi state, Nigeria

2021 ◽  
Vol 5 (5) ◽  
pp. 231-238
Author(s):  
Olanrewaju M Oye ◽  
Lawrence Hart ◽  
Sika Orupabo
Keyword(s):  
Flow Velocity ◽  
River Flow ◽  
Classical Method ◽  
Research Work ◽  
Economic Benefits ◽  
Main Channel ◽  
Secondary Channel ◽  
Cross Sectional ◽  
Single Beam ◽  
River Niger

Navigation in Lower River Niger is seasonal because of insufficient water depth during the dry season. This is a limitation to economic benefits derivable compared to when the river is navigable throughout the year. Government and stakeholders alike have exerted efforts in the past years to create an unimpeded navigable channel without much success. The need to ensure all-year-round navigation in the Lower River Niger for industrial and commercial purposes necessitated this research work. The main thrust of this work is to determine bathymetric components parameters of the river necessary for the design of an appropriate river training structure to divert river flow from the secondary channel to the main channel. The specific objective hereto is to assess the extent and geometry of the river banks, the configuration of the river bed, the river flow velocity and discharge. The approach deployed in this work is the classical method of acoustic principle premised on Remote Sensing techniques. The shape of the river was obtained through waypoint survey using Garmin eTrex 10 handheld GPS, while the riverbed configuration was determined through bathymetric survey using Odom Echotrack MK III single beam Echo Sounder and the flow velocity data was acquired using Valeport 106 Current Meter. Data processing and analysis were achieved using Garmin Basecamp 4.7.3, Wintopo V7.03, Valeport Datalog X2 and Surfer 13 software. The length of the study area measured along the main channel was obtained as 5.94km while that of secondary channel gave 4.30km. Area occupied by the main channel was found to be 2,636,331.3m2 and 1,759,045.4m2 for the secondary channel. Average depth on the main channel was 0.21m while on the secondary channel was -0.89m, depth figures referred to Lokoja local datum. The average flow velocity was obtained to be 0.449m/s and the cross-sectional area of the river as 1568.75m2, which gave a value of 704.2m3/s for the river discharge. The research produced the digital terrain model (DTM) and bathymetric charts of the study area. The parameters obtained in this study is a useful tool in defining an appropriate embankment dam suitable to divert the flow from the secondary channel to the main channel to enhance depth towards all-season navigation in Lower River Niger.

scholarly journals High water level observations along the upper course of the Olt River (Romania) from a hydrological modelling aspect

2017 ◽  
Vol 11 (2) ◽  
pp. 10-19
Author(s):  
Noémi Mária Szopos ◽  
Boglárka Czellecz
Keyword(s):  
Hydrological Modeling ◽  
River Flow ◽  
High Water ◽  
Main Channel ◽  
Flood Events ◽  
River Section ◽  
Modeling Software ◽  
Section Model ◽  
Hydrometric Station ◽  
River Cross Section

Along its upper course, the Olt River (Romania) flows through several settlements, which are endangered by flooding. The multiannual water flow at Tomești station, the first hydrometric station along the Olt River, is 1.51 m3 /s, but in case of extreme events the river flow reached even 41.8 m3 /s. The aim of this study is to analyze the flood events along the upper course of the Olt River (section between Tomești and Cârța settlements) by using the HEC-RAS and the HEC-GeoRAS hydrological modeling software programs. The river cross section model showed how the main channel narrowed (characteristic to some locations) which can be considered as one of the causes of a possible overflow.

scholarly journals Hydrodynamic Condition Modeling along the North-Central Coast of Vietnam

2020 ◽  
Vol 10 (3) ◽  
pp. 5648-5654
Author(s):  
D. D. Cham ◽  
N. T. Son ◽  
N. Q. Minh ◽  
N. T. Hung ◽  
N. Tien Thanh
Keyword(s):  
Sediment Transport ◽  
River Flow ◽  
Morphological Changes ◽  
Main Channel ◽  
Low Flow ◽  
Hydrodynamic Condition ◽  
Central Coast ◽  
North Central ◽  
The North ◽  
Coast Of Vietnam

An extremely dynamic morphology of the estuary is observed in the coastal regions of Vietnam under the governing processes of tides, waves, and river system flows. The primary target of this paper is to provide insight into the governing processes and morphological behavior of the NhatLe estuary, located in the north-central coast of Vietnam. Based on measured data from field surveys and satellite images combined with numerical model simulations of MIKE and Delft3D, the influences of seasonal river flow, tides, and wave dynamics on the sediment transport and morphological changes are fully examined. The study showed that freshwater flow in the flood season plays a central role in cutting off the southern sandspit, maintain and shaping the main channel. The prevailing waves in winter and summer induce longshore drift and sediment transport in the southeast to northwest direction. In the low flow season, this longshore sediment transport is dominant, causing sediment to deposit on the southern side of the ebb tidal delta and elongating the southern sandspit which narrows the estuary entrance and reorients the main channel.

scholarly journals Widespread dieback of riparian trees on a dammed ephemeral river and evidence of local mitigation by tributary flows

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2622 ◽  
Author(s):  
Caitlin M. S. Douglas ◽  
Mark Mulligan ◽  
Xavier A. Harrison ◽  
Joh R. Henschel ◽  
Nathalie Pettorelli ◽  
...  
Keyword(s):  
Channel Flow ◽  
River Flow ◽  
Main Channel ◽  
Riparian Trees ◽  
Ephemeral Rivers ◽  
Riparian Tree ◽  
Tree Dieback ◽  
Anthropogenic Threats ◽  
Individual Trees ◽  
Key Resources

Ephemeral rivers act as linear oases in drylands providing key resources to people and wildlife. However, not much is known about these rivers’ sensitivities to human activities. We investigated the landscape-level determinants of riparian tree dieback along the Swakop River, a dammed ephemeral river in Namibia, focusing on the native ana tree (Faidherbia albida) and the invasive mesquite (Prosopisspp.). We surveyed over 1,900 individual trees distributed across 24 sites along a 250 km stretch of the river. General linear mixed models were used to test five hypotheses relating to three anthropogenic threats: river flow disruption from damming, human settlement and invasive species. We found widespread dieback in both tree populations: 51% mortality in ana tree, with surviving trees exhibiting 18% canopy death (median); and 26% mortality in mesquite, with surviving trees exhibiting 10% canopy death. Dieback in the ana tree was most severe where trees grew on drier stretches of the river, where tributary flow was absent and where mesquite grew more abundantly. Dieback in the mesquite, a more drought-tolerant taxon, did not show any such patterns. Our findings suggest that dieback in the ana tree is primarily driven by changes in river flow resulting from upstream dam creation and that tributary flows provide a local buffer against this loss of main channel flow. The hypothesis that the invasive mesquite may contribute to ana tree dieback was also supported. Our findings suggest that large dams along the main channels of ephemeral rivers have the ability to cause widespread mortality in downstream riparian trees. To mitigate such impacts, management might focus on the maintenance of natural tributary flows to buffer local tree populations from the disruption to main channel flow.

scholarly journals Distribution of stable isotopes in water from an alpine river in China

2018 ◽  
Vol 13 (2) ◽  
pp. 371-381 ◽  
Author(s):  
Yuchuan Meng ◽  
Guodong Liu
Keyword(s):  
Isotopic Composition ◽  
Water Temperature ◽  
River Water ◽  
River Flow ◽  
Main Stream ◽  
The Tibetan Plateau ◽  
Stable Isotopic ◽  
Alpine River ◽  
Eastern Edge

Abstract The Hailuogou River, on the south-eastern edge of the Tibetan Plateau, receives a substantial portion of its flow from meltwater. The stable isotopic composition and water temperature were observed for waters collected from the main stream and selected tributaries. The results indicate that the river water is generally more depleted in 18O and 2H than groundwater, but more enriched than meltwater. The river water in the upper reaches is characterised by more negative isotopic values, the isotopic fingerprint of meltwaters, and lower temperatures. Both δ18O and δ2H increase significantly during passage from the upper basin downward, at least partly due to enrichment from tributary-inputs. There are also an altitude δ18O-effect of −0.1‰ per 100-m rise, and an altitude δ2H-effect of −0.8‰ per 100-m rise, along the main stream. The positive correlation between isotopic composition and water temperature further highlights the role of meltwater in regulating the river's isotope hydrology. The fraction of meltwater inputs over the total river flow ranges from 67% at Section 11 to 89% at Section 7, in the proglacial headwater region. The tributary-input enrichments and ice-snow melting are the main mechanisms controlling the isotopic composition of river runoff, but depending strongly on altitude.

scholarly journals Geo-disaster Laharic Flow along Putih River, Central Jawa, Indonesia

2015 ◽  
Vol 3 (2) ◽  
Author(s):  
Sugeng Sapto Surjono ◽  
Ahmad Yufianto
Keyword(s):  
Surface Water ◽  
Debris Flow ◽  
River Flow ◽  
Early Period ◽  
Main Channel ◽  
Point Of View ◽  
Volcanic Material ◽  
Central Java ◽  
Hyperconcentrated Flow ◽  
Downstream Area

In 2011, laharic flow transporting volcanic materials had significantly occurred along Putih River, causing severe damage in Jumoyo area, Magelang, Central Java, Indonesia. The disaster happened frequently until April 2011. The approximately 150 million cubic meter of volcanic materials expelled from 2010 Merapi eruption has been assumed as main cause of recent laharic flow. Although pyroclastic deposit mostly flew to south and southeastern direction through Woro, Gendol, and Opak Rivers, laharic flow apparently flew to the west – westward directions through Putih and Pabelan Rivers. This study will explain the mechanism of such disaster along Putih River from sedimentological point of view. Transport mechanism of laharic flow along river is strongly controlled by the slope and type of fluids. In the upper stream area, debris flow commonly occurs as gravity flow in the steep slope. To the downstream area, where more river and surface water infiltrates the volcanic material transportation, laharic flow mechanism transforms to hyperconcentrated flow. In the gently slope area, laharic flow decreases in concentration but increase in amount because of the accumulation influx from several river flows. Hyperconcentrated flow in Putih River is mostly generated by accumulation of river flow in the tributary area. In such area, loose volcanic materials are eroded easily by surface water. Rill and gully erosion bring volcanic material into main channel of Putih River, followed by intensive vertical erosion along upper stream that will produce bigger accumulation of volcanic material within laharic flow in the downstream area. Several sabo dams along the Putih River were damaged during early period of laharic flow due to this transportation mechanism. At the downstream of in Gempol Village, Jumoyo Area, the main channel of Putih River is shifting northwestward significantly due to Gendol Hill. On the other hand, river body in this settlement area is narrower compared to the upper stream area just before turning point. Both condition cause laharic flow to spill out from the channel and form an unconfined sheet debris flow with a 500 m width and around 2-4 m thick sediments. Although energy of transport is reduced significantly, but this flow is still able to transport abundant volcanic material ranging from silt to boulder. Traditional market and hundreds of houses were buried and the main road from Yogyakarta to Magelang city has been disconnected for several times due to this disaster. Keywords: Putih River, Laharic flow, Jumoyo

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