scholarly journals Quantifying Suspended Sediment using Acoustic Doppler Current Profiler in Tidung Island Seawaters

2021 ◽  
Vol 29 (1) ◽  
Author(s):  
Henry Munandar Manik ◽  
Randi Firdaus
Keyword(s):  
Water Column ◽  
Suspended Sediment ◽  
Suspended Solids ◽  
Acoustic Doppler Current Profiler ◽  
Sediment Concentration ◽  
In Situ Measurement ◽  
Ocean Current ◽  
Echo Intensity ◽  
Current Profiler

Tidung Island, located near Jakarta Bay, is a tourism and conservation area. It is necessary to keep these seawaters unpolluted. To calculate the level of pollution, it is necessary to know the sediment concentration. Quantifying concentration suspended sediment is important for knowledge of sediment transport. Researchers usually use water sample analysis and optical method for quantifying suspended sediment in seawater. Less accuracies of these methods are due to under sample of seawater and the existence of biological fouling. One promising method to measure concentration of suspended sediment is using Acoustic Doppler Current Profiler (ADCP). ADCP is usually used by oceanographer and hydrographer to measure ocean current. In this research, ADCP with 300 kHz operating frequency was used effectively to measure suspended sediment concentration (SSC) and ocean current simultaneously. The echo intensity received from suspended sediment was computed using sonar equations to quantify SSC. The empirical equation between echo intensity and SSC was found. The SSC value obtained by ADCP was also compared with in situ measurement. The result showed that quantified SSC value obtained by ADCP was nearly equal with SSC obtained from in situ measurement with coefficient correlation of 0.98. The high concentration ranged from 55 mg/L to 80 mg/L at the surface layer to a depth 12 m, moderate concentration ranged from 45 mg/L to 55 mg/L at a depth 12 m to 40 m, and low concentration less than 45 mg/L at a depth greater than 40 m. The distribution of SSC was correlated with ocean current condition. In small currents, suspended solids will settle faster so that the concentration in the water column will decrease. Conversely, if the velocity is high, suspended solids will continue to float carried by the current in the water column so that the concentration is high.

An Instrument With Constant Volume Approach for In Situ Measurement of Surface Runoff and Suspended Sediment Concentration

2021 ◽  
Vol 57 (2) ◽  
Author(s):  
Xiaoyun Zhan ◽  
Jun Zhao ◽  
Xia Zhu‐Barker ◽  
Junfeng Shui ◽  
Baoyuan Liu ◽  
...  
Keyword(s):  
Suspended Sediment ◽  
Surface Runoff ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration ◽  
Constant Volume ◽  
In Situ Measurement

Extracting Meaningful Information from Uncalibrated Backscattered Echo Intensity Data

2010 ◽  
Vol 27 (5) ◽  
pp. 943-949 ◽  
Author(s):  
Louis Gostiaux ◽  
Hans van Haren
Keyword(s):  
Transmission Loss ◽  
Signal To Noise Ratio ◽  
Acoustic Doppler Current Profiler ◽  
Sediment Concentration ◽  
Original Method ◽  
Air Bubbles ◽  
Echo Intensity ◽  
The North ◽  
Current Profiler ◽  
The North Sea

Abstract The authors present an original method for the analysis of acoustic Doppler current profiler (ADCP) echo intensity profiles measured in the ocean, especially when no calibration has been performed. This study is based on data from Teledyne RD Instrument acoustic profilers but provides a methodology that can be extended to other kinds of hardware. To correctly interpret data for which the signal-to-noise ratio is below a factor of 10, the authors propose isolating the backscattered signal from noise in arithmetic space before resolving the sonar equation and compensating for transmission loss in logarithmic space. The robustness of the method is shown for several independent datasets from the Atlantic Ocean, the North Sea, and the Mediterranean Sea. Estimation of sediment concentration, planktonic migrations, or air bubbles is now possible at less than 10 dB above noise level, which can concern half of the ADCP’s range under common circumstances.

scholarly journals Volumetric Mapping of Methane Concentrations at the Bush Hill Hydrocarbon Seep, Gulf of Mexico

2021 ◽  
Vol 9 ◽  
Author(s):  
William P. Meurer ◽  
John Blum ◽  
Greg Shipman
Keyword(s):  
Gulf Of Mexico ◽  
Water Column ◽  
Acoustic Doppler Current Profiler ◽  
Field Studies ◽  
Methane Seepage ◽  
Current Profiler ◽  
Methane Fluxes ◽  
Methane Concentrations

The role of methane as a green-house gas is widely recognized and has sparked considerable efforts to quantify the contribution from natural methane sources including submarine seeps. A variety of techniques and approaches have been directed at quantifying methane fluxes from seeps from just below the sediment water interface all the way to the ocean atmosphere interface. However, there have been no systematic efforts to characterize the amount and distribution of dissolved methane around seeps. This is critical to understanding the fate of methane released from seeps and its role in the submarine environment. Here we summarize the findings of two field studies of the Bush Hill mud volcano (540 m water depth) located in the Gulf of Mexico. The studies were carried out using buoyancy driven gliders equipped with methane sensors for near real time in situ detection. One glider was equipped with an Acoustic Doppler Current Profiler (ADCP) for simultaneous measurement of currents and methane concentrations. Elevated methane concentrations in the water column were measured as far away as 2 km from the seep source and to a height of about 100 m above the seep. Maximum observed concentrations were ∼400 nM near the seep source and decreased away steadily in all directions from the source. Weak and variable currents result in nearly radially symmetric dispersal of methane from the source. The persistent presence of significant methane concentrations in the water column points to a persistent methane seepage at the seafloor, that has implications for helping stabilize exposed methane hydrates. Elevated methane concentrations in the water column, at considerable distances away from seeps potentially support a much larger methane-promoted biological system than is widely appreciated.

scholarly journals Prediction and classification of suspended sediment and zooplankton signals from acoustic Doppler current profiler backscatter data using artificial neural networks

2021 ◽  
Vol 944 (1) ◽  
pp. 012014
Author(s):  
A Dwinovantyo ◽  
S Solikin ◽  
H M Manik ◽  
T Prartono ◽  
Susilohadi
Keyword(s):  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Acoustic Doppler Current Profiler ◽  
Suspended Sediments ◽  
Sediment Concentration ◽  
Optimal Number ◽  
Environmental Data ◽  
Zooplankton Abundance ◽  
Current Profiler ◽  
Artificial Neural

Abstract Characterization of each underwater object has its challenges, especially for small objects. The process of quantifying acoustic signals for these small objects can be done using high-frequency hydroacoustic instruments such as an acoustic Doppler current profiler (ADCP) combined with the artificial intelligence (AI) technique. This paper presents an artificial neural network (ANN) methodology for classifying an object from acoustic and environmental data in the water column. In particular, the methodology was tuned for the recognition of suspended sediments and zooplankton. Suspended sediment concentration and zooplankton abundance, which extracted from ADCP acoustic data, were used as input in the backpropagation method along with other environmental data such as effects of tides, currents, and vertical velocity. The classifier used an optimal number of neurons in the hidden layer and a feature selection based on a genetic algorithm. The ANN method was also used to estimate the suspended sediment concentration in the future. This study provided new implications for predicting and classifying suspended sediment and zooplankton using the ADCP instrument. The proposed methodology allowed us to identify the objects with an accuracy of more than 95%.

scholarly journals Estimation of Suspended Sediment Concentration from Remote Sensing and In Situ Measurement over Lake Tana, Ethiopia

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Zelalem R. Womber ◽  
Fasikaw A. Zimale ◽  
Mebrahtom G. Kebedew ◽  
Bekalu W. Asers ◽  
Nikole M. DeLuca ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Water Quality ◽  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Temporal Distribution ◽  
Sediment Concentration ◽  
In Situ Measurement ◽  
Spatial And Temporal Distribution ◽  
Lake Tana

Discharge from basins joining a lake is the main factor determining the lake volume and sediment inflow to the lake. Suspended sediment is an important parameter for describing the water quality of aquatic ecosystems. Lake Tana is an important and the largest lake in Ethiopia for the local ecological system. However, environmental change and anthropogenic activities in the area threaten its water quality. The conventional methods of suspended sediment concentration (SSC) observation are unable to determine and compare spatial and temporal SSC patterns for the lake over a period of years. Remote sensing methods have made it possible to map SSC. The objective of this study is to characterize the spatial and temporal distribution of suspended sediment of Lake Tana using in situ measurement and remote sensing applications and specifically to develop a relationship between in situ and remote sensing observation to retrieve suspended sediment concentration and map the spatal distribution of SSC. This study used MODIS-Terra and in situ data to characterize the spatial and temporal distribution of SSC in the rainy season. Four sampling campaigns (20 samples per campaign) were carried out on Lake Tana, and the first three sampled campaigns on May 11–13, 2018, June 08–10, 2018, and July 15–17, 2018, were used for calibration of regression models. MODIS-Terra reflectance in NIR was found best related to in situ water quality data and varies linearly with SSC (r2 = 0.81) and turbidity (r2 = 0.85). Secchi disc depth (SDD) found the best fit for a power relation with NIR band reflectance (r2 = 0.74). The MODIS-Terra reflectance in red was found to be poorly related to in situ measurements. The relation in NIR reflectance was validated using the LOOCV (leave-one-out-cross-validation) technique and the fourth sampled data set collected on August 12–14, 2018. Developed models are validated with RMSE of 42.96 mg/l, 14.6 NTU, and 0.17 m, ARE of 23.3%, 27.6%, and 12.4%, and RRMSE of 25.1%, 44.5%, and 29.6% for SSC, turbidity, and SDD, respectively, using LOOCV. The equation was also validated using August 2018 collected data sets with RMSE of 87.6 mg/l, 11.7 NTU, 0.08 m, ARE of 20.8%, 25.9%, and 28.8%, and RRMSE of 17.8%, 20.5%, and 27.9% for SSC, turbidity, and SDD, respectively. Applying the developed regression model, a 10-year time series of SSC from 2008–2017 for May-August was estimated and the trend was tested using the Mann–Kendall trend test. It was found that an increasing trend was observed from the period 2008 to 2017. The result shows that satellite data like the MODIS-Terra imagery could be used to monitor and obtain past records of SSC with the developed equation. The increasing SSC can be reduced by implementing selected management practices in the surrounding watersheds of the lake to reduce nutrient and sediment inflow.

Variability of the Horizontal Velocity Structure in the Upper 1600 m of the Water Column on the Equator at 10°W

2006 ◽  
Vol 36 (7) ◽  
pp. 1287-1304 ◽  
Author(s):  
Lucia Bunge ◽  
Christine Provost ◽  
Jonathan M. Lilly ◽  
Marc D’Orgeville ◽  
Annie Kartavtseff ◽  
...  
Keyword(s):  
Water Column ◽  
Velocity Component ◽  
Velocity Structure ◽  
Strong Dependence ◽  
Acoustic Doppler Current Profiler ◽  
Horizontal Velocity ◽  
Vertical Shear ◽  
Equatorial Atlantic ◽  
Entire Water Column ◽  
Current Profiler

Abstract This paper presents initial results from new velocity observations in the eastern part of the equatorial Atlantic Ocean from a moored current-meter array. During the “EQUALANT” program (1999–2000), a mooring array was deployed around the equator near 10°W that recorded one year of measurements at various depths. Horizontal velocities were obtained in the upper 60 m from an upward-looking acoustic Doppler current profiler (ADCP) and at 13 deeper levels from current meters between 745 and 1525 m. To analyze the quasiperiodic variability observed in these records, a wavelet-based technique was used. Quasiperiodic oscillations having periods between 5 and 100 days were separated into four bands: 5–10, 10–20, 20–40, and 40–100 days. The variability shows (i) a strong seasonality (the first half of the series is dominated by larger periods than the second one) and (ii) a strong dependence with depth (some oscillations are present in the entire water column while others are only present at certain depths). For the oscillations that are present in the entire water column the origin of the forcing can be traced to the surface, while for the others the question of their origin remains open. Phase shifts at different depths generate vertical shears in the horizontal velocity component with relatively short vertical scales. This is especially visible in long-duration events (>100 days) of the zonal velocity component. Comparison with a simultaneous lowered acoustic Doppler current profiler (LADCP) section suggests that some of these flows may be identified with equatorial deep jets. A striking feature is a strong vertical shear lasting about 7 months between 745 and 1000 m. These deep current-meter observations would then imply a few months of duration for the jets in this region.

scholarly journals Turbulence and hypoxia contribute to dense biological scattering layers in a Patagonian fjord system

Ocean Science ◽  
2018 ◽  
Vol 14 (5) ◽  
pp. 1185-1206 ◽  
Author(s):  
Iván Pérez-Santos ◽  
Leonardo Castro ◽  
Lauren Ross ◽  
Edwin Niklitschek ◽  
Nicolás Mayorga ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Water Column ◽  
Turbulent Kinetic Energy ◽  
Tidal Flow ◽  
Vertical Mixing ◽  
Acoustic Doppler Current Profiler ◽  
Marine Species ◽  
Eddy Diffusivity ◽  
Diel Vertical Migrations

Abstract. The aggregation of plankton species along fjords can be linked to physical properties and processes such as stratification, turbulence and oxygen concentration. The goal of this study is to determine how water column properties and turbulent mixing affect the horizontal and vertical distributions of macrozooplankton along the only northern Patagonian fjord known to date, where hypoxic conditions occur in the water column. Acoustic Doppler current profiler moorings, scientific echo-sounder transects and in situ plankton abundance measurements were used to study macrozooplankton assemblages and migration patterns along Puyuhuapi Fjord and Jacaf Channel in Chilean Patagonia. The dissipation of turbulent kinetic energy was quantified through vertical microstructure profiles collected throughout time in areas with high macrozooplankton concentrations. The acoustic records and in situ macrozooplankton data revealed diel vertical migrations (DVM) of siphonophores, chaetognaths and euphausiids. In particular, a dense biological backscattering layer was observed along Puyuhuapi Fjord between the surface and the top of the hypoxic boundary layer (∼100 m), which limited the vertical distribution of most macrozooplankton and their DVM, generating a significant reduction of habitat. Aggregations of macrozooplankton and fishes were most abundant around a submarine sill in Jacaf Channel. In this location macrozooplankton were distributed throughout the water column (0 to ∼200 m), with no evidence of a hypoxic boundary due to the intense mixing near the sill. In particular, turbulence measurements taken near the sill indicated high dissipation rates of turbulent kinetic energy (ε∼10-5 W kg−1) and vertical diapycnal eddy diffusivity (Kρ∼10-3 m2 s−1). The elevated vertical mixing ensures that the water column is well oxygenated (3–6 mL L−1, 60 %–80 % saturation), creating a suitable environment for macrozooplankton and fish aggregations. Turbulence induced by tidal flow over the sill apparently enhances the interchange of nutrients and oxygen concentrations with the surface layer, creating a productive environment for many marine species, where the prey–predator relationship might be favored.

scholarly journals Developing of Total Suspended Sediment Model Using Landsat-8 Satellite Image and In-Situ Data at The Surabaya Coast, East Java, Indonesia

2017 ◽  
Vol 49 (1) ◽  
pp. 73 ◽  
Author(s):  
Teguh Hariyanto ◽  
Trismono C. Krisna ◽  
Khomsin Khomsin ◽  
Cherie Bhekti Pribadi ◽  
Nadjadji Anwar
Keyword(s):  
Water Quality ◽  
Suspended Sediment ◽  
Coastal Water ◽  
Satellite Image ◽  
Coastal Region ◽  
Sediment Concentration ◽  
Landsat 8 ◽  
Total Suspended Sediment ◽  
Coastal Water Quality

The decrease of coastal-water quality in the Surabaya coastal region can be recognized from the conceentration of Total Suspended Sediment(TSS ) . As a result we need a system for monitoring sediment concentration in the coastal region of Surabaya which regularly measures TSS. The principle to model and monitor TSSconcentration using remote sensing methods is by the integration of Landsat-8OLI satellites image processing using some ofTSS-models then those are analyzed for looking its suitability with TSS value direcly measured in the field ( in-situ measurement). The TSS value modeled from all algorithms validated usingcorrelation analysis and linear regression . The result shows that TSS model with the highest correlation value is TSS algorithm by Budiman (2004)with r value 0.991. Hence this algorithm can be used to investigate TSS-distribution which represent the coastal water quality of Surabaya with TSS value between 75 mg/L to 125 mg/L.

scholarly journals A Method for Processing Acoustic Doppler Current Profiler Velocity Data from Towed, Undulating Vehicles

2008 ◽  
Vol 25 (9) ◽  
pp. 1710-1716 ◽  
Author(s):  
Jiayi Pan ◽  
David A. Jay
Keyword(s):  
Surface Waters ◽  
High Frequency ◽  
Acoustic Doppler Current Profiler ◽  
Small Time ◽  
Ocean Current ◽  
Near Surface ◽  
Vertical Range ◽  
External Reference ◽  
Current Profiler ◽  
Adcp Measurements

Abstract The utility of the acoustic Doppler current profiler (ADCP) for sampling small time and space scales of coastal environments can be enhanced by mounting a high-frequency (1200 kHz) ADCP on an oscillating towed body. This approach requires both an external reference to convert the measured shears to velocities in the earth coordinates and a method to determine the towed body velocities. During the River Influence on the Shelf Ecosystems (RISE) project cruise, a high-frequency (1200 kHz) and narrowbeam ADCP with mode 12 sampling was mounted on a TRIAXUS oscillating towfish, which steers a 3D path behind the ship. This deployment approach extended the vertical range of the ADCP and allowed it to sample near-surface waters outside the ship’s wake. The measurements from a ship-mounted 1200-kHz narrowbeam ADCP are used as references for TRIAXUS ADCP data, and a method of overlapping bins is employed to recover the entire vertical range of the TRIAXUS ADCP. The TRIAXUS vehicle horizontal velocities are obtained by removing the derived ocean current velocity from the TRIAXUS ADCP measurements. The results show that the method is practical.

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