Difference between revisions of "Dilution gauging"

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(Created page with "=Quick summary= file:bms_sensor.png|thumb|500px|Figure 1: (a) Geophone and accelerometer installed in a watertight housing mounted on an impact plate and exemplary (b) geoph...")
 
 
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=Quick summary=
 
=Quick summary=
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[[file:bms_sensor.png|thumb|500px|Figure 1: (a) Geophone and accelerometer installed in a watertight housing mounted on an impact plate and exemplary (b) geophone and (c) accelerometer signal of the identical single grain impact. SumIMP denotes the total number of peaks above the threshold amplitude Amin for the event shown. Amaxmax is the maximum amplitude registered during this event. Only positive amplitude values are considered.]]
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[[file:dilution_gauging2.png|thumb|250px|Figure 1: Dilution gauging in a fishway: making the dilution of the tracer (Rhodamine Wt) (source: Itagra.ct).]]
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[[file:bms_vortex_tube.png|thumb|500px|Figure 2: (a) Conceptual sketch of the vortex tube functionality and (b) vortex tube outlet at HPP Schiffmühle (source: VAW).]]
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[[file:dilution_gauging3.png|thumb|250px|Figure 2: Dilution gauging in a fishway: Mariotte device for continuous injection into the fishway (source: Itagra.ct).]]
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[[file:bms_vortex_tube2.png|thumb|500px|Figure 3: (a) Vortex tube outlet with mounted sensors and (b) vortex tube running during the field calibration (source: VAW).]]
 
  
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Developed by: VAW, ETH Zurich, Switzerland; Test Case partner: Limmatkraftwerke AG, Baden, Switzerland
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Developed by:Francisco Javier Bravo, Itagra.ct
  
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Date: February 2019
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Date:
  
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Type: [[:Category:Devices|Device]]
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Type: [[:Category:Methods|Method]]
  
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Suitable for the following [[::Category:Measures|measures]]:
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=Introduction=
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This method requires the release of a known tracer concentration in a section of the river or fishway and the subsequent determination of the tracer concentration in a downstream section. It is based on the dilution relationships between the injection of the tracer and the discharge we want to know. There are two main different methods for the injection of the tracers into the flow: (a) instantaneous or integration method and (b) continuous method.
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The discharge for (a) is calculated as:
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<math>Q=\frac{c_0}{c}*\frac{V}{T}</math>
  
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=Introduction=
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being <math>Q={c_0}</math> the tracer concentration which is introduced in the watercourse with discharge ''Q''. ''c'' is the concentration of the sample in volume ''V'' and ''T'' is equal to the time needed for the tracer to be transported downstream.
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An indirect Bedload Monitoring System (BMS) is developed for bedload transport monitoring in the vortex tube system installed in the headwater channel of the FIThydro case study hydropower plant (HPP) Schiffmühle. The BMS allows the quantitative assessment of bedload transport in rivers, torrents and hydraulic sediment diversion structures. The measurements support the evaluation of bedload continuity across hydropower plants or other hydraulic structures.
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The discharge formula for (b):
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<math>Q=q*\frac{c_1}{c_2}</math>
  
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The BMS consists of two passive acoustic sensors, i.e. a geophone (GS-20DX manufactured by Geospace Technologies, Houston TX, USA) and an accelerometer (ICP352C03 manufactured by PCB Piezoelectronics, Depew NY, USA), mounted to an impact plate in a watertight housing (Figure 1a). These sensors do not directly measure bedload transport but register the vibration signals of the impact plate, i.e. oscillations induced by the impingement of passing bedload particles. In the case study HPP, the impact plate is the steel wall of the vortex tube (Figure 1a). The vibration signal output of both sensors is a voltage that is sampled at a frequency of fs = 51.2 kHz. The raw signals are then transmitted and further processed (Figure 1b, c).  
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being <math>{c_1}</math>  the tracer concentration in the injection, ''q'' the constant injection flow for the tracer (e.g. using a Mariotte device) and <math>{c_2}</math>  the tracer concentration at the downstream point.
  
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The BMS presented here is similar to the Swiss Plate Geophone System (SPGS) (Rickenmann et al. 2012) but includes an additional accelerometer sensor to expand the range of frequencies and hence the potentially detectable particle sizes compared to the SPGS.
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The tracer choice  depends on several factors:  chemical characteristics of the water, suspended sediment, distance between the injection and measuring section, type of flow to be measured, sensitivity of the tracer measurement devices and possible environmental impact of the tracer. Common tracers used: chemical (NaCl, NaI, NH4Cl) and fluorescent (fluorescein and Rhodamine WT).
  
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The maximum amplitude recorded during a bedload transport event can be related to the maximum grain diameter. Additionally, the sum of impulse counts above a certain amplitude threshold can be related to the transported bedload volume. Both relations are BMS setup- and site-dependent and therefore, a calibration is required to correlate the recorded impact signals to known bedload transport rates, often obtained from traditional bedload sampling (Rickenmann et al. 2012). If possible, a calibration in a laboratory flume as well as in the field setting is recommended (Gray et al. 2010, Rickenmann et al. 2014, Wyss et al. 2016a, Wyss et al. 2016b, Albayrak et al. 2017).
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It is important to comply with some conditions: the tracer cannot be absorbed and the solution must be well mixed. Emphasizing the last one, it is necessary to assure a good mixing length, which is the distance between the injection and measure sections, ensuring a stable concentration of the diluted tracer.
  
 
=Application=
 
=Application=
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Within the scope of FIThydro, a BMS consisting of a geophone and accelerometer was installed on the vortex tube at HPP Schiffmühle, which diverts bedload from the headwater channel to the residual flow reach. The vortex tube consists of a steel tube embedded in the side weir, connecting the two parallel channels (Figure 2). A gate valve is positioned in the side weir, which opens automatically when a predefined discharge is exceeded. The opening of the valve automatically triggers the BMS measurements.
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This method has been used for Itagra.ct to measure discharge into the fishways (Bravo-Córdoba y Sanz-Ronda, 2011; Fuentes-Pérez et al., 2016 and 2017; Sanz-Ronda et al., 2016; Bravo-Córdoba et al., 2018). One of the main aims was to improve the accuracy of the discharge coefficients related to technical fishways into the field. A continuous method, using Rodamine WT as a tracer and a portable fluorometer to measure the fluorescence of the samples,was applied (Figure 1 and 2).
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In contrast to the SPGS, the steel tube is used as an impact plate for the BMS and the sensors are mounted directly onto the outside of the steel tube (Figure 3). Therefore, laboratory calibration was not easily possible. Instead, the system was calibrated in the field by repeatedly dumping sediment samples of known grain size distribution and volume upstream of the vortex tube and subsequently flushing them to the residual flow reach. In addition, drop tests with single grains were performed when the vortex tube was not in operation. The single grain signals help to analyze the influence of grain size, grain form, drop height, and drop location on the amplitude and frequency signals.
 
  
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The first results of the presented BMS are promising, but the data analysis will be further refined and extended. Furthermore, a larger number of recorded flood events is necessary to check the plausibility of the results obtained so far. Overall, it is demonstrated that the measurement principle of the state-of-the-art SPGS can be extended to non-standardized impact plates like steel vortex tubes, and the use of an additional accelerometer sensor, given that appropriate calibration measures are taken.
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=Relevant mitigation measures and test cases=
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{{Suitable measures for Dilution gauging}}
  
 
=Other information=
 
=Other information=
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The total costs for the geophone and accelerometer sensors amount to approx. 885-1'330 €. The costs for the field computer, the analog-digital-converter, and the 3G modem are approx. 5'300-6'200 €. Additional costs for the installation, data transmission, and the calibration depending on the site conditions and set-up.
 
  
 
=Relevant literature=
 
=Relevant literature=
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*Albayrak, I., Müller-Hagmann, M., Boes, R.M. (2017). Calibration of Swiss Plate Geophone System for bedload monitoring in a sediment bypass tunnel. In Proc. 2nd Intl. Workshop on Sediment Bypass Tunnels (Sumi, T., ed.), paper FP16, Kyoto University, Kyoto, Japan
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*ISO 9555:1994. Measurement of liquid flow in open channels — Tracer dilution methods for the measurement of steady flow
  
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*Gray, J.R., Laronne, J.B., Marr, J.D.G. (2010). Bedload-surrogate Monitoring Technologies, US Geological Survey Scientific Investigations Report 2010-5091. US Geological Survey: Reston VA.
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*Tazioli, A. (2011). Experimental methods for river discharge measurements: Comparison among tracers and current meter. Hydrological Sciences Journal – Journal des Sciences Hydrologiques. 56. 1314-1324.  
  
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*Rickenmann, D., Turowski, J.M., Fritschi, B., Klaiber, A., Ludwig, A. (2012). Bedload transport measurements at the Erlenbach stream with geophones and automated basket samplers. Earth Surface Processes and Landforms, 37, 1000-1011.
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*Bravo‐Córdoba FJ, Sanz‐Ronda FJ. 2011. Evaluación de la eficiencia biológica de una escala de hendiduras verticales para la trucha autóctona (Salmo trutta L.) en la Cuenca del Duero. Master’s thesis. University of Valladolid, Spain.
  
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*Rickenmann, D., Turowski, J.M., Fritschi, B., Wyss, C., Laronne, J., Barzilai, R., Reid, I., Kreisler, A., Aigner, J., Seitz, H., Habersack, H. (2014). Bedload transport measurements with impact plate geophones: comparison of sensor calibration in different gravel-bed streams. Earth Surface Processes and Landforms, 39, 928-942.
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*Bravo‐Córdoba FJ, Sanz‐Ronda FJ, Ruiz‐Legazpi J, Celestino LF, Makrakis S. 2018. Fishway with two entrance branches: Understanding its performance for potamodromous Mediterranean barbels. Fisheries Management and Ecology 25(1): 12–21.
  
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*Wyss, C.R., Rickenmann, D., Fritschi, B., Turowski, J.M, Weitbrecht, V., Boes, R.M. (2016a). Laboratory flume experiments with the Swiss plate geophone bed load monitoring system: 1. Impulse counts and particle size identification. Water Resources Research, 52, 7744-7759.
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*Fuentes-Pérez JF, Sanz-Ronda FJ, Martínez de Azagra-Paredes A, García-Vega A, Martínez de Azagra A, García-Vega A. 2016. Nonuniform hydraulic behavior of pool-weir fishways: a tool to optimize its design and performance. Ecol Eng 86: 5–12.
  
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*Wyss, C.R., Rickenmann, D., Fritschi, B., Turowski, J.M, Weitbrecht, V., Boes, R.M. (2016b). Laboratory flume experiments with the Swiss plate geophone bed load monitoring system: 2. Application to field sites with direct bed load samples. Water Resources Research, 52, 7760-7778.
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*Fuentes-Pérez JF, García-Vega A, Sanz-Ronda FJ, Martínez de Azagra Paredes A. 2017. Villemonte’s approach: a general method for modelling uniform and non-uniform performance in stepped fishways. Knowl. Manag. Aquat. Ecosyst., 418, 23.
  
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*Sanz-Ronda FJ, Bravo-Córdoba FJ, Fuentes-Pérez JF, Castro-Santos T. 2016. Ascent ability of brown trout, Salmo trutta, and two Iberian cyprinids− Iberian barbel, Luciobarbus bocagei, and northern straight-mouth nase, Pseudochondrostoma duriense− in a vertical slot fishway. Knowledge and Management of Aquatic Ecosystems (417): 10.
  
 
=Contact information=
 
=Contact information=

Latest revision as of 15:25, 11 April 2020

Quick summary

Figure 1: Dilution gauging in a fishway: making the dilution of the tracer (Rhodamine Wt) (source: Itagra.ct).
Figure 2: Dilution gauging in a fishway: Mariotte device for continuous injection into the fishway (source: Itagra.ct).

Developed by:Francisco Javier Bravo, Itagra.ct

Date:

Type: Method

Introduction

This method requires the release of a known tracer concentration in a section of the river or fishway and the subsequent determination of the tracer concentration in a downstream section. It is based on the dilution relationships between the injection of the tracer and the discharge we want to know. There are two main different methods for the injection of the tracers into the flow: (a) instantaneous or integration method and (b) continuous method.

The discharge for (a) is calculated as:

being the tracer concentration which is introduced in the watercourse with discharge Q. c is the concentration of the sample in volume V and T is equal to the time needed for the tracer to be transported downstream.

The discharge formula for (b):

being the tracer concentration in the injection, q the constant injection flow for the tracer (e.g. using a Mariotte device) and the tracer concentration at the downstream point.

The tracer choice depends on several factors: chemical characteristics of the water, suspended sediment, distance between the injection and measuring section, type of flow to be measured, sensitivity of the tracer measurement devices and possible environmental impact of the tracer. Common tracers used: chemical (NaCl, NaI, NH4Cl) and fluorescent (fluorescein and Rhodamine WT).

It is important to comply with some conditions: the tracer cannot be absorbed and the solution must be well mixed. Emphasizing the last one, it is necessary to assure a good mixing length, which is the distance between the injection and measure sections, ensuring a stable concentration of the diluted tracer.

Application

This method has been used for Itagra.ct to measure discharge into the fishways (Bravo-Córdoba y Sanz-Ronda, 2011; Fuentes-Pérez et al., 2016 and 2017; Sanz-Ronda et al., 2016; Bravo-Córdoba et al., 2018). One of the main aims was to improve the accuracy of the discharge coefficients related to technical fishways into the field. A continuous method, using Rodamine WT as a tracer and a portable fluorometer to measure the fluorescence of the samples,was applied (Figure 1 and 2).

Relevant mitigation measures and test cases

Relevant measures
Baffle fishways
Fish lifts, screws, locks, and others
Fishways for eels and lampreys
Nature-like fishways
Operational measures (turbine operations, spillway passage)
Pool-type fishways
Vertical slot fishways
Relevant test cases Applied in test case?
Guma and Vadocondes test cases Yes

Other information

Relevant literature

  • ISO 9555:1994. Measurement of liquid flow in open channels — Tracer dilution methods for the measurement of steady flow
  • Tazioli, A. (2011). Experimental methods for river discharge measurements: Comparison among tracers and current meter. Hydrological Sciences Journal – Journal des Sciences Hydrologiques. 56. 1314-1324.
  • Bravo‐Córdoba FJ, Sanz‐Ronda FJ. 2011. Evaluación de la eficiencia biológica de una escala de hendiduras verticales para la trucha autóctona (Salmo trutta L.) en la Cuenca del Duero. Master’s thesis. University of Valladolid, Spain.
  • Bravo‐Córdoba FJ, Sanz‐Ronda FJ, Ruiz‐Legazpi J, Celestino LF, Makrakis S. 2018. Fishway with two entrance branches: Understanding its performance for potamodromous Mediterranean barbels. Fisheries Management and Ecology 25(1): 12–21.
  • Fuentes-Pérez JF, Sanz-Ronda FJ, Martínez de Azagra-Paredes A, García-Vega A, Martínez de Azagra A, García-Vega A. 2016. Nonuniform hydraulic behavior of pool-weir fishways: a tool to optimize its design and performance. Ecol Eng 86: 5–12.
  • Fuentes-Pérez JF, García-Vega A, Sanz-Ronda FJ, Martínez de Azagra Paredes A. 2017. Villemonte’s approach: a general method for modelling uniform and non-uniform performance in stepped fishways. Knowl. Manag. Aquat. Ecosyst., 418, 23.
  • Sanz-Ronda FJ, Bravo-Córdoba FJ, Fuentes-Pérez JF, Castro-Santos T. 2016. Ascent ability of brown trout, Salmo trutta, and two Iberian cyprinids− Iberian barbel, Luciobarbus bocagei, and northern straight-mouth nase, Pseudochondrostoma duriense− in a vertical slot fishway. Knowledge and Management of Aquatic Ecosystems (417): 10.

Contact information

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