Improved Water Resource Management Using an Acoustic Pulsed Doppler Sensor in a Shallow Open Channel

MIKE COOK, PHD

Irrigation AustraliaJuly - 2012

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Background

• Less than 1% of freshwater worldwide is accessible to humans

- Climate change, drought - Water scarcity

• Agriculture represents 70% of freshwater use - Efficient use essential for ag production & water savings - Irrigation upgrades – flow matters - Flow data is often “good enough”

• Many governments are mandating flow monitoring - Australia Bureau of Meteorology - California Water Resources Act

• Accurately measuring flow is increasingly important

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Development Goals

• Understand shallow and complex flow- Turnout or irrigation ditch

• Leverage SonTek expertise in pulsed Doppler technology

- Better measurement for end users• Reduce high cost of instrument hardware

– Including installation with minimal or no earthworks

• An accurate flow measurement- International requirements (Australia and California)- Better delivery information – save water

• Work in as shallow water as possible- Low flows add up over time

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Development – Data Collection

Phase 1 of SBIR from the USDA

•More than 100 FlowTracker measurements in small channels- Understand complex flow conditions- In many cases more than 100 points- Isovel maps

•Data used to determine- Beam angles- Proprietary flow algorithms

Disclaimer: This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 2008-33610-19458.  Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the U.S. Department of Agriculture

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Development – Hardware

Phase 2 of SBIR

• Relies on Pulsed-Doppler technique using timing

controllers to profile water velocity in discrete layers

• Newly developed High Definition feature can profile cells 2

cm apart (SmartPulseHD)

• Low profile designed to operate in 8 cm of water

• Beam geometry selected based on Phase I work

• Profiles the vertical and horizontal distribution of velocities

• Flow tested against known USGS ratings

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End Product – SonTek IQ

• Bottom mounted / up-looking pulsed Doppler profiler (3MHz)- Measures water level- Measures water velocity

Calculates flow and total volume- Measure temperature

• Adaptive velocity sampling via SmartPulseHD

• Communications via RS232, SDI-12, Modbus• External power source 8-15 VDC• Developed with a grant from the USDA and significant feedback from California Polytechnic University and the University of Illinois

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SonTek IQ Attributes

Skew Beam

Skew Beam

Along Axis Beam (upstream)

Along Axis Beam (downstream)

• Velocity profiling beams (4) – 3MHz - Along axis beams (2), 25° off vertical axis

Profiles velocity along channel axis

- Skew beams (2), 60° off vertical axis & 60° off center axisProfiles velocity in shallow water and off central axis

Profiles the horizontal and vertical distribution of velocities

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SonTek IQ Attributes

Temperature Sensor

Water Level Measurement - Vertical Beam - Pressure Sensor (flow through cell)

•Water level measured by vertical beam and pressure sensor

- Work in tandem to provide best possible water level data

- Calculates cross-sectional area of flow from area rating

• High resolution temperature sensor

- Provides data for speed of sound correction

- More accurate velocity = more accurate flow data

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SonTek IQ Attributes

Mounting Bracket

Power and Communications connector

• Five conductor cable (connector not wet mateable) - Communications: RS232, SDI12, ModBus - Power requirements: 8 - 15 VDC• Mounting brackets - Allows for easy installation, two screws 5" (12.7 cm) apart - Additional options for mounting - underside of the instrument (3- brass inserts)

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Multi-beam profiling with SmartPulseHD

•Multiple profiling beams sample more or the water–Maps horizontal and vertical distribution of velocities

•Adaptively samples velocity using three acoustic techniques–Pulse coherent, Pulse incoherent and Broadband

•Selects acoustic technique based on:–Water depth–Water Velocity–Turbulence

•Benefit for end-users–Reduces noise in the data–Provides best possible flow data

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SonTek IQ Data – Velocity Profile

IQ SmartPulseHD Technology30 Second Average

Velocity profiles below are the same test facility in similar flow conditions – more data & less noise = better measurement

Older Doppler Technology60 Second Average

1 1.2 1.4 1.6 1.8 2 2.20

0.5

1

1.5

2

2.5

Velocity (ft/s)

Dep

th (

ft)

0.8 1 1.2 1.4 1.6 1.8 20

0.5

1

1.5

2

2.5

Velocity (ft/s)

Dep

th (

ft)

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Application/Concept

The SonTek IQ minimizes earthworks – in many cases decision makers are building a section for a magmeter or installing a control section made of concrete (weirs, ramp flumes, etc.).

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Cocopah Test Site

• Site near Yuma, AZ– Cooperation of USGS (Yuma)

• Upstream – culvert outlet (15m)• Downstream – ramp flume (10m)• IQ installed in trapezoidal canal

– Cleaned cross-section (important)– Custom mounting frame

• Comparison data– Rating curve (water level via radar)– FlowTracker measurements– Complex site due to backwater effect

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Cocopah Test Site – Instrument Configuration

• USGS uses water level as a surrogate for flow (radar) with periodic gagings (15/3)

• 5 minute Sampling interval, 3 minute Averaging interval

• IQ installed on custom railing, elevated from bottom (0.31 ft)

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Cocopah Test Data

1 2 3

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Cocopah Test Results

Water Level (ft)

IQ Flow (cfs)

Reference (cfs)

% Error

Comparison 1 1.89 13.84 13.48† 2.6

Comparison 2 2.12 17.80 18.49* -3.7

Comparison 3 2.06 16.48 16.85* -2.2

*FlowTracker comparison data†USGS Gage dataAverage error = -2.8%

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Ypsilanti Test Site Information

• Site near Winterhaven, AZ– Cooperation of USGS (Yuma)

• Upstream – culvert outlet (10m)• Downstream – broad crested weir (20m)• IQ installed just under walkway

– Traditionally a difficult site – Broad crested weir – small changes in level

means large changes in flow– Cleaned cross-section (important)

• Comparison data– Rating curve (water level via bubbler)– FlowTracker measurements

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Ypsilanti Test Site – Instrument Configuration

– USGS uses water level as a surrogate for flow with periodic gagings (15/3)

– 3 minute Sampling interval, 3 minute Averaging interval

– IQ Installed with weighted mount, slightly raised

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Ypsilanti Test Data

1 2 3 4

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Ypsilanti Test Results

Water Level (ft)

IQ Flow (cfs)

Reference (cfs)

% Error

Comparison 1 1.81 18.73 19.01† 1.1

Comparison 2 1.58 8.36 8.45† 1.4

Comparison 3 1.90 23.85 24.33† 1.6

Comparison 4 2.19 43.70 43.25* 1.0

* FlowTracker comparison made measured 42.07 cfs Average error = 1.28%

† USGS gage data

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IQ Data Summary and Conclusions• SonTek-IQ was installed at traditional irrigation sites

– Compared to rating curves and discreet measurements– Sites were traditionally good for monitoring water level– Typically not ideal for a velocity sensors

• SonTek- IQ performance– Flow rate was within 2.8% at Cocopah– Flow rate was within 1.3% at Ypsilanti– Average error for the two sites was 1.9%– Better data means better decisions and save water

• Reliable data immediately after install– No indexing was required

• Velocity data is crucial for irrigation monitoring