FLOW CALIBRATION OF THE BRYAN

CANAL RADIAL GATE AT THE UNITED

IRRIGATION DISTRICT

USCID Water Management Conference

Meeting Irrigation Demands in a Water-Challenged Environment

SCADA and Technology: Tools to Improve Production

Fort Collins, Colorado September 28 - October 1, 2010

Gabriele Bonaiti

Eric Leigh

Askar Karimov Extension Associates

Guy Fipps

Professor and Director

Irrigation Technology Center

Texas AgriLife Extension Service

Department of Biological and Agricultural Engineering

Texas A&M University, College Station

Project based upon work supported by the Cooperative State Research,

Education, and Extension Service, U.S. Department of Agriculture, under

Agreement No. 2005‐45048‐03208

For program information, see http://riogrande.tamu.edu

LOWER RIO GRANDE VALLEY, TEXAS

UNITED I.D.

37,800 acres

47% urban expansion

57,000 acre-feet Class A water rights

50 miles open canals, 115 miles of gravity fed pipeline

Bryan canal

carries 30% of total water distributed: › Irrigation: 10,000 acre-

feet/yr

› Municipal: 23,000 acre-feet/yr

Mission

Mc Allen

DEMONSTRATION PROJECT

Purpose

Improve the efficiency of Bryan Canal management by:

› Replacing the old, dilapidated sliding gate

› Establishing telemetry and remote control capabilities

› Giving the District the ability to control the canal

system based on flow

DEMONSTRATION PROJECT

Objectives and issues related to gate

calibration for flow

Calibrate a locally manufactured radial gate for flow

Develop an easy to use set of procedures so the district

can calibrate their own gates

Determine best equation for local flow conditions

Determine how are choice of actuators affects the

process

Demonstrate the use of inexpensive data loggers (“non

SCADAPACK”) and other components

Replacing head vertical slide gate in poor condition…

Trapezoidal concrete-

lined canal

225 cfs

capacity

7 ft deep,

18 ft top

width, 4 ft

bottom width, side

slopes of

1:1

…with new radial gate

Advantages:

Small force for lift and operation,

Good hydraulic discharge for

calibrating a gate to serve as a flow measurement device

Rectangular structure

24 ft long and 10 ft

wide

Radius of 7 ft, vertical

height of 7 ft, pinion height of 3.5 ft.

Opening 0 - 5 ft

Gate leaf edges have

hard bar-shaped rubber seals

Equipment and Instrumentation

Pressure transducer sensors to measure water level

Actuator to control manually and remotely the gate opening

Doppler flow meter to measure flow

Calibration of a Doppler Flow Meter

Methods:

› Price Type AA as current meter

› Tests were carried out at high and low flows

› USGS recommended procedures using the two-point

method

Results:

› Doppler max. flow = 116 cfs (1.7 ft/s)

› Doppler average flow < current meter flow by 3%

Doppler data were corrected accordingly

Calibration of Vertical Gate Opening vs Actuator

Position and Input Voltage

Methods

› 4-20 mA input to the actuator was set to a 0-100%

scale, which corresponds to 0 to 5’ gate opening

› Measurements were taken every 0.5’during:

opening of gate

closing of gate

› Measurements:

vertical opening of the gate

position of actuator

Hysteresis: “from the Greek for

shortcoming, to be late, to fall short…”

Results: Hysteresis between Actuator position and Gate opening

y = 0.0176x2 + 0.9057x - 0.029

R² = 0.9996

y = 0.0328x2 + 0.8389x - 0.0352

R² = 0.9999

0

1

2

3

4

5

0 1 2 3 4 5

Ga

te o

pen

ing

(ft

)

Actuator position (ft)

Opening motion

Closing motion

Two different equations were used to convert actuator signal into gate

opening

R² = 0.9996

R² = 0.9999

0

1

0 1

Ga

te o

pen

ing

(ft)

Actuator position (ft)

Opening motion

Closing motion

0.1 ft

difference =

4.4 cfs in

average

Results: Hysteresis between Data logger input and Actuator position

Disregarded data logger input data for flow calibration purposes

y = 0.0128x2 + 0.9535x - 0.0133

R² = 0.9998

y = -0.0146x2 + 1.0888x + 0.056

R² = 0.9998

0

1

2

3

4

5

0 1 2 3 4 5

Actu

ato

r p

osi

tion

(ft

)

Data logger input (ft)

Opening motion

Closing motion

0.16 ft

difference =

7.1 cfs in

average

Calculated vs Measured Flow Rate

Measured data

0

10

20

30

40

50

60

70

0

1

2

3

4

5

6

7

01/12/09 02/09/09 03/09/09

Flo

w (

cfs)

Fee

t (f

t)

Upstream level Downstream level

Gate opening Measured flow

Range in conditions that were observed

› Flow conditions were always submerged

Parameter Max Average Min

Opening (ft) a 1.5 0.5 0.0

Upstream level (ft) h1 7.0 5.4 3.9

Downstream level (ft) h2 5.4 4.2 2.2

Head differential(ft) h1-h2 2.8 1.2 0.0

Calculating Flow › submerged flow orifice equation

Q = discharge Cq = discharge coefficient a = gate opening L = gate width g = gravitational constant h1 = upstream level h2 = downstream level h1 - h2 = head differential

› This equation is commonly used to calculate flow through an underflow gate for slow and very submerged flow

Values were selected for Cq

until the calculated cumulative flow converged with measured cumulative flow

Results: A single discharge coefficient Cq = 0.70

matched measured flow with an average error of

2.9 % (relative standard deviation calculated when flow > 2 cfs)

0

600

1,200

1,800

2,400

3,000

3,600

4,200

0

10

20

30

40

50

60

70

01/12/09 02/09/09 03/09/09

Cu

mu

late

d flo

w (ac

ft)

Flo

w (cf

s), R

el. s

t. d

ev. (

%)

Calculated flow Measured flow Relative standard deviation

Results: Linear regression interpolating all events

y = 1.0197x - 0.513

R² = 0.9943

-10

10

30

50

70

-10 10 30 50 70

Cal

cula

ted flo

w (cf

s)

Measured flow (cfs)

Results: Effects of correction with hysteresis

Results: effects of correction with hysteresis

The linear regressions

fitting the two groups of

data were tested for

parallelism, and the

slopes resulted

statistically different

from each other

CONCLUSIONS

It was possible to calibrate a locally manufactured

gate for flow

The doppler flow meter was useful as the reference

flow because of high accuracy and large amount

of data that was processed

Further work:

› Test the submerged orifice equation in different conditions

of flow

› Test other equations

› Apply the same procedure to other gates

› Test different actuator types and data logger set up to

limit hysteresis issues