IMPROVING FLOW MEASUREMENT AND EFFICIENT

DELIVERY TO YOUR FIELD

ZACK LIBBIN, MSCE, PE

DISTRICT ENGINEER

ELEPHANT BUTTE IRRIGATION DISTRICT

OBJECTIVES / TAKE AWAYS

• PURPOSE AND BENEFITS OF METERING

• HOW DELIVERY CAN BE IMPROVED FOR INCREASED IRRIGATION EFFICIENCY

• OPEN DITCH FLOW IMPROVEMENTS

• OPEN DITCH METERING METHODS

PURPOSE OF METERING

CANT MANAGE IT IF YOU CAN MEASURE IT

QUANTIFY IMPROVEMENTS

IDENTIFY PROBLEMS

VERIFICATION

IMPROVING EFFICIENCIES

WELL METERING

• REQUIRED IN LRG

• EVALUATE PERFORMANCE

• PART OF DETERMINING EFFICIENCIES

• MONITORING EFFICIENCIES

• IDENTIFY PROBLEMS

WHAT IMPROVED IRRIGATION EFFICIENCY LOOKS LIKE

• LESS WATER REQUIRED FOR THE SAME BENEFIT = WATER CONSERVATION

• REDUCED DEEP PERCOLATION BELOW OR AWAY FROM ROOT ZONE

• REDUCED COSTS

Deep percolation

Deficit

Root zone /Usable water

𝐼𝑟𝑟𝑖𝑔𝑎𝑡𝑖𝑜𝑛 𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 =𝑡𝑜𝑡𝑎𝑙 𝑤𝑎𝑡𝑒𝑟 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑

𝑤𝑎𝑡𝑒𝑟 𝑑𝑒𝑙𝑖𝑣𝑒𝑟𝑒𝑑 𝑡𝑜 𝑟𝑜𝑜𝑡 𝑧𝑜𝑛𝑒 𝑓𝑜𝑟 𝐸𝑇 𝑛𝑒𝑒𝑑𝑠

𝑒(%) =𝑒𝑐 ∗ 𝑒𝑎

100Where e = overall irrigation efficiency

ec= conveyance efficiency

ea= field application efficiency

IMPROVING IRRIGATION EFFICIENCY

• IRRIGATION TECHNIQUES

• BORDER-BASIN SURFACE IRRIGATION SYSTEMS CAN BE EFFICIENT

• LESS SEEPAGE PRIOR TO/DURING DELIVERY

• LEVEL FIELD/CORRECT SLOPE FOR YOUR SOIL TYPE

• FASTER IRRIGATION/REDUCED ADVANCE TIME

• UNIFORM APPLICATION

• REDUCED SURFACE EVAPORATION

• ELIMINATE RUNOFF

• SMALLER BLOCKS

• ET BASED SCHEDULING

IMPROVING CONVEYANCE EFFICIENCY TO YOUR FIELD

• A CLEAN UNIFORM DITCH

• LINED OR PIPED DITCH

• ADEQUATE FLOW

• CORRECTLY SIZED CANAL TURNOUT

• ADEQUATE PUMP(S)

• HIGH FLOW FIELD TURNOUT

• ADEQUATE DITCH CAPACITY

• EVALUATE RESTRICTIONS

• PRESSURIZE?

BENEFITS TO IMPROVING A DITCH

• REDUCE SEEPAGE PRIOR TO DELIVERY

• REDUCED EVAPORATION

• LESS MAINTENANCE?

• IMPROVED FLOW

• IMPROVED HEAD

• LESS DITCH BREAKS

METERING YOUR DITCH

• WEIRS

• FLUMES

• DIRECT VELOCITY MEASUREMENT

• CIRCULAR GATE

• FACTORS TO CONSIDER

• DESIGN FLOW/CAPACITY

• RANGE OF FLOW

• COST

• ACCEPTABLE HEADLOSS

• SUBMERGENCE

• MAINTENANCE

• CONSTRUCTION AND INSTALLATION

METERING YOUR DITCH - WEIRS

• BROAD CRESTED

• SHARP CRESTED

• V-NOTCH

MEASUREMENT IS MADE BY OBSERVING OR

RECORDING AN UPSTREAM HEAD/DEPTH

• PROS

• EASY TO DESIGN

• EASY TO CONSTRUCT

• EASY TO READ

• LOW COST

• CONS

• REQUIRES A RELATIVELY HIGH HEADLOSS

• NOT SELF CLEANING OR SELF DRAINING

• ACCURACY CAN BE EFFECTED BY APPROACH

VELOCITY

𝑄 = 𝑐𝑑 ∗ tan∅

2∗ 𝐻

52

Where Q = flow

Cd= discharge coefficient

L = length of weir

H = measured upstream head

∅= V notch weir angle

𝑄 = 𝑐𝑑 ∗ 𝐿 ∗ 𝐻32

𝑄 =2

3∗ 𝑐𝑑 ∗ 2𝑔 ∗ 𝐿 ∗ 𝐻

32

Photo credits: openchannelflow.com

METERING YOUR DITCH -FLUMES

• LONG THROATED

• RAMP

• WIN-FLUME

• SHORT THROATED

• CUTTHROAT

• SAMANI

• PARSHALL

• PROS

• EASY TO DESIGN

• EASY TO READ

• SOME ARE SELF CLEANING

• RELATIVELY LOW HEADLOSS

• CAN BE PORTABLE

• CONS

• HIGHER COST

• SIGNIFICANT MATERIALS TO CONSTRUCT

• MODERATELY DIFFICULT TO CONSTRUCT AND

INSTALL

𝑄 = 𝑐𝑑 ∗ ℎ𝑛

Where Q = flow

Cd= discharge coefficient

H = measured upstream head

n = flume design exponent

METERING YOUR DITCH – SAMANI FLUMES

THREE SIMPLE FLUMES FOR FLOW MEASUREMENT:

SAMANI, Z., (2017). “THREE SIMPLE FLUMES FOR FLOW MEASUREMENT IN OPEN CHANNELS.” J. IRRIG. DRAIN.

ENG., 10.1061/(ASCE)IR.1943-4774.0001168#STHASH.CPGVVTI0.DPUF

HTTP://ASCELIBRARY.ORG/DOI/ABS/10.1061/%28ASCE%29IR.1943-4774.0001168

• RECTANGULAR (1)

(S-M FLUME)

• TRAPEZOIDAL (2)

• CIRCULAR (3)

(1)(2) (3)

REFERENCES AND ACKNOWLEDGEMENTS

• SAMANI, Z., (2017). “THREE SIMPLE FLUMES FOR FLOW MEASUREMENT IN OPEN CHANNELS.” J. IRRIG. DRAIN.

ENG., 10.1061/(ASCE)IR.1943-4774.0001168#STHASH.CPGVVTI0.DPUF

• BUREAU OF RECLAMATION, 2001. WATER MEASUREMENT MANUAL. 3RD ED., REVISED REPRINT, U.S. GOVERNMENT PRINTING OFFICE,

WASHINGTON DC, 20402

• SAMANI, Z., AND MAGALLANEZ, H. (1993). “MEASURING WATER IN TRAPEZOIDAL CANALS.” J. IRRIG. DRAIN.

ENG., 10.1061/(ASCE)0733-9437(1993)119:1(181), 181–186.

• SAMANI, Z., AND MAGALLANEZ, H. (2000). “SIMPLE FLUME FOR FLOW MEASUREMENT IN OPEN CHANNEL.” J. IRRIG. DRAIN.

ENG., 10.1061/(ASCE)0733-9437(2000)126:2(127), 127–129.

• - SEE MORE AT: HTTP://ASCELIBRARY.ORG/DOI/ABS/10.1061/%28ASCE%29IR.1943-4774.0001168#STHASH.CPGVVTI0.DPUF

• CLEMMENS, A.J.; WAHL T.L.; BOS, M.G., AND REPLOGLE, J.A. 2001.

WATER MEASUREMENT WITH FLUMES AND WEIRS. ILRI PUBLICATION 58.

• PHOTOS:

• PATRICK LOPEZ, EBID

• HENRY MAGALLANEZ

• ZOHRAB SAMANI

• OPEN CHANNEL FLOW.COM BLOG: HTTP://WWW.OPENCHANNELFLOW.COM/BLOG/WEIR-PLATE-MATERIALS, RETRIEVED 2017