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