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Acoustic Doppler Profiler
• Used to:• Measure Velocity, depth & calculate flow (Q)• During floods when gauging weirs fail• To verify a gauging structure’s measurements
History
• Manual way (paper, measuring tape, stopwatch): Velocity= • Then: Flow (Q)= Area x Velocity• Mechanical propeller
Acoustic Doppler Profiler
Velocity of
source
Emitted wave Velocity
of receiver
Observed wave
Left Bank Right BankDirection of movement
Components• Boat• Transducer (SonTek M9)
• PCM (Base station for power)• GPS System• Laptop• Computer programme (River Survey)• Communication
• Direct connection (cable)• Bluetooth (200m)• Spread spectrum (2km)
Measuring Procedure• Set the programme• Calibrate compass• Minimum of 3 people
• 2 in river• 1 on laptop
• Remember: 1 accurate reading = 4 Transects• NB: Velocity of the boat < velocity of water
Site selection
• There should be no:• Bends• Rocks• Vegetation on river bed• Clear water• Uniform flow
Gauging Weirs
• Used to get the stage:• Stage is height of water above low notch (crest)• Stage is then used in Discharge Table to get the Flow (Q)
ComponentsUpstream gauge plate
Downstream gauge plate
Hydraulic jumpand
Super critical flow
Clear pool lengthAnd
Sub-critical flow
Formulas for Design (Crump Weir)
• Froude number: Fr=• Energy Head: H= h + (Bernoulli's formula)• Gauge plate position: 2 x Hd (upstream) & 10 x (Hd + Z)
(downstream)• Flow: Q = 1.981 x b x H1,5
• Pool characteristics:• Minimum Length: 5 x length of structure• Minimum Depth:
Site selection• Longitudinal Section• Easy Access• Straight• Froude number (subcritical flow)• Pool length• Width of river• Vegetation in water• Obstructions (Down stream)
• No swamps or wetlands• No dumping sites nearby
Maintenance• Remove debris & island (upstream and downstream)• Remove vegetation growth• Clean Gauge plate
Gauge Plate (Parent)• Metal plate (1m long & 300mm wide)• Used to measure the stage• Invert level = crest of structure (low-notch)• Placed against a structure or as a stand alone• Must be cleaned or replaced when dirty• Used to calibrate instruments and double check their
readings• Position: use formula depending on structure (e.g. 2 x Hd for
upstream)
Type X
• Float and counter-weight method• Records on a chat (graph)• Heavy maintenance
• Changing of chats (every two weeks)• Tracing data into computer
• Not effecting in high siltation sites
Thalimedes
• Manufactured by OTT• Replacement of the TypeX• Float and counter-weight• Uses a shaft encoder• Stores electronically
• Stores for 8 months (then starts to over write)
Position of Inlet pipe• Must be inline with gauge plate, centre of the pipe crown must be at invert of plate.
STS pressure transducer• Works on the pressure principle• Has two parts:
• A sensor part (with diaphragm)• Has ranges from 0-4m up to 0-100m
• Logger part• Uses a signal of 4 – 20mA (so is be supplied by Alkaline batteries)• Needs a laptop/PDA to retrieve data
Loggers
• Data Collection Platform (looks like an electric circuit)• Power supply
• Battery (12v)• Solar panel
• Kept clean• Protect from vandalism
• Power regulator• Surge protection• GSM/GPRS communication• Logger (Logo Sens/Dou Sens)
Weather station
• Help estimate water inflow (precipitation)• Rain gauge (Tipping Bucket)• Anemometer (Wind speed & direction)• Barometer ( Atmospheric pressure)• Viewing screen
Basic tools to take along
• Keys for the recorder hut• Inspection form• Camera (to take pictures of damages)• Laptop/PDA & DouLink cable• Multi meter (to check power for DCP)
• For STS pressure transducers laptop will show the remaining power