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Module 10/11 Stream Surveys. Stream Surveys – February 2004 Part 3 – Hydrologic Assessment. Objectives. Students will be able to: define velocity in a stream. identify methods used to determine velocity. define stream discharge. describe methods used to determine stream discharge.

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module 10 11 stream surveys

Module 10/11Stream Surveys

Stream Surveys – February 2004

Part 3 – Hydrologic Assessment


Students will be able to:

  • define velocity in a stream.
  • identify methods used to determine velocity.
  • define stream discharge.
  • describe methods used to determine stream discharge.
  • explain the stage-discharge relationship.
stream assessments
Stream assessments
  • Water quality
  • Habitat
  • Hydrologic
  • Biological
  • Watershed
stream hydrology
Stream Hydrology
  • Velocity
  • Discharge (flow)
  • Stage-discharge relationship


  • The rate which the flow travels along the channel reach.
  • Measured in feet per second or meters per second
velocity current meters
Velocity – Current Meters
  • Propeller type meters
  • Electromagnetic meters using waves to measure velocity
    • (e.g. March-McBirney).
velocity in stream sensors

SonTek (YSI)

Velocity – in stream sensors
  • Useful for long-term velocity measurement in one place
  • Not for use in discharge determination

Bubbler flow sensor (Campbell Scientific)

velocity determination float method
Velocity determination: Float Method
  • Inexpensive and simple
  • Measures surface velocity
  • Mean velocity obtained using a correction factor
  • Basic idea: measure the time that it takes an object to float a specified distance downstream
stream discharge
Stream Discharge
  • The volume of water passing through the cross-sectional area of the channel per unit time
  • Average velocity of the water, in meters/sec, multiplied by the cross-sectional area of stream at that point, in square meters.
stream discharge measurement setup
Stream Discharge Measurement: Setup
  • Stretch tape across river at right angle to direction of flow
  • Choose measurement intervals
    • 10 interval mininum
  • Width of the subsections can be variable across the cross-section.
  • No more than 10% of expected discharge per interval
  • No interval more than 3 meters wide
stream discharge measurement setup1
Stream Discharge Measurement: Setup
  • At each point – measure velocity with meter at either 0.6 d or 0.2 and 0.8 d
  • Note: Point velocity is constantly changing (pulsation) – average over time
  • Operator position should NOT affect flow pattern near flow meter – downstream of meter, at arms length
stage discharge relationship
Stage-Discharge Relationship
  • Discharge measurements are made at various stages to define the relation between stage and discharge
    • stage is the height of the water surface above an established datum plane.
  • Water-surface elevation called the "gage height"
stage depth measurement devices

Ultrasonic depth sensor


Stage (Depth) Measurement Devices
  • Non-recording staff gage
  • Float sensors
  • Ultrasonic sensors
  • Pressure transducers

Pressure transducer

Staff gages (Forestry Suppliers)

stage discharge relationship1
Stage-Discharge Relationship
  • Compute discharge at a range of stages
  • Plot depth vs flow and fit a curve
stream surveys references
Stream surveys - references
  • Techniques of Water-Resources Investigations Reports
  • National Field Manual for the Collection of Water-Quality Data
  • Rapid bioassessment protocols for wadeable streams