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Module 10/11 Stream Surveys

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

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  1. Module 10/11Stream Surveys Stream Surveys – February 2004 Part 3 – Hydrologic Assessment

  2. 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. • explain the stage-discharge relationship.

  3. Stream assessments • Water quality • Habitat • Hydrologic • Biological • Watershed

  4. Hydrologic assessments

  5. Stream Hydrology • Velocity • Discharge (flow) • Stage-discharge relationship

  6. USGS Velocity • The rate which the flow travels along the channel reach. • Measured in feet per second or meters per second

  7. Velocity – Current Meters • Propeller type meters • Electromagnetic meters using waves to measure velocity • (e.g. March-McBirney).

  8. 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)

  9. 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

  10. 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.

  11. 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

  12. 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

  13. 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"

  14. Ultrasonic depth sensor NRRI Stage (Depth) Measurement Devices • Non-recording staff gage • Float sensors • Ultrasonic sensors • Pressure transducers Pressure transducer Staff gages (Forestry Suppliers)

  15. Stage-Discharge Relationship • Compute discharge at a range of stages • Plot depth vs flow and fit a curve

  16. Importance of flow/discharge in determining loading • Slide to be completed by 3/31/04

  17. Stream surveys - references • Techniques of Water-Resources Investigations Reports • http://water.usgs.gov/pubs/twri/ • National Field Manual for the Collection of Water-Quality Data • http://water.usgs.gov/owq/FieldManual/ • Rapid bioassessment protocols for wadeable streams • http://www.epa.gov/owow/monitoring/rbp/

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