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

Developed by: Richards, Reed, Ruzycki Updated: February 2004 U3-m10/11c-s2 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.

Developed by: Richards, Reed, Ruzycki Updated: February 2004 U3-m10/11c-s3 Stream assessments  Water quality  Habitat  Hydrologic  Biological  Watershed

Developed by: Richards, Reed, Ruzycki Updated: February 2004 U3-m10/11c-s4 Hydrologic assessments

Developed by: Richards, Reed, Ruzycki Updated: February 2004 U3-m10/11c-s5 Stream Hydrology  Velocity  Discharge (flow)  Stage-discharge relationship

Developed by: Richards, Reed, Ruzycki Updated: February 2004 U3-m10/11c-s6 Velocity USGS  The rate which the flow travels along the channel reach.  Measured in feet per second or meters per second

Developed by: Richards, Reed, Ruzycki Updated: February 2004 U3-m10/11c-s7 Velocity – Current Meters  Propeller type meters  Electromagnetic meters using waves to measure velocity  (e.g. March-McBirney).

Developed by: Richards, Reed, Ruzycki Updated: February 2004 U3-m10/11c-s8 Velocity – in stream sensors  Useful for long-term velocity measurement in one place  Not for use in discharge determination Bubbler flow sensor (Campbell Scientific) SonTek (YSI)

Developed by: Richards, Reed, Ruzycki Updated: February 2004 U3-m10/11c-s9 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

Developed by: Richards, Reed, Ruzycki Updated: February 2004 U3-m10/11c-s10 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.

Developed by: Richards, Reed, Ruzycki Updated: February 2004 U3-m10/11c-s11 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

Developed by: Richards, Reed, Ruzycki Updated: February 2004 U3-m10/11c-s12 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

Developed by: Richards, Reed, Ruzycki Updated: February 2004 U3-m10/11c-s13 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"

Developed by: Richards, Reed, Ruzycki Updated: February 2004 U3-m10/11c-s14 Stage (Depth) Measurement Devices  Non-recording staff gage  Float sensors  Ultrasonic sensors  Pressure transducers Ultrasonic depth sensor NRRI Pressure transducer Staff gages (Forestry Suppliers)

Developed by: Richards, Reed, Ruzycki Updated: February 2004 U3-m10/11c-s15 Stage-Discharge Relationship  Compute discharge at a range of stages  Plot depth vs flow and fit a curve

Developed by: Richards, Reed, Ruzycki Updated: February 2004 U3-m10/11c-s16

Developed by: Richards, Reed, Ruzycki Updated: February 2004 U3-m10/11c-s17  Importance of flow/discharge in determining loading  Slide to be completed by 3/31/04

Developed by: Richards, Reed, Ruzycki Updated: February 2004 U3-m10/11c-s18 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 