Module 1011 Stream Surveys February 2004 Part 3

Module 10/11 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. · explain the stage-discharge relationship. Developed by: Richards, Reed, Ruzycki Updated: February 2004 U 3 -m 10/11 c-s 2

Stream assessments · Water quality · Habitat · Hydrologic · Biological · Watershed Developed by: Richards, Reed, Ruzycki Updated: February 2004 U 3 -m 10/11 c-s 3

Hydrologic assessments Developed by: Richards, Reed, Ruzycki Updated: February 2004 U 3 -m 10/11 c-s 4

Stream Hydrology · Velocity · Discharge (flow) · Stage-discharge relationship Developed by: Richards, Reed, Ruzycki Updated: February 2004 U 3 -m 10/11 c-s 5

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 U 3 -m 10/11 c-s 6

Velocity – Current Meters · · Propeller type meters Electromagnetic meters using waves to measure velocity · (e. g. March-Mc. Birney). Developed by: Richards, Reed, Ruzycki Updated: February 2004 U 3 -m 10/11 c-s 7

Velocity – in stream sensors · Useful for long-term velocity measurement in one place · Not for use in discharge determination Son. Tek (YSI) Bubbler flow sensor (Campbell Scientific) Developed by: Richards, Reed, Ruzycki Updated: February 2004 U 3 -m 10/11 c-s 8

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 U 3 -m 10/11 c-s 9

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 U 3 -m 10/11 c-s 10

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 U 3 -m 10/11 c-s 11

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 U 3 -m 10/11 c-s 12

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 U 3 -m 10/11 c-s 13

Stage (Depth) Measurement Devices · Non-recording staff gage · Float sensors · Ultrasonic sensors · Pressure transducers Pressure transducer Ultrasonic depth sensor NRRI Developed by: Richards, Reed, Ruzycki Staff gages (Forestry Suppliers) Updated: February 2004 U 3 -m 10/11 c-s 14

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 U 3 -m 10/11 c-s 15

Developed by: Richards, Reed, Ruzycki Updated: February 2004 U 3 -m 10/11 c-s 16

· Importance of flow/discharge in determining loading · Slide to be completed by 3/31/04 Developed by: Richards, Reed, Ruzycki Updated: February 2004 U 3 -m 10/11 c-s 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/Field. Manual/ · Rapid bioassessment protocols for wadeable streams · http: //www. epa. gov/owow/monitoring/rbp/ Developed by: Richards, Reed, Ruzycki Updated: February 2004 U 3 -m 10/11 c-s 18