Module 10/11Stream 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 sensorNRRI

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 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/