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Gauging Activities

Things to bring:

Lab equipment: (all equipment except your lab notebook) will be supplied by the TA)

Gauging Parameters to be Measured

Please refer to the textbook (Chapter 3, Sanders, 1998) for a detailed description of the measurement of each parameter listed below. In the field, we will break up into 3-4 groups, each group will be responsible for measuring the parameters listed below at a station assigned by the TA or professor. We will then move to the picnic area in the park to discuss data analysis, and compare results. At this time or later you will write up your laboratory procedures and results (due at the beginning of the next lab). In your discussion you will describe your group's results, compare them to those of the other groups, and explain any observed variation.

Parameters to be measured:

* Stream Cross-Section
measured directly using simple surveying techniques (Fig. 3.3). Used to determine the cross-sectional area of the stream, also hydraulic radius and wetted perimeter (see text p. 53-55).
* Stream Velocity
determined by float method (Fig. 3.7) and direct measurement when possible (impeller velocity meter, Fig. 3.10 and Section 3.1.3). Used to compute discharge (see also text p. 73-74).
Parameters to be calculated:
* Discharge
given cross-section and stream velocity measurements described above

Gauging Tasks

  1. At 3 or 4 places along the stream, we will install a tag line (either a distance-marked string or chalk-mark on the concrete) approximately perpendicular to the stream. In your notes, identify these stations using roman numerals, starting with I at the upstream-most line.
  2. Each group will use yardsticks or rulers provided by the TA to measure the vertical distance from the tagline to the water surface, and to the stream bed at suitable intervals along the line. These intervals must be spaced closely enough to allow accurate determination of the stream cross-section (see Figs. 3.2-3.3).
  3. A second line will be installed an appropriate distance downstream from the tag line, to allow velocity determination by the float method
  4. Each group will measure the surface velocity at several points along the tag line, and determine an average surface velocity (Figs. 3.7-3.8).
  5. If there is sufficient water depth, each group will also utilize the impeller flowmeter to determine the variation of velocity with depth, and to compare to their float-method velocity values. The flowmeter can be used to measure an average velocity across small stream cross-sections
  6. If low water conditions are present, use the blue tub to measure the discharge from the stream. Time how many seconds it takes to fill the tub to the indentation mid-way up the side (which is the 15 liter volume mark). Divide the volume by the time to get the discharge.
  7. Calculate your discharge values and report them to the other groups (preferably via WebCT) within one week after the lab.

Suggested form for recording stream cross section data:

Stream Cross Section Measurements
Name: Date:
Team Members:
Tag line endpoints (lat, long, elev):
Point Number Horizontal Position Distance to Water Surface Distance to Stream Bottom Notes

Suggested form for recording stream velocity data, float method (after p. 63, Sanders, 1998)):

Stream Velocity Measurements (float method)
Name: Date:
Team Members:
Stream Section Number Section Width Downstream Distance Trial Number Time Surface Velocity Average Surface Velocity in Section Notes

See page 67, Sanders (1998) for a suggested form for recording stream velocity data, velocity meter method.

Writeup Suggestions

In your lab writeup, please pay attention to the grading criteria (section 2.2). In your discussion, you may want to consider the following factors that can affect stream discharge (after p. 50 Sanders, 1998):
  1. General topographic setting
  2. Site-specific topography and relief (a sketch or profile may be helpful.
  3. Character of the floodplain and floodplain development.
  4. Description of the stream banks and bed.
  5. Sediment and rock exposed in cuts and in the stream bed.
  6. Soils on the bank and washover deposits.
  7. Vegetation: plant species, density and condition
  8. Evidence of animal activity in the stream
  9. Field observation of moisture content of the floodplain soils.
  10. Depositional features
  11. Erosional features
  12. Human development
  13. Evidence of flooding events
  14. Bank stability


next up previous contents
Next: Water Quality Measurements Up: Streamflow/Stream Gauging Previous: Gauging Background
GEOS 3110 Professor's Notes, Summer 2007
Dr. T. Brikowski, U. Texas-Dallas. All rights reserved.