College of Engineering

Civil Engineering Department

 

 

 

 

LABORATORY REPORT

 

 

 

The experiment number:

The experiment title:

 

Date of experiment:

Due date of the report:

 

Student Name:                                        ID: :

 

 

 

 

(Fall Session- 2020)

Dr.

1. Table of Contents

1. Table of Contents
2. Objectives
3. Theory
4. Experiment Procedure
5. Calculations
6. Results Evaluation and Discussion
7. References

 

2.  Objectives

The objective of the experiment is:

1. To measure the volumetric flow rate [Q], mean velocity [v] of a channel, and cross-sectional area of small local streams. To compare the two methods of measuring discharge that is, the current meter method and the float method

Introduction

Streamflow measurement is very important as it helps predict possible flood hazards, identify possible water scarcity in the area, and determine water budgets. At a given point in the stream, the amount of water passing the designated point is a function of the flow velocity and cross-sectional area of the channel.

Q= A*V

Q is the stream discharge in m³/s, and V is the flow velocity in m/s. The equation above is known as the continuity equation. Different methods exist that are being used to measure stream discharge. This includes the current meter method and the float method.

 

3. Theory 

 

1.  Float method. It is one of the easiest, inexpensive methods, which is also very simple. The method helps to obtain the mean velocity by using a correction factor. It involves the measurement of the time taken for a given object to float a specified length downstream.

Surface velocity v_surface = distance travelled / time of travel [L/T].

To obtain the mean velocity _mean, make use of roughness coefficient k, ranging from 0.8 to 0.9.

V_mean =k* v_surface

2. Current meter method. In this method, the stream section is divided into subsections perpendicular to the streamflow, and for each subsection, depth and velocity are measured, respectively. For accuracy, the stream should be divided into subsections such that the discharge in any subsection is not more than 5- 10%  of the total discharge. For this experiment, the mean velocity is 0.4d from the bottom of the stream or 0.6d from the water surface.

 

 

Figure 1:  Discharge computation by the current ammeter method, the spacing of the vertical.

 

4. Experiment Procedure

1. Float method [ _mean= k*v_surface ] where k varies from 0.8 to 0.9 ]

Step1. Choose a location that is straight and with minimal turbulence.

Step2. Locate and mark the start point and the endpoint.

Step3. Where possible, make sure that the travel time between the two-point does not exceed 20 seconds.

Step4. Lower your object into the upstream of the stream on your upstream mark.

Step5.  Start your stopwatch once the object crosses the marker on the upstream and stop it when it crosses the marker on the downstream.

Step6. Repeat the procedure to obtain atleast three values of the time and calculate the average.

Step7. Determine the cross-sectional areas at the two points: the start and the end, and average them.

Step8. Multiply the average depths with the water widths obtained earlier. From the data obtained, estimate the discharge from the corrected velocity and the average area.

Q= V*A

2. Current meter method.

Step1. Choose a location that is straight and with minimal turbulence.

Step2. Locate and mark the start point and the endpoint.

Step3. Using a cable, boat, or a bridge, measure the depth of the stream at the specified intervals across the stream.

Step4. Measure the stream velocity using the current ammeter and determine the discharge.

 

 

 

 

5. Calculations

 

1. Obtain the stream cross-section data

interval	Water height	Interval area
1
2
3
total

 

2. By float method, measure the velocity for 1m

Area velocity  = 1/ time

3. Compute discharge Q

Where Q = A*V

Channel	Discharge [m3/s]
1
2
3
Total

 

 

 

 

6. Results Evaluation and Discussion 

 

The flow rates available in streams is one of the major consideration in water resource management. To realize the maximum economic value of our lands, the effective distribution of water resources is necessary. This can be made possible only under a proper understanding  of the stream flow and the hydrological processes affecting stream flows. Through the use of sustainable water resources, development is facilitated.

 

 

7. References

 

1.Bartram, J. (2020). Retrieved 12 November 2020, from https://www.who.int/water_sanitation_health/resourcesquality/wqmchap12.pdf