# Determination Now in this step we will calculate

Determination the velocity & discharge using floats

APPARATUS:

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1)    Tape
Measure

2)    Stop-Watch
cell phone having a timer

3)     Meter stick TO Measure Depth (Tape Measures
are not possible to use)

4)    Buoyant
objects such as orange

THEORY:

If a Flow Meter is not Available or Rough
Estimate is enough so we can use the float to calculate the flow. The float can
be any light object such as pine cone or an orange or partially filled plastic
water bottle.

The basic idea is to Measure the time that it
takes a floating object to travel a specified distance downstream. We measure
the flow of stream. Flow is important because define the shape, size and
direction of the stream.

Measure the distance up to 50 feet along the
bank string the rope at the both ends.

1.    Using
the total stream calculate the cross sectional area of the stream at the both
end. To find the total stream width and the average depth.

Total Width (feet)*
Average depth (feet) = area in feet.

2.    Throw
The Float From Upstream Direction. Get a stop watch to record the time it takes
to reach the downstream. If the float moves too fast so record the data 75 or
100 instead of 50 feet. Now repeat the process two more times for a total of
three measurements.

3.    Now
in this step we will calculate the velocity the distance covered by float
divided by the average amount of time it took to cover the distance.  If the distance is 50 feet and the time
covered by a float/orange 100 seconds so get the velocity is 0.5 feet/sec.

50 feet/100sec=0.5sec.

4.    Calculate
the mid-depth of stream velocity by multiply the surface velocity by 0.85.

0.5×0.85=0.43ft/sec.

5.  Now calculate the discharge in
cubic feet/second (cfs) & multiply the

Velocity (ft/sec) by the cross-sectional area (ft.) of the stream.

0.43ft/secx10.73ft=4.62cfs.

USING A STAFF GAGE

The staff gage is a long ruler placed half-permanently
in a stream or lake used to measure the water depth. Staff gages are the most  useful & common for measurement. place the
staff gauges in a lake. Place the three staff gauges because in mid portion the
lake water velocity is different as compared to the side of lake. There is some
resistance at the side of lake that’s why we place the multiple staff gauge. If
a staff gauges place on non-vertical place so knowing that the staff gauges

WHY WE
USE  STAFF GAGE

We can use a staff gauge to get the information
in an indirect way to calculate the stream flow. If we place the staff gauge
near a section of stream for which you are collecting flow data, you can
identify the relationship between stream depth & stream flow. Once you got
this relationship so we can calculate flow from the stream depth without having
to take a time to make a detailed flow measurement. A staff gauge having
numerically labeled divided in lines to take the measurement of water &
calculate easily the depth & stream flow.