Stream discharge is a significant factor that characterizes many aspects of the stream function. For example, by measuring the stream discharge we can determine the amount of water available to meet instream and extractive water uses. Stream discharge can also be used to find out the habitat diversity and the rates of nutrient export of a stream. One of the most common approaches to measuring discharge is the velocity-area method and it involves measuring water depth and velocity at a point across a stream section with a current meter. Another method of stream discharge measurement consists of injecting a chemical tracer and determining its dilution after complete mixing into the flow. There are two variations in this dilution gauging method depending on whether the tracer is injected into a stream at a constant rate or a near-instantaneous "slug ". Nevertheless, for both cases the tracer is injected at some point along the stream, and the tracer concentration in stream water is measured at a downstream point, where the tracer has become uniformly mixed with the stream water. .
Method.
This lab is taken place in the Khorana Park at Westbrook village in UBC. The streams that were being measured are constructed by humans and it has a medium turbulence rate. The average depth of the stream is 5cm and is measured by every 10cm of the width. There is no vegetation or obstacles present within the stream to affect the velocity, depth and discharge. .
The first method we used to estimate the discharge of the stream is the velocity-area method. We will calculate the cross-sectional area of the stream. The width is measured to be 92 cm and the average depth is 5cm. The area is then calculated by multiplying the average depth with width. We took a cap from a bottle as a floating device and we used a stopwatch to measure the time it takes for the cap to travel 20m in the stream. This process was repeated for three times to estimate the average discharge.