The amount of water flowing in a stream is called its discharge, which is the volume of water moving in a stream during a given time interval, usually seconds.
River discharge = cross-sectional area x velocity of the river. The cross-sectional area = width of the stream x mean depth. This means, to calculate river discharge, we need to calculate the channel depth and width which leads to the cross sectional area; and channel velocity. Firstly am going to calculate river velocity.
Average Velocity (speed):
River velocity differs in different parts of the river. Due to the friction of the roughness of the bed material, the flow of the water is slowest at the bottom and fastest at the top. Velocity is also affected by the depth of the river as the deeper it is, the more cross sectional area of the slow flow there is. So where is it suitable for me to measure the river velocity? To work out a river’s velocity, which, as we know changes with the river’s depth. Therefore the best way to find a river’s velocity is to calculate the average speed of the stream. But the question still remains, where can I measure the average velocity of the river?
To calculate the average velocity of a river, we use a float and a hydro prop. A float is a small tube with a few pebbles comes to make it float. First, we have to measure an appropriate distance in a river, where we will be able to count how long it took to cover the ten meters up, and we will assess how fast the river flows compared to the other three sites that we will visit. Then we will drop float in the river and count how long it will take to get the whole ten meters using a stopwatch. However we have to repeat this process three times: the left side of the river, middle and right side of the river. The reason for this is so that we have the average speed as the current flows swiftly on the outside of a river, where it goes.
Load particle size: To find the load particle size of a river, in the first place, we had to collect a reasonable amount of load from the river bed and measure each stone from the longest side for a fair examination.
Channel Width: The channel width will increase as you move down stream.
We will measure the channel width by using a tape measure, measuring from one side to another.
There may be too much vegetation on the river bank, preventing us from getting the exact measurements.
We will try to measure the width where there is less vegetation.
Channel depth: To measure the depth channel, we have 10 measurements across the occupied channel width and the sum divided by 10 for the calculation of the average. The reason for finding the average is because the river bed is not so straight because the sediments of the deposits.
Pebble length: The length of pebbles will increase as you move down stream.
We pick up twelve random pebbles from the river, we then throw away two and measure the longest side. Some pebbles may be too small to measure. As you pick up twelve pebbles try and pick up larger than smaller pebbles for easier measurements.
Powers Index of Roundness and Sphericity: The length of pebbles will increase as you move down stream; the roundness of the pebbles will increase as you move down stream. Picked ten random pebbles out of the river, measured the roundness of them in miller meters. Some pebbles may be too small to measure the roundness or some may have ridged or sharp edges. Pick up several large pebbles that are fairly round with no sharp ends.
Discharge- is the amount of water you have, and how much of it will pass through a certain point. I presume will decrease due to less water availability downstream.
Hydraulic Radius- will become more efficient due to less water touching the banks as well as the depth increasing as the two are linked.