Select a section of stream that is relatively straight, free of large objects such as logs or large boulders, with a noticeable current, and with a depth as uniform as possible. Stretch the tape measure provided by the program across the stream. The "0" point should be anchored at the wetted edge of the stream. The end of the tape measure should be anchored at the opposite end so that it is taut and even with the other wetted edge.

In the table below, record depth measurements at along the tape measure you have stretched across the stream. For streams less than 20 feet wide, measure the depth every foot. For streams greater than 20 feet wide, measure the depth every two feet. The depth must be measured in tenths of a foot (i.e., 1.7 feet equals of one foot and seven tenths). DO NOT MEASURE THE DEPTH IN INCHES.

For a stream less than ten feet in width, select three points in the stream approximately equal distances apart for velocity measurements. For streams greater than ten feet in width, no fewer than four velocity measurements should be taken at approximately equal distances across the stream. For example, if the stream were eight feet wide, then velocity measurements would be taken at approximately two foot intervals across the stream in order to derive four measurements. If the stream were sixteen feet across, then velocity measurements would be taken at approximately three foot intervals across the stream in order to derive four measurements . This method of measuring the stream velocity will ensure that velocity measurements are recorded for the slow and fast portions of the stream.

Once you have determined the number of velocity float trials you need to complete, measure the water's surface velocity in the following manner. Select two points located an equal distance upstream and downstream from the tape measure you have stretched across the stream. Determine the distance between these two points and record this value (in feet) in the Distance floated in Velocity Float Trials box below. Count the number of seconds it takes for a buoyant object (such as an orange or an apple) to float this distance. Record this time (in seconds) in the table below for each float trial you complete.

Average Depth = Sum of Depths / Number of Intervals
To calculate the average depth of the stream, divide the sum of depth measurements (in the Stream Depth table) by the number of intervals at which the measurements were taken.

Cross Sectional Area = Average Depth x Stream Width
The cross sectional area is the average depth multiplied by the stream width.

Average Float Time = Sum of Float Times / Number of Trials
The average float time is equal to the sum of float times (in seconds) divided by the number of float trials (in the Velocity Float Trials table).

Average Surface Velocity = Distance Floated / Average Float Time
The average surface velocity is calculated by dividing the distance floated by the average float time.

Corrected Average Stream Velocity = Correction Value x Average Surface Velocity
The correction value depends on the bottom of the stream you are measuring. If the stream bottom is rough, with loose rocks or coarse gravel, then the correction value is 0.8. If the stream bottom is smooth, mud, sand, or hard pan rock, then the correction value is 0.9. This corrects for the friction (drag) on the stream bottom.

Stream Discharge = Cross Sectional Area x Corrected Average Stream Velocity
You can calculate the stream discharge by multiplying the cross sectional area by the corrected average stream velocity.