Physical monitoring #
Category: Watershed 101
Physical monitoring
Physical monitoring involves recording all of the physical parameters of the stream. This means recording the characteristics of the stream itself and the area surrounding it.
Common physical attributes to measure are: surrounding cover, type of stream bottom, stream width, depth, velocity, and discharge. the cover surrounding a stream can greatly influence its characteristics. It is important to note if any of the stream is covered by trees or particularly in the sunlight. This can affect the temperature of the water and the organisms found in it. The type of stream bottom can also determine what kinds of macro invertebrates that are likely to be present.
Physical monitoring can be divided into three very important sections of testing:
Flow Temperature #
Visual Observations #
These parameters, used in conjunction with other monitoring techniques, are extremely useful in diagnosing and caring for the stream or water way.
Weirs #
A weir is an overflow structure that is built in-stream, perpendicular to the direction of flow, and measures the water’s flow rate. A weir will impound water behind it, acting like a small dam, so site locations must be evaluated before construction. Many weirs are situated on smaller streams in areas where current meter measurements are not applicable. This type of structure is frequently utilized to establish stream flow over long periods of time. Flow measured over an extended period of time helps to establish a rating curve, which will allow flow to be predicted at that location. A weir can be constructed of any type of sturdy material, such as wood, metal or concrete.
The type and size of weir chosen for your site will depend on the flow characteristics of the stream. There are two commonly used types of weirs, V-notch and rectangular. A notch weir is designed to measure small flows and a rectangular weir to measure larger flows.
Flow Monitoring #
Conducting the rest of the measurements is much easier with at least 2 people. It is very easy to measure stream width by stretching a tape measure from bank to bank across a relatively level section of stream. Depth can be easily measured by using a meter stick to measure the depth at various points along a cross-section of the stream. A cross-section of the stream can be drawn using the width and depth of the stream. This could be a useful tool to map water levels at various points in time to determine if the stream is at normal level, running dry, or higher than usual. It is a wise idea to avoid entering streams that are higher than normal as currents may be strong.
Stream velocity and discharge are relatively easy to determine. To monitor stream velocity (or flow rate), use either a flow-rate meter (an expensive piece of equipment) or measure it yourself. Before measuring the velocity, mark out a length of approximately 10 meters on a relatively straight portion of the stream. Simply drop a bobber or other easily visible, floating object into the stream to the 0 meter mark. Start timing on a stopwatch and stop when the object reaches the 10 meter mark. To calculate to velocity divide the distance traveled (10 meters) by the time in seconds.
Finding the discharge of a stream is simply a calculation.
Discharge (m3/s) = Stream width (m) x Average Depth (m) x Velocity (m/s) x Constant
The constant is not necessary, however try to include it whenever possible. Multiply by 0.8 for gravel or rocky bottom streams or 0.9 for sandy or muddy bottom streams.
See St. Vincent College Environmental Education Center module on Flow. http://facweb.stvincent.edu/EEC/pdf/flow.pdf
The USGS has set up many gaging stations throughout the state to record the height of the water level of many creeks and rivers. Your waterway may already be in the monitoring group, click here to find out. http://wwwpah2o.er.usgs.gov/pa_hydro.htm l
Other important AMD tests
Temperature Acidity Dissolved Oxygen (DO) pH Aluminum Flow AlkalinityTotal Dissolved Solids (Conductivity) IronManganese
Temperature #
Temperature is a very important characteristic to consider when monitoring a stream or waterway. The temperature not only determines what organisms live in the waters, but also can give clues to pollutions sources. Fish are divided into cold water and warm water families. Often Brook Trout and other cool water fish inhabit the headwaters and upper reaches of streams. These areas are more likely to be shady and cooler. Warm water fishes are found further downstream, near the mouth of a waterway. These fish prefer more open water with less shade and increased temperatures.
The temperature of water contaminated by AMD may be very cold. AMD travels from deep underground mines into the surface water of the stream. This keeps the AMD discharge at the same temperature as the underground reservoir it is coming from. Most discharges range between 13 and 15 degrees Celsius, much colder than average surface water.
Don’t confirm that there is an AMD discharge by temperature alone. It is best to monitor other factors such as pH and iron as well before confirming the presence of AMD.
Most any thermometer can be used to measure the temperature of the stream. Try to choose one with easy to read scales, however to make the readings easy and accurate. Often chemical monitoring meters will read the temperature of the water as well as the factor they are supposed to measure. If you possess such a monitor, the temperature can be recorded using it rather than a thermometer.
Other important AMD tests
Temperature Acidity Dissolved Oxygen (DO) pH Aluminum Flow AlkalinityTotal Dissolved Solids (Conductivity) IronManganese
Visual observations
The physical characteristics of a stream can give clues to the health of the stream. Healthy streams have lush riparian buffers, clear water and plenty of wildlife.
A stream walk is often a good way to become acquainted with your watershed. Choose a section of stream and walk alongside of it for a distance. This will allow you to become familiar with the variety of vegetation and wildlife that can be found in your watershed. Be sure to make notes of what you see and mark anything of interest.
AMD pollution is often visible in the form of “yellow boys”. This is a yellowish-orange film that coats the rocks and twigs on the bottoms and sides of the waterway. In some AMD treatment options this precipitate, iron oxide, can be harvested for use. Iron oxide is one of the most common compounds used to make red dyes.
High acid levels, usually resulting from AMD, may also cause aluminum or other heavy metals to dissolve in the water. High aluminum levels eventually lead to the metal precipitating out of the water onto the bottom of the stream creating a whitish film.
Sources/Links (as provided in the source text):
- http://facweb.stvincent.edu/EEC/pdf/flow.pdf
- http://wwwpah2o.er.usgs.gov/pa_hydro.htm
