How to Construct a Classroom Stream Table:
A classroom stream table should be able to accommodate a group of 5-6 students at a time. You will need a watertight container, such as an under-the-bed storage container, that is at least three feet long. The longer, the better. Sterilite makes one that is 44 inches long and costs under $20.00. In my class, I used a sandbox that I found at Toys R Us.
Once you have located a container, the next step is to fill it with a substrate. The least expensive option is to use sand sourced locally. A mix of silica, clay, and gravel will work and you will need about 80 pounds of it. Another option is to use ground walnut shells. Ground walnut shells are often used in the metal polishing industry and can be easily be sourced online. A third, and more expensive, option is to use plastic granules sold by http://www.emriver.com/. Their plastic modeling compound is color coded based on grain size and is an ideal and clean material. Unfortunately, the cost for this material will range between $4,000.00 to $6,000.00, compared to about $50 for purchased sand.
You will need to construct a drain plug on one of the short sides of the container, approximately one inch above the bottom. A small “L-shaped” pipe (about 1 inch diameter) will suffice. I recommend using a metal washer on each side where it connects to the container. Use an adhesive caulk or epoxy to insure a watertight connection. The bend in the pipe should be facing down. Use plastic or vinyl tubing to make a drain hose that attaches to the drain spout. You will want at least three feet of tubing. A 5 or 10-gallon bucket should be used to collect the water. I recommend gluing a screen to the inlet of the drain spout to help prevent clogging of the tubing.
Now that you have a stream table bed and drain created, the next decision is to determine if you want to use a small aquarium pump to recirculate the water, or if you want to simply swap buckets and recirculate the water manually. I recommend using an adjustable aquarium pump rated at a maximum of 120 gallons per hour. Anything higher is too fast of a water flow. Aquarium pumps are submersible, so simply attach about 5 feet of tubing to the outlet of the pump and place the pump in your drainage bucket. Attach the other end of the tubing to the opposite end of the stream table using a small clamp.
Once the water pump is connected, at the substrate you selected. Fill about 2/3 of the container with the substrate at the top of the stream table, where your water flow begins. Be sure that your drainage bucket has ample water to provide a continuous flow of water. You may need to add water to prevent the pump running dry. The pump needs to remain submerged or it can quickly overheat and become damaged.
Add plastic foliage, small rocks, and other materials to give your model a more realistic representation of natural conditions. Green Christmas tree garland is a good substitute for grass. Use blocks of wood to adjust the slope of the table.
How to Construct a Personal Stream Table:
In addition to a classroom stream table, students can also create a small-scale model on their own. Each student (or pair) will need a small tray such as the ones used in the cafeteria. Use a few scoops of cornmeal as a substrate, and place it in a mound on one end of the tray. The tray does not need to be sloped. Students will need a few blocks or books to make support towers that hold a ruler above and across the mound of cornmeal. Use a pin to make a small hole in the bottom of a paper cup, place the cup on the ruler so that the hole is above the cornmeal, and fill the cup about 2/3 full of water. Water will slowly drip through the hole and carve landforms into the cornmeal. Be careful not to use too much water, or you will flood the tray. You can vary the size of the hole to adjust the water flow.