Our Steve Grimmer has been filming experiments in an Emriver Em3 stream table focusing on the groundwater system.
This is his first video in the series. Scroll down to see it!
Groundwater is water that’s below Earth’s surface in soil pore space or rock fractures.
The Emriver groundwater system allows for injection and extraction of subsurface flow. A small pump supplies a spray bar with tubes at the upstream end of the table to produce groundwater flow. Extraction filters are located at the downstream end of the table. The injection and extraction can be increased, decreased, or turned off.
Even without the optional groundwater system, our stream tables display the results of groundwater processes. The stream table charges with water so that it has a water table beneath the sediment outside the stream. The effects of underground directional flow can be seen, including strata formations and floodplain terraces. Patterns left behind demonstrate how groundwater once flowed in an area.
The plastic media we use in our stream tables is particularly good at forming sapping channels, which are groundwater-driven gullies.
You can see the effects of contaminants in a stream on groundwater, and vice versa, by digging a well outside the stream and adding dye to the well. Aside from contaminants, the dye also acts as a marker to show water flows between the stream and the water table (groundwater) outside the stream. By using dye, you can also demonstrate how groundwater interacts with water in a channel, even when it isn’t contaminated. These exchanges are known as groundwater/surface water interactions.
Here are the details of the groundwater system experiment:
Initial conditions are a well-wetted media bed in the stream table with existing channels from previous experiments, set to 1.5 degrees slope.
The K500 flow controller was started at 20 ml/sec for ten minutes to establish a stable main channel.
After that time, the groundwater controller was set to 20 ml/sec to form a gaining stream and tributary to the main channel.
Off-screen to the left, a groundwater-fed lake formed spontaneously, and the results of it over-topping its dam can be seen in the sudden flood at the 50-second mark.
The sediment depositing in the main channel quickly ends the main channel meandering.
Additional Information: In the stream table, the lower stream is the main channel, which is from the K500 controller. The upper stream is from the groundwater system. The spray bar for the groundwater system is set at an angle on the Em3 box, not straight across as is “typical.” You can see the EDU for the K500 in the bottom-left of the frame and the spray bar in the upper left corner.