Call for Water Transparency Data

The South Dakota Discovery Center is issuing a call for water transparency data from lakes, streams, rivers, ponds in South Dakota using a turbidity (or transparency) tube, often referred to as a t-tube since both transparency and turbidity start with the letter t. 

The t-tube is a simple instrument. It is a tall, transparent tube of at least 120 centimeters that is marked off in centimeters on the side. On the bottom is a quadrant pattern of alternating black and white sections. You can measure the clarity of the water by measuring the depth of the water in the tube at the point where the pattern on the bottom transitions from visible to invisible as seen from the top. If the water is cloudy, the water in the tube won’t be very high; if the water is clear you may be able to fill the water to or near to the top, as it will be visible through a full tube of water.

Water can become turbid or cloudy when rain or snow running off land into the water erodes the surface and carries the eroded material into the lake, river, stream or pond. Not all surfaces are equally erodible. There are parts of our state like the Badlands that are highly erodible and the water clarity is very low (meaning you can’t see through it easily). There are other parts, like the Black Hills, that are very resistant to erosion and therefore very see-through.

For example, a recent t- tube reading taken from the South Fork of Sage Creek in Badlands National Park* had a reading of 1 centimeter. A reading from Spearfish Creek topped out the tube which meant you could fill it to the top of the tube and still the see pattern on the bottom.

Why are we interested in t-tube data? We are building a resource to help educators address the Fourth Grade Earth Science Standard 4-ESS2-1 Make observations and/or measurements to provide evidence of the effects of weathering or the rate of erosion by water, ice, wind, or vegetation.

Students will be able to study the phenomena of water clarity in their own location and compare their data with other locations from around the state, and even the country, or world.

IPhenomena is a new approach to teaching science. Phenomena is more than a question (though it often includes a question). Rather, phenomena requires using science and engineering practices to develop understanding and an explain. See the Next Generation Science Standards Resources about Phenomena for more information about teaching with phenomena.

If you do not have a t-tube, you can apply for a mini-grant. To expedite the budgeting, please use the information from Forestry Suppliers.

To enter your t-tube data, you will need to set up your hydrology monitoring site (either on your laptop or in the data entry app).

If you have any questions, please let me know!

*You need a permit to collect water quality samples in a national park.


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Thank you for such great activity because I teach 4th grade science and we begin with Earth science 4- ESS2-1 is how I will begin my unit. I will keep you posted when we start this activity sometime in September.