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WQ – Streams – Clarity – Trends

Data Categories:
Data Source:MN Pollution Control Agency, Natural Resources Research Institute
Update Fequency:Annually
Date Acquired:12/15/2019
Data Available:Yes
Metadata Available:No

This data layer indicates trends in stream clarity based on 100 cm long transparency tube measurements. It was developed by the Natural Resources Research Institute using data from the Minnesota Pollution Control Agency. A transparency tube measurement is analogous to a Secchi depth measurement for lakes. A regression model (specifically a Tobit model) was used to detect changes in water clarity over time by comparing months across years. This test also accounts for the limit of the Secchi tube to detect water clarity of more than 100 centimeters. Stream water clarity must change at least 2 cm per decade to be considered a detectable change, or trend. Decreases in stream transparency can be due to increases in suspended sediment or particles. Excessive sedimentation in streams and rivers is considered to be the major cause of surface water pollution in the U.S.

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