Describe spreadsheet.

Author: awickert

README.md

@@ -8,4 +8,12 @@ Example [OTTAR](https://github.com/MNiMORPH/OTTAR) model outputs from:
 
 These folders include the best-fitting model results, simulated with the help of [DAKOTA](https://dakota.sandia.gov/), alongside configuration files to reproduce these best-fitting results and test parameter sensitivity.
 
+The spreadsheet contains source data alongside computed mean and standard-deviation channel widths for the Minnesota River, the Cannon River, and Diamond Fork. Mean and standard deviation widths for the Green River are from Walker et al. (2020).
+
+## Licenses
+
 The supplied GNU GPL v3 license applies to the software and configuration files. Base data files from the US Geological Survey are public domain. Channel-width observations and data not in the public domain are licensed under the Creative Commons license also supplied here.
+
+## References
+
+Walker, A. E., Moore, J. N., Grams, P. E., Dean, D. J., & Schmidt, J. C. (2020). Channel narrowing by inset floodplain formation of the lower Green River in the Canyonlands region, Utah. GSA Bulletin, 132(11-12), 2333-2352.