Correction Notice for Development of
the Beta Streamflow Duration
Assessment Method for the Arid West

Correction for the analysis described in Mazor, R.D.; Topping, B.J.; Nadeau, T.-L.; Fritz, K.M.; Kelso, J.E.;
Harrington, R.A.; Beck, W.S.; McCune, K.S.; Allen, A.O.; Leidy, R.; et al. Implementing an Operational
Framework to Develop a Streamflow Duration Assessment Method: A Case Study from the Arid West
United States. Water 2021, 13, 3310. https://doi.org/10.3390/wl3223310.

Data analysis used to develop User Manual for a Beta Streamflow Duration Assessment Method for the
Arid West of the United States EPA-800-K-21001

November 2023

The Beta SDAM for the Arid West published in March 2021 and the journal article describing the data
analysis published in November 2021 contained errors in the calculation of at least intermittent and
needs more information classifications. These errors have now been corrected in the web application
through updates to the User Manual, see version 1.1 dated November 2023. The errors caused sites to
be identified as at least intermittent that should have been identified as perennial or intermittent
instead. The errors also caused sites to be identified as needs more information that should have been
identified as intermittent, ephemeral, or less than perennial instead. In the dataset used to develop the
beta SDAM for the Arid West, 90 sites were assessed and the classification results for 31 of them were
affected by the errors (28 should have been perennialintermittent, or ephemeral; 3 should have been
less than perennial). Correction of the errors also eliminated needs more information as a classification
outcome. No classifications of perennial, intermittent, or ephemeral by the version 1.0 beta method
were affected by the errors.

The data analysis steps described in the November 2021 journal article accurately describe the process
followed to develop the beta SDAMs for the Arid West; however, the results for at least intermittent and
needs more information are over-represented, and the occurrences of less than perennial classification
is wholly missing. Applying the corrected calculation of classifications, the beta method for the Arid
West correctly classified 71% of site visits among three classes (perennial vs. intermittent vs. ephemeral),
while 88% of site visits were classified correctly between two classes (ephemeral \/s. at least
intermittent).

-------