Iowa StreamStats now incorporates regression equations that can be used State-wide to obtain estimates of the seasonal (October 1 through December 31, and April 1 to June 30) 1- and 7-, and 30-day mean low flows for a recurrence interval of 10 years. These equations are not yet available in version 4. This announcement will be updated when that happens. The new equations are from the report:

• Eash, D.A., Barnes, K.K., and O’Shea, P.S., 2016, Methods for estimating selected spring and fall low-flow frequency statistics for ungaged stream sites in Iowa based on data through June 2014: U.S. Geological Survey Scientific Investigations Report 2016–5111, 32 p.

In addition to the above equations Iowa StreamStats versions 3 and beta version 4 are able to provide estimates of (1) the annual 1-, 7-, and 30-day mean low flows for a recurrence interval of 10 years, the annual 30-day mean low flow for a recurrence interval of 5 years, and the harmonic mean, (2) flow duration statistics (0.01-, 0.05-, 0.10-, 0.15-, 0.20-, 0.30-, 0.40-, 0.50-, 0.60-, 0.70-, 0.80-, 0.85-, 0.90-, 0.95-, and 0.99-exceedance probabilities), and (3) peak-flow statistics (50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probabilities, which are equivalent to annual flood-frequency recurrence intervals of 2, 5, 10, 25, 50, 100, 200, and 500 years, respectively). In addition, Iowa StreamStats can be used to estimate the probability of zero flow for the above-mentioned low-flow statistics for streams in the Southern Region of the State.