Streamflow recession indices computed by automation within and proximal to the Mobile Bay and Perdido Bay watersheds, south-central United States

This data release presents streamflow recession analyses and supporting statistics for 164 U.S. Geological Survey (USGS) streamgages located in or near the watersheds of Mobile and Perdido Bays in the south-central United States (see Tatum and others, 2024). Streamgages were selected based on a minimum of two complete decades of daily streamflow data since January 1, 1950, with the additional requirement that data coverage includes the entire 2010s decade. Daily streamflow data were retrieved on March 8, 2024 (U.S. Geological Survey, 2024). The primary output of this release, gfactor.txt, is a pipe-delimited text file containing 22 attributes and over 1,000 unique records summarizing decadal streamflow statistics for each site. Key identifying attributes include the USGS site identification number (site_no), streamgage name (station_nm), geographic coordinates (dec_lat_va, dec_long_va), contributing drainage area (CDA), and projected coordinates (xkm, ykm). Key statistical attributes consist of decadal counts of daily streamflow conditions (decreasing_count, increasing_count, nochange_count, total_count), as well as summary statistics that characterize the declining days distribution, including the 50th percentile (median), L-moments (L1, L2, T3, T4, T5), and streamflow recession indices associated with the 90th percentile (gfactor, gfactor_emp). Additional attributes capture adjusted statistics produced through a detrending procedure designed to assess and remove potential decadal biases in the declining day distribution. Core statistical computations were carried out using custom functions developed in the R environment for statistical computing (R Core Team, 2024).