The information that StreamStats provides in reports for data-collection stations is maintained in a database that must be updated by scientists who work in our USGS state offices. These offices generally rely on partnering with local agencies to cover at least half of the cost of the needed database work. Often, the database is updated as part of the process of initially implementing StreamStats, but additional updates subsequent to implementation and updates for states that are not implemented are difficult to achieve. As a result, a lot of the data in our database is out of date. The StreamStats development team plans to reduce this problem during 2016 by beginning a process of annually updating a set of about 100 non-interpretive statistics, which can be computed automatically by a computer without human intervention. These non-interpretive statistics will include means, medians, minimums, maximums, and standard deviations of annual, monthly, and daily flow time series for streamgages, as well as harmonic means and flow-duration percentiles computed from the daily flows. However, low-flow and peak-flow frequency statistics, such as the 7-day, 10-year low flow and the 100-year (1-percent probability) peak flow, are considered interpretive, meaning that a scientist needs to use professional judgment when computing those statistics. As a result, it is not possible to automate the updating of those types of statistics.
The most recent interpretive statistics that are available for streamgages within a state generally are in reports that are cited on the StreamStats state introductory page for that state, if the state is implemented. A more comprehensive list of reports that contain regression equations and computed interpretive streamflow statistics for the streamgages used to develop the equations is at http://water.usgs.gov/osw/programs/nss/NSSpubs_Rural.html. Also, the USGS office for each state maintains a web page at http://xx.water.usgs.gov, where xx is the 2-letter postal cost for the state. The web pages normally provide links to publications that have produced by scientists in that state. A search of these publications may turn up additional reports that contain streamflow statistics.
If you need newer statistics for streamgages and can't wait for the UGGS to make them available, then you may be able to compute them yourself. You can download time series of daily flows needed to compute most flow statistics and annual series of instantaneous peak flows needed to compute flood-frequency statistics from our NWIS-Web site at http://waterdata.usgs.gov/nwis. The USGS's PeakFQ program is available for computing peak-flow frequency statistics. It can be downloaded at http://water.usgs.gov/software/PeakFQ/. This software uses procedures prescribed by the Interagency Advisory Committee on Water Data in Bulletin 17B. Users should note that a new version of PeakFQ is expected to be released with the release of Bulletin 17C during 2016. The new version of PeakFQ will incorporate the new methods for computing peak-flow statistics that will be prescribed in Bulletin 17C.