Ratings and estimated provisional streamflow for streamgages in Virginia, water years 1991 through 2013

The U.S. Geological Survey, in cooperation with the Virginia Department of Environmental Quality, has quantified several measures of rating stability and the frequency and magnitude of changes to ratings through time for 174 real-time continuous streamgages active in Virginia as of September 30, 2013. Alternative flow (AltFlow) tables were developed as a method of estimating provisional flow data. They were constructed for periods with complete records of shifts and ratings between October 1, 1990 and September 30, 2013. Alternate flows consist of Qsame, the flow value from the shifted rating table used to compute the daily flow value at the time of the most recent flow measurement that corresponds to the gage height of each day's daily flow value, and Qprev, the flow value from the shifted rating table in effect at the time of the previous flow measurement that corresponds to the gage height of each day's daily flow value. These AltFlow tables were limited in several important ways that are discussed in the report; most important among them are that they were not developed from the ratings that were in place at the time provisional data were initially published to the web. This data release is comprised of the AltFlow tables and the expanded, shifted ratings used to develop them. Data are grouped by major river basin. Expanded shifted ratings and AltFlows are provided in five Microsoft Excel files. These files include the formulas used to compute the AltFlow tables. These files may be used to extend the AltFlow record for Virginia past the end of the study period, or develop an AltFlow record for another state, using procedures described in Appendix 2 of the companion report (Messinger and Burgholzer, 2018). The AltFlows are also provided in comma-separated variable (csv) files, one file for each major river basin, without formulas and without the fields used only for processing and computation.