StreamStats in Pennsylvania

Pennsylvania StreamStats incorporates regression equations for estimating numerous streamflow statistics. Equations are included for estimating the 2-, 5-, 10-, 50-, 100-, and 500-year recurrence interval floods, which have the probability of exceedance in any single year of 50, 20, 10, 2, 1, and 0.2 percent, respectively. Equations also are included for estimating the 7-day, 10-year; 7-day, 2-year; 30-day, 10-year; 30-day, 2-year; and the 90-day, 10-year low flows, the 10-year, 25-year, and 50-year base flows, and the harmonic mean flow, and the mean annual flow. Equations also are provided for estimating bankfull discharge and channel geometry. Water use data is also available in Pennsylvania and can be retrieved after a basin delineation is completed by clicking the "Check For Water Use" button. The reports below document the regression equations available in StreamStats for Pennsylvania, the methods used to develop the equations and to measure the basin characteristics used in the equations, references to GIS data layers used in the analysis, and the errors associated with the estimates obtained from the equations. Users should familiarize themselves with this report before using StreamStats to obtain estimates of streamflow statistics for ungaged sites.

Click on this link to obtain general information on the Pennsylvania application, as well as specific sources and computation methods for basin characteristics. 

In addition to solving the above regression equations, Pennsylvania StreamStats can be used to delineate drainage areas and to provide the basin characteristics that are needed as input for the Baseline Streamflow Estimator (BASE) program, which can estimate daily mean streamflows for 1960-2008 for user-selected sites on ungaged streams. The estimates provided by BASE assume that flows at the selected site are minimally altered by human activities. Additional information on the BASE program, including instructions for downloading, installing, and operating the program are at the following web page:


  • An adjustment factor is applied to the basin characteristic mean basin slope to more accurately replicate the values used to develop the regression equations. Mean basin slope is used in the regression equation for low-flow region 1. Both the raw (unadjusted) and adjusted basin slope values can be displayed using the BasinChars tool, however, only the adjusted value is displayed on the FlowStats form if the ungaged site of interest is within low-flow region 1.
  • StreamStats for Pennsylvania was developed in cooperation with the Pennsylvania Department of Environmental Protection, the Federal Emergency Management Agency, the Pennsylvania State Association of Township Supervisors, and the Susquehanna River Basin Commission.
  • The water use data is compiled from statewide self-monitoring water use reports submitted electronically to the Pennsylvania Department of Environment Protection (PADEP). To obtain site-specific water use data, access PADEP’s Water Use Report Viewer or PADEP’s eDMR Report Viewer for water discharge (return) data.

Link to the Department of Environmental Protection for Pennsylvania
Link to Federal Emergency Management AgencyLink to Pennsylvania State Association of Township SupervisorsLink to Susquehanna River Basin Commission