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Pennsylvania StreamStats

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, the Pennsylvania Department of Transportation and the Susquehanna River Basin Commission.

Pennsylvania StreamStats incorporates regression equations for estimating numerous streamflow statistics. Equations are included for estimating flood flows associated with the 2-, 5-, 10-, 25-, 50-, 100-, 200-, and 500-year recurrence interval floods, which have the probability of exceedance in any single year of 50, 20, 10, 4, 2, 1, 0.5, and 0.2 percent, respectively. Equations 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 these reports before using StreamStats to obtain estimates of streamflow statistics for ungaged sites.

Underlying StreamStats application datasets were updated for Pennsylvania in 2020, to include the use of updated National Hydrography Dataset (NHD) flowlines and Watershed Boundary Dataset (WBD) boundaries.  GIS datasets are available in the Data Releases below.

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


  • Mean basin slope is used in the regression equation for low-flow region 1 and flood-flow region 5. For the low-flow regression equation equations, an adjustment factor is applied to the basin characteristic mean basin slope to more accurately replicate the values used to develop the regression equations. Both the raw (unadjusted, BSLOPDRAW) and adjusted basin slope values (BSLOPD) 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. For the flood-flow regression equations, an unadjusted basin slope is displayed (BSLOPDRPA20), which was derived from a slightly different source.
  • 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 

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