Streamflow was collected at various streamgages in western Pennsylvania in support of the scientific investigations report "Estimation of Base Flow on Ungaged, Periodically Measured Streams in Small Watersheds in Western Pennsylvania". Data observed at the streamgages for the period of August 1, 2014 through March 31, 2017 are considered. This dataset includes 1) all data used to develop prediction intervals for the titled estimation site based upon the titled index streamgage for the period of May 1, 2015 to March 31, 2017 and 2) evaluation of data observed before May 1, 2015. For prediction interval development, a Move.1 regression was developed between the titled estimation site and titled index streamgage. From this regression model, Pearson's correlation coefficient (r) is reported, and the Nash-Sutcliffe efficiency value is computed. The prediction interval development is included for the 95% prediction interval for both the nonparametric and parametric methods. For the parametric method, any prediction interval can be developed by changing Student's t critical value. Any data that were observed before May 1, 2015 were evaluated to see if they fell within the 95% nonparametric prediction interval. The data chosen for the regression development and evaluation is streamflow that is not influenced by runoff. Streamflow that occurred the day of precipitation and two days after is considered influenced by runoff and not included in the dataset. Not all streamgages have the same period of record; dates where data were observed both at the titled index streamgage and estimation site are described below in the "Time Period of Data" section.