Determining a Water Budget for a Suburban Headwater Stream: McCarthy Run, Indiana, PA

McCarthy Run is a sub- watershed of Stoney Run. It is in White Township, to the west of Indiana Borough in Indiana, Pennsylvania. The watershed area covers 4.4 square miles with many houses, shopping centers, restaurants, and grassy recreation areas. Intense storms result in localized flooding. Current flood remediation efforts have focused on increasing retention volumes. Quantifying the volume of water that is supplied to the stream by direct surface runoff vs. stormwater infrastructure (piped) delivery for each of the small first order streams will allow for a better understanding of the mainstem of McCarthy Run. This can help the community prepare for the expected change in storm intensity predicted in the future (USGCRP, 2018).

To characterize a local water budget, we have instrumented the watershed with a variety of data collection devices. Data collection has included rain gauges, barologgers and in situ Solinst data loggers that measure water temperature, conductivity, and water pressure(depth). Rating curves have been created based on both topographic field surveys and flow discharge measurements. The rating curves allow for the quantification of discharge, even at high flows that are unsafe to measure on these flashy streams.

The precipitation patterns in Indiana, PA have rainfall measured approximately 55% of the days of the year. We therefore only see a seasonal change in the water budget related to evaporation and infiltration on low flow (low precipitation) days. During large rainfall events, most of the water falling on the land surface is entering either the stormwater or stream system, and sometimes both.