Using Traveltime Along Local Streams to Understand Watersheds

Detailed stream flow data and calculations were used to evaluate time-of-travel throughout both of the watersheds that are utilized for the City of Allentown’s surface water sources.

Detailed stream flow data and calculations were used to evaluate time-of-travel throughout both of the watersheds that are utilized for the City of Allentown’s surface water sources.

City of Allentown | Source Water Protection Technical Assistance Program

Allentown, Pennsylvania

The City of Allentown in Lehigh County, Pennsylvania, utilizes multiple sources for their drinking water supply.  Two of the sources are surface water sources on two very different waterways – the Little Lehigh Creek and the Lehigh River.  The Little Lehigh Creek drains approximately 97 square miles of watershed based in limestone-type geology.  The Lehigh River drains approximately 1032 square miles of watershed stretching northward through the local limestone geology, crossing the Blue Mountain, through the Pennsylvania Anthracite region, and ending at the southern edge of the area that has become known as the northern tier.  Because the watersheds are of vastly different size and characteristics, each has unique concerns and potential contamination threats.
Understanding time-of-travel along all the streams and rivers was crucial to prioritizing potential threats to the water supply and creating strategies to manage risk.  

SSM performed technical evaluations were performed on both surface water sources utilizing detailed stream flow data and calculations prepared by the US Environmental Protection Agency and US Geologic Survey.  The water system was provided with detailed mapping showing average time of travel for all stream segments throughout the watersheds.  The mapping can be used to understand the relative threat from various locations in both watersheds including industrial parks, wastewater treatment outfalls, and acid mine drainage.