Source Water Protection in An Urbanized Karst Terrain: Examples from the Lehigh Valley

Located in a rapidly developing valley immediately west of the City of Allentown, the Little Lehigh Creek watershed is the focus of many investigations targeting the sustainability of the water resources of the Lehigh Valley.  As in most places, clean and abundant water holds the key to the vitality of the valley.  The Lehigh Valley is home to high quality streams, including several designated Class A trout waters, as well as multitude of groundwater sources that serve as the drinking water supply for the City of Allentown and the Lehigh County Authority.  While many investigations have assessed the water resources of the valley, none have definitively quantified the volume and migration of ground and surface water as it flows from the headwaters to the confluence of the Little Lehigh Creek with the Lehigh River.  The reason for this lies in the complex interaction between surface and ground water.  The interconnection between storm water, stream flow, and groundwater is augmented by prevalence of sinkholes and karst topography within the valley.

In addition to being placed on the Critical Water Planning Area Watch List under the Pennsylvania State Water Plan, the basin of the Little Lehigh Creek is the setting for three source water protection projects under the Pennsylvania Department of Environmental Protection Source Water Protection Technical Assistance Program (SWPTAP).  In an effort to quantify the flow of groundwater feeding the water supply sources, a three-dimensional, hydrogeologic computer model was developed by SSM Group, Inc.  This presentation describes the findings of the computer modeling effort and the implications for source water protection and future water resources planning in the area.