Climate Change Effects on Forests, Water Resources, and Communities of the Delaware River Basin

Abstract

The Delaware River provides drinking water to 5 percent of the United States, or approximately 16.2 million people living in 4 states, 42 counties, and over 800 municipalities. The more than 1.5 billion gallons withdrawn or diverted daily for drinking water is delivered by more than 140 purveyors, yet constitutes less than 20 percent of the average daily withdrawals. Approximately 64 percent of the water withdrawal is used for thermoelectric cooling, a primarily non-consumptive use. The main stem of the Delaware River is free-flowing, such that permitted water withdrawal and discharge depends on weather- related flow conditions. Low flows can limit power generation based on in-stream temperature limits, and can also result in the salt line reaching water intakes in the 133 mile tidally-influenced portion of the river. High flows can damage facilities and cause exceedance of drinking water standards. Source water areas of the Delaware River Basin (DRB) are primarily forested (>75 percent), accounting for the relatively high existing water quality, and contributing to attenuation and reduction of flows. These areas are predominantly in private ownership, and in recent years have been among the areas of the Basin experiencing the fastest population growth. Development of private lands and associated changes in forest cover, impervious surface and floodplain encroachment are of concern. Modeled climate-related changes in timing, type, and intensity of precipitation are also concerns. The diversity in types of water use within the DRB corresponds with a variety of types of risk imposed by changes in climate and land cover. Common Waters, a partnership of close to fifty organizations is piloting strategies to avoid and adapt to changes affecting forests and water resources that are predicted to occur with climate change. This paper discusses predicted climate changes for the Delaware River Basin and what they imply for the importance of forests and water resources, and presents two case studies: a source water protection program for landowners and a climate adaptation plan for the Upper Delaware River Basin. These efforts in the Delaware River Basin could be models for watersheds with highly diverse types of use and complex regulatory systems.