Schuylkill River Hydrology and Consumptive Use Blue Marsh Reservoir, Berks County, PA Report Produced by the City of Philadelphia Water Department March 2010 This page left intentionally blank Executive Summary PWD Objective The Philadelphia Water Department’s (PWD) Source Water Protection Program is responsible for tracking and analyzing trends in water quantity and quality of the two sources of drinking water for the City of Philadelphia. A critical part of the program’s water quantity focus is to investigate the current and future water use patterns, how climate change may influence the drinking water supply, and what the balance is between the needs of the power sector, drinking water supply, aquatic communities, and recreational interests. Ultimately, PWD needs to know how upstream consumptive use impacts drinking water availability to the City of Philadelphia. In order to prioritize research and study interests to obtain this information, there are two critical questions that PWD addresses in this analysis: Is there enough water to meet current needs? What are the current competing water needs in the Schuylkill River? By answering these questions, the Schuylkill River Hydrology and Consumptive Use Analysis is a first step towards identifying the factors that influence the quantity of drinking water available to Philadelphia from the Schuylkill River. Preliminary observations of consumptive use and hydrology are made, and critical future studies are identified. The work presented here builds upon work done by the Pennsylvania Department of Environmental Protection (PADEP) in the Act 220 studies because it focuses solely on the Schuylkill River as a drinking water supply to Philadelphia. Scope of Work The Schuylkill River Hydrology and Consumptive Use Analysis has three parts: I. A hydrological comparison of streamflow gauges is performed to identify which gauge is most representative of drinking water available to Philadelphia. This gauge is then used to determine if the Schuylkill River is providing the maximum Philadelphia demand 100% of the year. II. Consumptive use in the Schuylkill River upstream of the Philadelphia border is estimated by taking the difference of total withdrawals and discharges. Data for this calculation was obtained from PADEP and the Delaware River Basin Commission (DRBC). There are methodological differences between this analysis and Act 220 which are noted in each section and summarized in the Appendices. III. The PWD daily average withdrawal from the Schuylkill River intakes is added to the upstream consumptive use to calculate total consumptive use. Total consumptive use is then compared to the metric that PWD uses to define watershed-wide water stress; a consumptive use greater than 50% of the pre-development 1 in 25 year annual average baseflow (a statistic that represents the lowest average baseflow for an entire year that occurs approximately once every 25 years). i Observations The streamflow gauge at Fairmount Dam does not represent drinking water availability to PWD. The streamflow gauge at Norristown was observed to be the most representative of Schuylkill River drinking water availability to the City of Philadelphia. In the summer, the Schuylkill does not provide Philadelphia’s maximum demand 100% of the time. Two percent of the time, the maximum demand of 286 CFS can not be provided by the Schuylkill River. When a hypothetical pass-by requirement of 100 CFS is added onto the maximum demand and compared to availability, the Schuylkill River can not provide this flow (386 CFS) 6% of the time. The Schuylkill River is approaching water stress conditions. Combined upstream consumptive use and downstream consumptive use total 42% of the 1 in 25 year annual average baseflow, which implies the Schuylkill River is approaching a water stress situation. The upstream consumptive use is 22% and the downstream consumptive use is 20% of the pre- development 1 in 25 year annual average baseflow. Wastewater can compose up to 60% of the streamflow of the Schuylkill River. The total Schuylkill River watershed wastewater discharge was calculated to be 210 CFS. During dry conditions when the streamflow approaches the current 7Q10 flow rate at Norristown, the Schuylkill River water approaching Philadelphia is 60% treated wastewater for more than a week at a time. On some days, the Schuylkill River water approaching Philadelphia is over 90% treated wastewater. The impacts of such large quantities of discharged treated wastewater are not fully understood. Upon identification of the significant presence of treated wastewater in the drinking water supply, PWD will begin investigating any drinking water quality and quantity implications. Downstream drinking water, ecological, and recreational needs must be considered in Blue Marsh Reservoir operational policies. The analysis has observed that the Schuylkill River is approaching a water stress situation, even with the beneficial releases of Blue Marsh reservoir to repel the salt front. PWD would like to see downstream drinking water, ecological, and recreational needs incorporated into the release goals of Blue Marsh Reservoir. ii Schuylkill River Hydrology and Consumptive Use Philadelphia Water Department Table of Contents Executive Summary ............................................................................................................................. i Table of Contents ............................................................................................................................. iii List of Figures ...................................................................................................................................... v List of Tables ...................................................................................................................................... vi Section 1 Introduction .................................................................................................................. 1 Section 2 Philadelphia Water Department ............................................................................... 3 2.1 Philadelphia Potable Water Demand ........................................................................... 4 2.2 Source Water Assessments and Protection Plan ........................................................ 6 Section 3 Hydrology ................................................................................................................... 11 3.1 Low Flow Conditions .................................................................................................... 11 3.1.1 Total Schuylkill River Baseflow Calculation ......................................................................... 11 3.1.2 Sub-Watershed Baseflow Calculation .................................................................................... 13 3.1.3 Low Flow Observations ........................................................................................................... 15 3.2 Upstream Conditions .................................................................................................... 18 Section 4 Water Budget Methodology ..................................................................................... 25 4.1 Potable Water Supply .................................................................................................... 25 4.1.1 Private Domestic Wells ............................................................................................................ 25 4.1.2 Surface and Groundwater Potable Supplies ......................................................................... 28 4.2 Wastewater ...................................................................................................................... 34 4.2.1 Wastewater Treatment Plant Discharge ................................................................................ 34 4.2.2 Septic System Discharge .......................................................................................................... 36 4.3 Agriculture ...................................................................................................................... 41 4.3.1 Processing .................................................................................................................................. 41 4.3.2 Livestock .................................................................................................................................... 42 4.3.3 Irrigation .................................................................................................................................... 43 4.4 Mining .............................................................................................................................. 46 4.5 Golf Courses ................................................................................................................... 46 4.6 Power ................................................................................................................................ 47 4.7 Industry ............................................................................................................................ 49 4.8 Miscellaneous ................................................................................................................. 51 4.9 Self-Supplied Commercial and Industrial ................................................................ 53 Section 5 Water Budget Upstream of Philadelphia .............................................................