Skip to main content


Buy Article:

$9.50 plus tax (Refund Policy)

Or sign up for a free trial

The U.S. Environmental Protection Agency, Region III, recently developed Total Maximum Daily Loads (TMDLs) for the Christina River Basin and Wissahickon Creek to ensure compliance with applicable water quality standards for dissolved oxygen. In both cases, the TMDLs were premised on integrated hydrodynamic, water quality, and sediment contaminant models that evaluated the stimulating effect of nutrients on periphyton growth. The periphyton state variable served as the basis for determining the diurnal range of dissolved oxygen concentrations about the mean daily concentration. A review of the modeling report for the Christina River Basin indicated that the periphyton half-saturation constant for phosphorus was unusually high. Through subsequent review, we determined that the unusual value drove the significant load reductions contained in the TMDL. Furthermore, diurnal dissolved oxygen data collected by the USGS under drought flow conditions demonstrated that the model predictions were inaccurate. The USGS data were presented to EPA and the Agency revised the model, using a more-typical half-saturation constant, to better approximate the observed dissolved oxygen range. A review of the Wissahickon Creek TMDL modeling report indicated that it used a typical phosphorus half-saturation constant for periphyton growth, but most of the other kinetics were not supported by data. Rather, values were selected from typical ranges to match the dissolved oxygen profile. In addition, the model used fixed reaeration rates rather than rates calculated based on hydrodynamic considerations. EPA revised its model to address some of the objections we raised. As a result, one discharger avoided additional regulation on phosphorus.
No Reference information available - sign in for access.
No Citation information available - sign in for access.
No Supplementary Data.
No Article Media
No Metrics

Document Type: Research Article

Publication date: 2005-01-01

More about this publication?
  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

    A subscription to the Proceedings of the Water Environment Federation includes access to most papers presented at the annual WEF Technical Exhibition and Conference (WEFTEC) and other conferences held since 2000. Subscription access begins 12 months after the event and is valid for 12 months from month of purchase. A subscription to the Proceedings of the Water Environment Federation is included in Water Environment Federation (WEF) membership.

    WEF Members: Sign in (right panel) with your IngentaConnect user name and password to receive complimentary access. Access begins 12 months after the conference or event
  • Subscribe to this Title
  • Membership Information
  • About WEF Proceedings
  • WEFTEC Conference Information
  • Learn about the many other WEF member benefits and join today
  • Ingenta Connect is not responsible for the content or availability of external websites
  • Access Key
  • Free content
  • Partial Free content
  • New content
  • Open access content
  • Partial Open access content
  • Subscribed content
  • Partial Subscribed content
  • Free trial content
Cookie Policy
Cookie Policy
Ingenta Connect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more