Skip to main content

Applicability and Lessons Learned from Using the Load Duration Curve Method to Develop TMDLS for Hardness-dependent Metals

Buy Article:

$17.50 plus tax (Refund Policy)

Or sign up for a free trial

A load duration curve (LDC) is a graphic representation of the assimilative capacity of a water body at a full range of flow regimes. The LDC is frequently used to represent the Total Maximum Daily Load (TMDL) of a given pollutant or constituent for the watershed draining into the impaired water body. This article draws TMDL examples from approximately two dozen TMDLs developed for impaired water bodies within the Neosho River and the Lower Arkansas River basins, Kansas USA, and focuses on how different challenges posed by various watersheds can be met using the LDC method. Specifically, this article describes how the LDC method is applied to multiple watersheds with hardness-dependent metals impairment. Even when key challenges arise such as disparities in data availability, stream or river flow characteristics, or hardness-flow relationships, these environmental factors may be effectively incorporated into the LDC developed for each watershed to yield an implementable TMDL for the hardness-dependent metal(s) in question. This article demonstrate how the LDC approach may be used to calculate waste load allocations for point source discharges, load allocations for non-point discharges, and explicit or implicit margins of safety required to ensure adequate protectiveness of the watershed. The selection process for hardness values (single values and/or regression-derived equations) to be integrated into the TMDL water quality target at specific flow percentiles is also discussed in this article. Modifications that are occasionally required when a stream is intermittent and/or dominated by point source discharge flow are presented and explained as well. Discharge monitoring data from point sources are sometimes limited and example modifications to waste load allocation and current point source load calculations for watersheds with or without discharge monitoring data for specific point source discharges are discussed. TMDLs that apply to sub-watersheds within a watershed are complicated by differences between hardness on the tributaries and main stem. These differences are addressed through LDC displays segregating relative contributions from each tributary. Point source and non-point load reductions are critically important in implementing the TMDL, and this article provides examples of how point and non-point load reductions will be calculated depending on data availability. For example, in cases where site-specific water quality data is limited, the LDC may be integrated with a Generalized Watershed Loading Function or other hydrodynamic model to estimate non-point loading to the watershed. The discussion also addresses the various working assumptions, uncertainties, and examples of implicit and explicit margins of safety required to develop and implement an achievable TMDL for hardnessdependent metals.
No Reference information available - sign in for access.
No Citation information available - sign in for access.
No Supplementary Data.
No Data/Media
No Metrics

Keywords: HARDNESS-DEPENDENT; LOAD DURATION CURVE; METALS; TMDL

Document Type: Research Article

Publication date: 2007-10-01

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
X
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