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Next Steps
Table of Contents
Allocation modeling and the process of allocating loads and wasteloads is a component of TMDL development. The steps for TMDL development include:
- Problem identification
- Identification of water quality indicators (e.g., pollutant) and targets (e.g., criteria)
- Source assessment
- Assessment of the linkage between sources and targets
- Allocation of loads and wasteloads
- Follow-up monitoring and evaluation plan
- TMDL assembly
TMDL development can be described as an iterative process, capable of acknowledging and incorporating new information. More information about the TMDL process and the watershed approach is available.
Load and wasteload allocation modeling results, in addition to other watershed information, may suggest that current water quality standards (i.e., criteria and designated uses) are:
- Attainable under a variety of different management strategies and allocation scenarios,
- Attainable under a limited number of management strategies at potentially high cost, or
- Not attainable.
If water quality standards are attainable under a variety of different abatement strategies, then it may be prudent to consider cost-sharing or trading program to provide a means of implementing the most cost-effective combination of point and nonpoint source controls. More information about funding and trading is available.
If it is suspected that standards are not attainable due to natural biological/physical/chemical limitations, irreversible man-made factors, or economic reasons, then a use attainability analysis (UAA) can be conducted to analyze these factors and confirm nonattainability. The UAA is used to substantiate a change in designated uses and corresponding standards, and allocation modeling results may help support UAAs.
A "variance" is a temporary reprieve from current standards, allowing more time to determine (1) if the applicable water quality standards are attainable or (2) if a modification to the standards (i.e., use or criteria) is warranted. A variance should be used when the state believes that the standard can ultimately be achieved, but more time is needed to reach attainment. More information about water quality standards, UAAs, and variances is available in EPA's Water Quality Standards Handbook: 2nd Edition (EPA-823-B-94-005a) and other support documents for standards and criteria.
Additional Information
Additional examples of other frameworks or decision-making tools that can be applied to allocation problems is available through other organizations and research centers. Examples include:
- US Army Corps of Engineers: IWR-PLAN Decision Support Software
. USACE provides free software for doing cost-effectiveness and incremental-cost analysis. IWR-PLAN has been used to compare the incremental environmental outputs or benefits gained with successively more expensive ecosystem restoration plans. - National Center for Environmental Decision Making Though this site is no longer active, it can still contains information about tools, guidance and case studies regarding environmental decision-making.
Numerous other references to optimization and/or risk analysis tools and methods can be obtained from academic and research association sites.