Nutrient numeric endpoint analysis for the Klamath River, CA
HERO ID
5432690
Reference Type
Technical Report
Year
2008
Language
English
| HERO ID | 5432690 |
|---|---|
| Year | 2008 |
| Title | Nutrient numeric endpoint analysis for the Klamath River, CA |
| Authoring Organization | Tetra Tech |
| Abstract | The Klamath River in California is listed as impaired for temperature, nutrients, and low DO/organic enrichment. The North Coast Regional Board is developing TMDLs in collaboration with Oregon and USEPA to address these impairments. For TMDL development, Tetra Tech is applying a set of linked simulation models consisting of CE-QUAL-W2 (for reservoirs) and RMA (for free-flowing reaches). The TMDL runs have primarily addressed numeric criteria for DO and temperature. Tetra Tech, under contract to EPA Region IX and the California State Water Resources Control Board also developed an approach for calculating nutrient numeric endpoints (NNE) for use in California Water Quality Programs (Tetra Tech, 2006). The “Technical Approach to Develop Nutrient Numeric Endpoints for California,” referred to as the California NNE approach, is a risk-based approach in which targets are developed for response variables (or secondary indicators) such as algal density. These response targets can then be converted to site-specific nutrient targets through use of modeling tools. The California NNE approach recognizes that there is no clear scientific consensus on precise levels of nutrient concentrations or response variables that result in impairment of a designated use. To address this problem, waterbodies are classified in three categories, termed Beneficial Use Risk Categories (BURCs). BURC I waterbodies are not expected to exhibit impairment due to nutrients, while BURC III waterbodies have a high probability of impairment due to nutrients. BURC II waterbodies are in an intermediate range, where additional information and analysis may be needed to determine if a use is supported, threatened, or impaired. Tetra Tech (2006) lists consensus targets for response indicators defining the boundaries between BURC I/II and BURC II/III. Tetra Tech (2006) also documents a set of relatively simple but effective spreadsheet tools for application in lake/reservoir or riverine systems to assist in evaluating the translation between response indicators and nutrient concentrations or loads. One important use of the NNE is for setting initial nutrient endpoints for waterbodies requiring nutrient TMDLs. Tetra Tech (2007), under contract with USEPA, conducted a case study of potential NNE endpoints on the Klamath River. That study, “Nutrient Numeric Endpoints for TMDL Development: Klamath River Case Study”, addressed only periphyton in the riverine portion of the watershed and used water quality data for 2000-2003, coupled with periphyton observations from 2004. Since that time, significantly more data have become available, and corrections have been made to earlier data. At the request of the North Coast Regional Water Quality Control Board, USEPA has funded this follow-on study. The two major purposes are (1) to extend the NNE analysis to the two reservoirs (Iron Gate and Copco) on the California portion of the Klamath system, and (2) to update the stream periphyton analysis to reflect more recent and corrected data. |
| Is Certified Translation | No |
| Dupe Override | No |
| Is Public | Yes |
| Language Text | English |