1. Establishing Background Concentrations for Nutrients in a Santa Monica Mountains Watershed
Shirley Birosik
Environmental Specialist
Regional Water Quality Control Board-
Los Angeles Region

2. Presentation Outline The Regional Board and what it does
Nutrients - why are we concerned?
Approaches to regulating nutrients
An example in the Santa Monica Mountains
The status of USEPA nutrient criteria
Next steps

3. The Regional Board Nine Regional Boards - semi-autonomous
Address huge variety of unique water quality issues around the state
Under the umbrella of the State Water Resources Control Board
Collectively enforce the California Water Code and federal Clean Water Act

4. The Regional Board State Board formulates water policy
Regional Boards develop and implement regional water quality objectives as well as implement statewide policies
Regional Boards issue permits and enforcement orders
Regional Boards conduct biennial water quality assessments

5. Nutrients - why are we concerned?
Biennial water quality assessments result in updates of “impaired” waters list
Eight of the ten watersheds in this Region have some level of nutrient impairment
The Los Angeles River, San Gabriel River, Calleguas Creek, Santa Clara River, and watersheds draining into the Santa Monica Bay have the most nutrient impairments

6. Nutrients - why are we concerned?

7. Nutrients - why are we concerned?

8. Nutrients - why are we concerned?
Impairments relating to nutrients involve:
Excessive floating algae
Depressed or widely fluctuating DO
Objectionable odors
Threat to drinking water sources from nitrates
Toxicity to fish from ammonia
Sources include both point and nonpoint as well as natural inputs

9. Factors in Eutrophication
Air temperature
Amount of sunlight (light intensity)
Shading
Type of substrate
Trace compounds
Nutrient
concentrations
Length of “day” (photoperiod)
Flow rate
Other plants
(primary
consumers of
nutrients) pH
Water temperature
Dissolved oxygen

10. Approaches to regulating nutrients
Use established numeric objectives
most are for protection of drinking water
Develop “effects”-based numbers
these would have ecological significance in watershed
often not enough “effects” information available
Determine “background” or reference conditions for the watershed

11. An example in the Santa Monica Mountains

12. An example in the Santa Monica Mountains
Existing numeric objectives were not ecologically relevant
Evaluated effects-based data
nitrate-N, phosphate-P
DO, pH, qualitative algal cover
no chlorophyll a data

13. An example in the Santa Monica Mountains
Increasing NO3-N levels were graphed against other parameters using synoptic data
Parameters included DO, pH, PO4-P
No cut-off point for “effects” could be found

14. An example in the Santa Monica Mountains
Evaluated ten years of phosphate-P and nitrate-N data for background conditions
Frequency histograms were generated for:
year round data
summer only, winter only
above and below the major point source
Results from open space sample sites were used to establish background

15. An example in the Santa Monica Mountains
Frequency histograms
Top graph is from open space/parkland above discharge
Green line - most of the NO3-N values fall below this line; pattern similar for PO4-P
Bottom graph is downstream of discharge
More samples with higher nutrient levels; no obvious clustering

16. An example in the Santa Monica Mountains
Results were fairly consistent with other, smaller, and less developed, Santa Monica Mountains watersheds
However, these numbers are not known to have any particular ecological relevance

17. Status of USEPA nutrient criteria
Ambient water quality criteria recommendations for the rivers and streams in the Xeric West were released in Dec. 2000
An ecoregional approach was used - “RTAGs” were utilized
Used lower 25th percentile of all streams within a region as surrogate for reference population
Criteria developed for two causal variables (N & P) and two early indicator response variables (turbidity and chlorophyll a as phytoplankton)

18. Status of USEPA nutrient criteria
Ultimately, USEPA will publish criteria for nutrients in lakes, reservoirs, rivers, streams, and wetlands in 17 ecoregions
These recommended criteria will be used to support the development of more localized, waterbody-specific state criteria
A guidance manual for developing estuarine/coastal criteria is still under development

19. A Comparison (mg/l) (mg/l) Aggregate ecoregion III 0.025* 0.022*
NO3-N PO4-P
(mg/l) (mg/l)
Aggregate ecoregion III 0.025* 0.022*
Subecoregion * 0.03*
Santa Monica Mtns
(mostly Malibu) <2.5 <0.4
______________________
*USEPA numbers are NO3+NO2 and total P

20. Ecoregion III From:Ambient Water Quality
Criteria Recommendations - Rivers
and Streams in Nutrient Ecoregion III,
USEPA, Dec. 2000

21. Next steps
State will be completing a plan by end of 2001 for developing and adopting criteria
Options available include
use of the USEPA numbers as a starting point for more specific criteria (preferred by USEPA)
use of the USEPA numbers directly
development of criteria through a separate scientifically-defensible approach

22. Next steps
State nutrient teams will look at appropriate waterbody groupings and indicators (periphyton as well as phytoplankton?)
State nutrient criteria must be adopted by end of 2004

23. Contacts/Additional Information
Shirley Birosik
USEPA - nutrient criteria info