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

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

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

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

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

Nutrients - why are we concerned?

Nutrients - why are we concerned?

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

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

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

An example in the Santa Monica Mountains

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

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

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

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

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

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)

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

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 6 0.155* 0.03* Santa Monica Mtns (mostly Malibu) <2.5 <0.4 ______________________ *USEPA numbers are NO3+NO2 and total P

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

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

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

Contacts/Additional Information Shirley Birosik 213-576-6679 sbirosik@rb4.swrcb.ca.gov www.swrcb.ca.gov/rwqcb4 USEPA - nutrient criteria info www.epa.gov/ost/standards/nutrient.html