Lower Salinas River Watershed Nutrient TMDL - Implementation and Monitoring Progress

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A watershed-related topic examined by the ENVS 560/L Watershed Systems class at CSUMB.

Image 1. Lower Salinas River Watershed: Nutrient TMDL Project Area

Summary

In order to achieve water quality standards for multi-use water bodies, the EPA implemented a list of 303(d) listed rivers under Section 303(d) of the Clean Water Act (CWA). Total Maximum Daily Load (TMDL) is the criteria for this list.0

The Lower Salinas River Watershed (LSRW) is listed for Nitrogen Compounds and Orthophosphate. This was first approved March 14, 2013 via a vote by the Central Coast Water Board to amend the Water Quality Control Plan for the Central Coastal Basin. At this point, 72 monitoring sites were established. The numeric targets, report summaries and further information regarding the LSRW can be found at the TMDL for Nutrients in Lower Salinas River Watershed, Monterey County, California page. Lower Salinas River Watershed water quality is monitored through the Central Coast Ambient Monitoring Program (CCAMP).

Background

Pollution of surface and groundwaters from nitrate and unionized ammonia has been a long standing problem for the lower Salinas Valley. Monitoring data in the Lower Salinas River Watershed indicate excessive levels of nitrate, unionized ammonia, and associated nutrient-related problems including, excessive orthophosphate, low dissolved oxygen, toxicity and excess algal biomass.[1] Nitrate loading from the Salinas River has been identified as a potential driver of algal blooms occurring immediately after "first flush" events, the first rain after a period of drought [2]. The California Central Coast Water Board is required under the Federal and State Clean Water Act to protect and regulate beneficial uses of these waters. The Lower Salinas Valley Watershed has a wide range of beneficial uses which are not being supported including aquatic habitat, drinking water supply, groundwater recharge, agricultural supply, and water contact recreation. Water Supply and aquatic habitat constitute the most sensitive applicable beneficial uses requiring the most stringent water quality standards.[3] Development of the Lower Salinas Valley Watershed Nutrient TMDL was intended to reduce and eventually eradicate nitrate pollution for the purpose of human health, the Central Coast Water Board's top priority. The numeric targets, report summaries and further information regarding the LSRW can be found at the TMDL for Nutrients in Lower Salinas River Watershed, Monterey County, California page.

Location

Comprehensive list for the Monterey Bay region: The 303d list of Impaired Waterbodies in the Monterey Bay Region and Monterey Bay Area TMDL Listings - Priorities, Progress, and Documents.

The geographic scope of the TMDL encompasses approximately 405 square miles in the Lower Salinas Valley. Agriculture is the dominant land use in the watershed although urbanized areas are increasing.

The Lower Salinas River Watershed Nutrient TMDL applies to the following 303d listed water bodies:

  • Lower Salinas River & Tributaries:
  • Tembladero Slough & Tributaries:
    • Merrit Ditch
    • Reclamation Canal
    • Alisal Creek
    • Alisal Slough
    • Espinosa Slough
    • Santa Rita Creek
    • Gabilan Creek
    • Natividad Creek
  • Old Salinas River
  • Moro Cojo Slough

Action Taken since TMDL Approval

Initial Implementation

The TMDL is implemented through the Conditional Waiver of Waste Discharge Requirements for Discharges from Irrigated Lands (Ag Order) which clearly requires dischargers implement, and where appropriate update or improve, management practices, which may include local or regional control, treatment practices and changes in farming practices to control discharges, meet water quality standards and achieve compliance. If the discharer fails to address water quality they may be subject to progressive enforcement and possible monetary liability. [2] More information regarding dischagers requirements and expectations can be found on the Conditional Waiver of Waste Discharge Requirements for Discharges from Irrigated Lands (Ag Order) page.

Projects

For complete list, see TMDLs in the Monterey Bay Region of California.

TMDL Projects Currently in Development for the Lower Salinas Valley (2015-2016)


Water Quality Monitoring

The Central Coast Regional Water Quality Control Board (CCRWQCB) has designated Central Coast Water Quality Preservation, Inc (Preservation, Inc.) as the main non-profit entity to conduct the Cooperative Monitoring Program in compliance with the Ag Order (Order no. R3-2012-0011). Under this order every enrolled grower may conduct their own surface water quality monitoring, or participate in the Cooperative Monitoring Program (CMP). Over 99% of growers have opted to participate in the Central Coast Ambient Monitoring Program (CCAMP).

The Central Coast Ambient Monitoring Program (CCAMP) conducts monthly monitoring in the Lower Salinas Watershed in order to conduct trend analysis and detect emerging water quality problems.

The Central Coast Water Board's goal is to have all water bodies meet, or under, target TMDL levels by 2025 Total Maximum Daily Loads for Chlorpyrifos and Diazinon in Lower Salinas River Watershed in Monterey County, California 2011.

Status of Nitrate

The overall target TMDL for Nitrate is 10 mg/L for all receiving waterbodies. During the dry season (May 1st - October 31st) Nitrate should not be over 1.4 - 6.4 mg/L in impaired receiving waters for specific streams. During the wet season nitrate should not exceed 8 mg/L for impaired, receiving streams. [4]

The Old Salinas River, at Monterey Dunes Way, is the only monitoring site in the Lower Salinas River Watershed that have shown decreasing levels of Nitrate. Salinas River at Davis Rd & Tembladero Slough at Monterey Dunes Way have shown an increasing trend of Nitrate.

Image 2. Levels of Nitrate at all CCAMP monitoring sites regulated by the Lower Salinas River Watershed Nutrient TMDL. Geometric mean of Nitrate levels in water bodies regulated by the Lower Salinas River Watershed Nutrient TMDL, data retrieved from CCAMP Central Coast Data Navigator.

Examples of time series data for CCAMP monitoring sites furthest downstream in the Lower Salinas River Watershed.

Image 3. Time series data for Nitrate at Tembladero Slough. Data retrieved from: CCAMP Central Coast Data Navigator: Basic Water Quality.
Image 4. Time series data for Nitrate at Blanco Drain. Data retrieved from: CCAMP Central Coast Data Navigator: Basic Water Quality.
Image 5. Time series data for Nitrate at the Lower Salinas River. Data retrieved from: CCAMP Central Coast Data Navigator: Basic Water Quality.

Status of Un-ionized Ammonia

The target TMDL for un-ionized ammonia is 0.025 mg/L.[4] The majority of the water bodies in the Lower Salinas Valley have an un-iodized concentration mean bellow 0.025 mg/L. CCAMP has identified a monotonic decreasing trend of Ammonia levels at Tembladero Slough at Haro Road.

Ammonia levels have decreased in the Salinas River at Chualar Bridge, the Gonzales River Road Bridge, and Chualar Creek at Chualar River Road.

Ammonia levels have increased in the Old Salinas River at Monterey Dunes Way.

Image 6. Un-ionized Ammonia levels at all CCAMP monitoring sites regulated under the Lower Salinas River Watershed Nutrient TMDL. Geometric mean of un-ionized ammonia levels in water bodies regulated by the Lower Salinas River Watershed Nutrient TMDL, data retrieved from CCAMP Central Coast Data Navigator.
Image 7. Time series data for Un-ionoized ammonia at Tembladero Slough. Data retrieved from: CCAMP Central Coast Data Navigator: Basic Water Quality.
Image 8. Time series data for Un-ionoized ammonia at Blanco Drain. Data retrieved from: CCAMP Central Coast Data Navigator: Basic Water Quality.
Image 9. Time series data for Un-ionoized ammonia at Espinosa Slough. Data retrieved from: CCAMP Central Coast Data Navigator: Basic Water Quality.

Status of Orthophosphate

The target TMDL concentration for orthophosphate is 0.3 mg/L during the wet season (November 1st - April 30th). The dry season target (May 1st - October 31st) depends on the specific waterbody, but target threshold ranges from 0.7 mg/L to 0.13 mg/L. [4] CCAMP has identified a monotonic decreasing trend of Orthophosphate levels at Tembladero Slough at Haro Road.

Over the past year, Orthophosphate levels have decreased in the Salinas River at Chualar Bridge and Chualar Creek at Chualar River Road.

Orthophosphate levels have increased in the past year in the Old Salinas River at Monterey Dunes Way.

Image 10. Orthophosphate levels at all CCAMP monitoring sites regulated under the Lower Salinas River Watershed Nutrient TMDL. Geometric mean of un-ionized ammonia levels in water bodies regulated by the Lower Salinas River Watershed Nutrient TMDL, data retrieved from CCAMP Central Coast Data Navigator.

Examples of time series data for CCAMP monitoring sites furthest downstream in the Lower Salinas River Watershed.

Image 11. Time series data for Orthophosphate at Tembladero Slough. Data retrieved from: CCAMP Central Coast Data Navigator: Basic Water Quality.
Image 12. Time series data for Orthophosphate at Espinosa Slough. Data retrieved from: CCAMP Central Coast Data Navigator: Basic Water Quality.
Image 13. Time series data for Orthophosphate in the Lower Salinas River. Data retrieved from: CCAMP Central Coast Data Navigator: Basic Water Quality.

Links

References

  1. RWQCB Lower Salinas River Watershed Nutrient TMDL Staff Report
  2. 2.0 2.1 Conditional waiver of Waste Discharge Requirements for Discharges from Irrigated Lands
  3. TMDL for Nitrogen Compounds and Orthophosphate in the Lower Salinas River Watershed Factsheed #1
  4. 4.0 4.1 4.2 Lower Salinas TMDL Summary

Disclaimer

This page may contain student work completed as part of assigned coursework. It may not be accurate. It does not necessary reflect the opinion or policy of CSUMB, its staff, or students.