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.

Lower Salinas River Watershed: Nutrient TMDL Project Area

Background

Pollution of surface and groundwaters from nitrate and unionized ammonia has been long standing problem for the lower Salinas Valley. Monitoring data in the Lower Salinas River Watershed suggest 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 known to be a potential driver of algal blooms occurring immediately after something called a "first flush" event, which is 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.

Location

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 303(d) listed water bodies:

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

Summary

The TMDL for Lower Salinas River Nitrogen Compounds and Orthophosphate 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. Lower Salinas River Watershed water quality is monitored through the Central Coast Ambient Monitoring Program (CCAMP). CCAMP Water Quality objectives for Dissolved oxygen, Cholorphyll-a, and microsystin align with Basin Plan numeric water quality objectives.

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]

Water Quality Monitoring

The Central Coast Regional Water Quality Control Board (RWQCB) 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 CMP.

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

Status of Nitrate

The Old Salinas River at Monterey Dunes Way is the only monitoring site in the Lower Salinas River Watershed that has decreasing levels of Nitrate

2016 Levels of Nitrate

Status of Un-ionized Ammonia

Status of Orthophosphate

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

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.