Section 1: Introduction
Introduction
The Carlsbad Watershed Management Area (WMA) Water Quality Improvement Plan (WQIP) was prepared by the cities of Carlsbad, Encinitas, Escondido, Oceanside, San Marcos, Solana Beach, Vista, and the County of San Diego (herein referred to as Responsible Agencies (RAs)) in accordance with the San Diego Region National Pollutant Discharge Elimination System (NPDES) Permit and Waste Discharge Requirements for Discharges from the Municipal Separate Storm Sewer System (MS4) Draining the Watersheds Within the San Diego Region (MS4 Permit) under Order No. R9-2013-0001, as amended by Order Nos. R9-2015-0001 and R9-2015-0100. The Carlsbad WMA WQIP was accepted by the San Diego Regional Water Quality Control Board (RWQCB) in November 2016. The WQIP was updated in May 2018 and September 2021 (Carlsbad WMA Responsible Agencies, 2021).
The purpose of the WQIP is to guide the Responsible Agencies’ jurisdictional and watershed efforts, including Jurisdictional Runoff Management Programs (JRMPs), toward achieving improved water quality in storm water discharges and receiving water bodies. The WQIP describes the processes established and the data and information evaluated to prioritize water quality conditions and implementation efforts in the watershed. The current accepted WQIP can be found on the Project Clean Water website.
WQIP Annual Report Overview
This WQIP Annual Report summarizes WQIP implementation during the applicable reporting periods:
- JRMP and WQIP implementation period: July 1, 2022, through June 30, 2023 (Fiscal Year (FY) 23); and
- Monitoring and assessment program period: October 1, 2022, through September 30, 2023.
The objective of the Annual Report is to present the implementation outcomes of the WQIP and corresponding JRMPs, progress toward WQIP numeric goals, and monitoring and assessment program findings (Figure 1). While the MS4 Permit dictates compliance requirements for plan development, implementation, and reporting, the implementation information in this annual report is presented without specific MS4 Permit references for easier readability. Appendix A provides details regarding specific MS4 Permit requirements and their location within the Annual Report for compliance clarity.
WQIP Update
The RAs submitted a revised WQIP in September 2021, and the RWQCB accepted the 2021 WQIP on December 13, 2021. The update focused on the Agua Hedionda HA, specifically to analyze bacteria data concerning the impacts of the beneficial uses (Shellfish Harvesting and Contact Recreation Use) in the Agua Hedionda Lagoon and tributaries (see Section 5.1.1 of this report for more details on the update). This Annual Report reflects implementation efforts of the September 2021 WQIP.
WQIP Annual Report Comment Letter
The RAs received a June 19, 2023, comment letter from the RWQCB, 2021-2022 Water Quality Improvement Plan (WQIP) Annual Report Review: Carlsbad Watershed Management Area (WMA). Appendix B of this report provides the comment letter and RA’s September 6, 2023, response letter. The letter requests the following items to be included in the FY23 CWMA WQIP Annual Report:
- By January 31, 2024, the WQIP Copermittees must assess if the Bight ’23 monitoring program also meets the monitoring requirements for the State Sediment Control Plan required under D.1.e(2) according to the San Diego Water Board’s email sent to all Copermittees dated 1/27/23.
- With the data collected to comply with Resolution R9-2014-0020, by the next WQIP Annual Report due January 31, 2024, the City of Oceanside shall:
- Tabulate all collected monitoring data (2016-2022) into a single Excel spreadsheet format,
- Submit supporting documentation that shows all data collected was uploaded into the California Environmental Data Exchange Network (CEDEN) website,
- Present data trends from 2016-2022 for nitrogen, phosphorus, dissolved oxygen, macro algae biomass and cover,
- Show nitrogen and phosphorus ratios for each month where data was collected between 2016-2022, and
- Analyze/discuss relationships with phosphorus and algae, and nitrogen and algae.
The City of Oceanside responded to this request in the September 6th, 2023 letter, Appendix B, and provides requested data in Attachment 1 of this report.
Carlsbad Watershed Management Area
The Carlsbad WMA is approximately 211 square miles (sq. mi.) and includes six individual hydrologic areas (HAs) in northern San Diego County. The WMA contains the entire cities of Carlsbad, San Marcos, and Encinitas and portions of Oceanside, Vista, Escondido, Solana Beach, and San Diego County unincorporated areas. The WMA is bordered by the San Luis Rey River WMA to the north and the San Dieguito River WMA to the south, Figure 2. The Carlsbad WMA reaches inland nearly 24 miles to just northeast of Lake Wohlford. The maximum elevation of the WMA is approximately 2,400 feet, and it extends to sea level at the Pacific Ocean. Various land uses are present, including residential, commercial, industrial, freeways, agriculture, and vacant/undeveloped areas. About 75% of the land is privately owned. The Carlsbad WMA is the third most densely populated watershed in the San Diego Region.
Carlsbad WMA Waterways and Lagoons
The Carlsbad WMA includes waterways and lagoons that serve as significant cultural, recreational, economic, and environmental resources. These areas provide critical habitats for birds, fish, and plants. Responsible Agencies (RAs) establish and implement programs to:
- Protect, restore, and enhance WMA conditions.
- Have comprehensive WMA and HA planning efforts.
The RAs’ desired outcome for the Carlsbad WMA is to improve water quality conditions of wet weather MS4 discharges and receiving waters, as well as eliminate non-storm water and illicit MS4 discharges through the implementation of storm water programs. These efforts are aligned with the overarching WQIP goal to protect, preserve, enhance, and restore water quality and designated beneficial uses of waterways.
The Carlsbad WMA HAs include Loma Alta, Buena Vista Creek, Agua Hedionda, Encinas, San Marcos, and Escondido Creek, all of which have different discharge points to lagoons or the Pacific Ocean (Figure 3). Due to the impoundment of waters at Lake San Marcos, the San Marcos HA is effectively split into two separate drainage areas:
- The drainage area above Lake San Marcos (also known as Upper San Marcos HA).
- The drainage area below Lake San Marcos (also known as Lower San Marcos HA).
Responsible Agencies within the Carlsbad WMA
The RAs within the Carlsbad WMA include the following eight municipalities:
- City of Carlsbad
- City of San Marcos
- City of Encinitas
- City of Solana Beach
- City of Escondido
- City of Vista
- City of Oceanside
- County of San Diego
Jurisdictional Breakdown of Carlsbad WMA
The WMA composition by jurisdictional land area for each of the six HAs is presented in the following table:
| Watershed (HA No.) | Ultimate Receiving Waterbody(ies) | Size (sq. mi.) | % of WMA | Carlsbad | Encinitas | Escondido | Oceanside | San Marcos | Solana Beach | Vista | County of San Diego |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Carlsbad WMA (904) | Pacific Ocean | 211.5 | 100% | 18% | 9% | 13% | 8% | 11% | 1% | 8% | 32% |
| Loma Alta (904.10) | Loma Alta Slough and Pacific Ocean | 9.8 | 4.5% | - | - | - | 97% | - | - | - | 3% |
| Buena Vista Creek (904.20) | Buena Vista Lagoon and Pacific Ocean | 22.6 | 11% | 19% | - | - | 25% | - | - | 45% | 11% |
| Aqua Hedionda (904.30) | Aqua Hedionda Lagoon and Pacific Ocean | 29.4 | 14% | 41% | - | - | 6% | 5% | - | 24% | 24% |
| Encinas (904.40) | Pacific Ocean | 5.4 | 2.5% | 100% | - | - | - | - | - | - | - |
| San Marcos (904.50) | Batiquitos Lagoon and Pacific Ocean | 59.7 | 28% | 29% | 15% | 5% | - | 33% | - | - | 18% |
| Escondido Creek (904.60) | San Elijo Lagoon and Pacific Ocean | 84.6 | 40% | - | 11% | 29% | - | 4% | 1% | - | 55% |
Note: The percentages and details listed are based on the latest updates and may be subject to changes based on ongoing assessments and revisions.