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South Orange County

Watershed Management Area (WMA)

Photography By: Brianna Martin, Francesca DeLeon and Minell Enslin.

Overview

The San Juan Hydrologic Unit (SJHU) encompasses a land area of 496 square miles within the borders of Orange, San Diego, and Riverside Counties, with approximately 70 percent of the area located in Orange County and 30 percent in San Diego County. The South Orange County (South OC) Watershed Management Area (WMA), also referred to as the San Juan WMA, includes the area that encompasses the SJHU as defined in the Water Quality Control Plan of the San Diego Basin. The South OC WMA is located in the northwestern corner of the San Diego Regional Water Quality Control Board's (RWQCB) jurisdiction.

The SJHU is divided into five distinct hydrological areas (HA) listed below:

  • Laguna (901.1)
  • Mission Viejo (901.2)
  • San Clemente (901.3)
  • San Mateo Canyon (901.4)
  • San Onofre (901.5)

Four of these HAs are within the South OC WMA (901.1 - 901.4) and two are within the jurisdiction of San Diego County (901.4 - 901.5). Additionally, the Permit allows the larger hydrologic unit to be separated into sub-watersheds to focus water quality prioritization and jurisdictional runoff management program implementation efforts. The SJHU is comprised of six subwatersheds, listed below:

  • Laguna Coastal Streams Watershed
  • Aliso Creek Watershed
  • Dana Point Coastal Streams Watershed
  • San Juan Creek Watershed
  • San Clemente Coastal Streams Watershed
  • San Mateo Creek Watershed

The cities shown in the image above, in addition to unincorporated Orange County and Orange County Flood Control District, (collectively the Copermittees) are responsible for operating an interconnected storm drain system in the South OC WMA which discharges stormwater and urban runoff pursuant to the National Pollutant Discharge Elimination Systems (NPDES) Municipal Separate Storm Sewer Systems (MS4) Permit. RWQCB administers the MS4 Permit for the San Diego Region.

South OC climate is typically dry from May through October and rainy from late October through April. In the SJHU, the South OC WMA has a population of about 550,000, and San Diego County has a population of about 25,000. The vast majority of the population is concentrated in the more developed urban and suburban coastal regions of Orange County, which bears a disproportionate share of the water quality concerns when compared to other SJHU areas. The South OC WMA is working to address these concerns, which have the potential to impact how residents, business owners, and tourists use and interact with local water bodies. Many of the water bodies support multiple beneficial uses, including those outlined in the table below.

For more information about water bodies see the San Diego Basin Plan, which provides information on uses of water bodies and water quality objectives, beneficial uses and the 303(d) list, which identifies water body segments not meeting water quality standards.

Water Quality Improvement Plan (WQIP)

  • South Orange County (SOC) Water Quality Improvement Plan (WQIP)

When excessive quantities of pollutants are deposited into these water bodies, they may inhibit many or all of these beneficial uses and can result in actions such as beach closures and postings.

To address these pollutants, Copermittees are required to develop a comprehensive Water Quality Improvement Plan (WQIP) for the WMA that identifies highest priority water quality conditions, strategies to address them, and monitoring plans. The WQIP and associated Annual Reports are required by the MS4 Permit (Order No. R9-2013-0001, as amended by Order Nos. R9-2015-0001 and R9-2015-0100) and focus on improving the quality of stormwater and non-stormwater discharges by Copermittees’ MS4s. Lacking outfalls in the SJHU, the County of San Diego has allowed Orange County Copermittees to lead WQIP efforts for the SJHU.

On June 20, 2018, the RWQCB accepted South OC WMA's proposed WQIP for the SJHU. South OC WMA Copermittees have chosen to focus treatment on the following three high priority water quality conditions:

  • Pathogens at beaches
  • Unnatural water balance/flow regime in stream reaches and coastal estuaries
  • Channel erosion/geomorphologic impacts and erosion in stream reaches

Based on the proposed long-term strategic vision, short-term strategies, optional strategies and clear milestones to trigger these strategies, it is reasonable to expect that this WQIP will result in significant improvement of beneficial uses in receiving waters.

For more information, please visit the Data Clearinghouse for the South OC WMA MS4 Copermittees at https://ocgov.box.com/v/SDR-WQIP-Clearinghouse.

Click here for education and outreach information.

WQIP Annual Reports

  • Annual Reports

Jurisdictional Runoff Management Plan

  • Jurisdiction Runoff Management Program (LIP) Documents
  • GIS Data

BMP Design Manuals

  • BMP Design Manuals

Other Plans and Projects

  • Reports and Special Studies
  • Water Quality Data

Things To Consider

When excessive quantities of pollutants are deposited into these water bodies, they may inhibit many or all of these beneficial uses and can result in actions such as beach closures and postings.

To address these pollutants, Copermittees are required to develop a comprehensive Water Quality Improvement Plan (WQIP) for the WMA that identifies highest priority water quality conditions, strategies to address them, and monitoring plans. The WQIP and associated Annual Reports are required by the MS4 Permit (Order No. R9-2013-0001, as amended by Order Nos. R9-2015-0001 and R9-2015-0100) and focus on improving the quality of stormwater and non-stormwater discharges by Copermittees’ MS4s. Lacking outfalls in the SJHU, the County of San Diego has allowed Orange County Copermittees to lead WQIP efforts for the SJHU.

On June 20, 2018, the RWQCB accepted South OC WMA's proposed WQIP for the SJHU. South OC WMA Copermittees have chosen to focus treatment on the following three high priority water quality conditions:

  • Pathogens at beaches
  • Unnatural water balance/flow regime in stream reaches and coastal estuaries
  • Channel erosion/geomorphologic impacts and erosion in stream reaches

Based on the proposed long-term strategic vision, short-term strategies, optional strategies and clear milestones to trigger these strategies, it is reasonable to expect that this WQIP will result in significant improvement of beneficial uses in receiving waters.

For more information, please visit the Data Clearinghouse for the South OC WMA MS4 Copermittees at https://ocgov.box.com/v/SDR-WQIP-Clearinghouse.

Click here for education and outreach information.

Hydrologic Area (HA) Descriptions

Salt-Creek-Beach_SJHU_LHA_DPHSA_1.14-1200x798

The Laguna Hydrological Area is entirely within the boundaries of Orange County.

Laguna HA (901.1)

Laguna HA (901.1)

Salt-Creek-Beach_SJHU_LHA_DPHSA_1.14-1200x798

The Laguna Hydrologic Area is entirely within the boundaries of Orange County. It encompasses 39,894 acres and is divided into three subwatersheds: Laguna Coastal Streams; Aliso Creek; and Dana Point Coastal Streams. The Laguna Coastal Streams Watershed includes portions of Aliso Viejo, Laguna Beach, and Laguna Woods and consists of the Laguna Canyon Creek watershed, which runs directly down the middle of this watershed and discharges into the Pacific Ocean in Laguna Beach, and several other smaller watersheds.

The Aliso Creek Watershed includes portions of Aliso Viejo, Dana Point, Laguna Beach, Laguna Hills, Laguna Niguel, Laguna Woods, Lake Forest, and Mission Viejo. Its main water body is Aliso Creek, a long, narrow coastal canyon which has headwaters in the Cleveland National Forest and discharges into the Pacific Ocean at Aliso Beach.

The Dana Point Coastal Streams Watershed includes portions of Laguna Beach, Laguna Niguel, and Dana Point. Its main tributary is Salt Creek, which ultimately drains into the Pacific Ocean near the northern boundary of the City of Dana Point. The Dana Point Harbor is also located within this watershed.

Mission Viejo HA (901.2)

The Mission Viejo Hydrologic Area is entirely within the boundaries of Orange County. It encompasses 101,279 acres and represents the San Juan Creek Watershed. The largest of the region's watersheds, the San Juan Creek Watershed includes portions of Dana Point, Laguna Hills, Laguna Niguel, Mission Viejo, Rancho Santa Margarita, and San Juan Capistrano. Its main tributary, San Juan Creek, originates in the Santa Ana Mountains district of the Cleveland National Forest.

San Clemente HA (901.3)

San-Clemente-Sunset_SCHA_1.30-1200x800 (1)

The San Clemente Hydrologic Area is located in the southernmost part of Orange County. It encompasses 12,597 acres and represents the San Clemente Coastal Streams Watershed. The San Clemente Coastal Streams Watershed includes portions of San Clemente, San Juan Capistano, and Dana Point. Prima Deshecha Canada is one of two main streams that flow through the City of San Clemente, ultimately discharging into the Pacific Ocean at Poche Beach. The second main stream draining the watershed is Seguna Deshecha Canada, which discharges into the Pacific Ocean at North Beach.

San Mateo Canyon HA (901.4)

The San Mateo Canyon Hydrologic Area is divided up amongst the Counties of Riverside, Orange, and San Diego. Headwaters for the system are located in Riverside County; however, it drains runoff from all three counties before discharging to the Pacific Ocean in San Diego County. Approximately 31,000 acres of the system lies within the borders of San Diego County.

Of the portion that is within San Diego County, approximately fifty-three percent (53%) is incorporated into Marine Corps Base Camp Pendleton. The remaining portions are unincorporated and include some park lands and other open spaces.

The primary water body within the system of course, is San Mateo Creek. It is fed by a number of smaller creeks and tributaries, including Christianitos Creek. Water bodies within the San Mateo Hydrologic Area have fortunately avoided many of the water quality issues that are present in many developed watersheds, and as such, have avoided any 303(d) listings.

San Onofre HA (901.5)

The San Onofre Hydrologic Area is completely within the boundaries of the County of San Diego. It encompasses approximately 37,500 acres near the northern border of the County and is dedicated primarily to military uses associated with Marine Corps Base Camp Pendleton. In fact, only about three percent (3%) of the land within the hydrologic area is not military land.

The system contains a number of important water features, including San Onofre and Jardine Creeks. These creeks, along with their associated tributaries, converge in San Onofre Valley before discharging into the Pacific Ocean. Similar to the San Mateo Canyon Hydrologic Area, the San Onofre Hydrologic Area has largely avoided the impairments that plague more developed watersheds.