Lower San Diego Hydrologic Area (907.1)
Of the HAs located within the San Diego River Watershed, the Lower San Diego Hydrologic Area (907.1) is the most urbanized and suffers from the most pronounced water quality problems. At roughly 110,000 acres, it is also the largest and represents approximately forty percent (40%) of the watershed. Due to its geographic extent, oversight of the storm drain systems within the Lower San Diego Hydrologic Area falls on a number of copermittees: namely, the County of San Diego in combination with the Cities of Santee, El Cajon, La Mesa, and San Diego.
Typically, surface runoff within the basin drains into the San Diego River and is subsequently discharged directly into the Pacific Ocean at Ocean Beach. At the point where the San Diego River meets the Pacific Ocean lies a 37 acre wetland, Famosa Slough, which is managed by the City of San Diego. In addition, the Lower San Diego Hydrologic Area is home to Lake Murray, one of a few major reservoirs within the San Diego River WMA.
The Lower San Diego Hydrologic Area is significantly more developed than its counterparts upstream. Here, undeveloped and open lands make up roughly forty-three percent (43%) of the land area, followed closely by residential uses at thirty percent (30%).
Due to extensive anthropogenic modifications to the environment associated with urbanization, several native plant and animal species commonly found in the Lower San Diego Hydrologic Area have been put at risk of endangerment. A number of threatened and endangered species have been observed here, including the coastal California condor, the great grey owl, the horned lizard, and the kangaroo rat.
The Lower San Diego system consists of a number of water bodies that are listed as impaired under Section 303(d) of the Clean Water Act. Several of the water bodies listed as impaired include Alvarado Creek, Lower San Diego River, Forester Creek, and Lake Murray. These water bodies are impacted by pollutants such as fecal coliform, enterococcus, selenium, nitrogen, manganese, phosphorus, total dissolved solids, and low dissolved oxygen.
Which community is closest to the point at which the San Diego River meets the Pacific Ocean?
San Vicente Hydrologic Area (907.2)
At roughly 47,000 acres, the San Vicente Hydrologic Area is the smallest drainage basin within the San Diego River WMA and has a considerable share of undeveloped land. With the exception of some Native American tribal lands, the entirety of the San Vicente Hydrologic Area lies within the jurisdiction of the County of San Diego.
All of the surface water here flows into and is impounded within San Vicente Reservoir. However, underground aquifers also contribute significantly to the local water supply. Water agency supply records and population data indicate that hundreds of private groundwater wells exist in the San Vicente Hydrologic Area alone.
In recent years, the San Vicente sub-watershed has seen continued human expansion that exerts increasing pressure on the surrounding habitat and ecosystems. Some examples of threatened and endangered species that are known to occur in the San Vicente Hydrologic Area are the Encinitas baccharis, the arroyo toad, and the bald eagle.
Land uses in this portion of the WMA tend to be more variable that in other areas. One of the most recent figures estimates that the San Vicente HA is made up primarily of lands that are undeveloped or open spaces, at sixty-five percent (65%) of the total area. Residential land uses follow, constituting approximately sixteen percent (16%) of the HA. A portion of the sub-watershed is also allocated Native American Reservation land and lies outside of the jurisdiction of typical copermittees.
The San Vicente sub-watershed is home to a couple of water bodies that are listed as impaired under Section 303(d) of the Clean Water Act. For example, San Vicente Creek and San Vicente Reservoir have been listed as impacted by a number of pollutants, including nitrogen, chloride, sulfates, and elevated aquatic toxicity and pH levels.
What threatened and endangered species have been observed in the San Vicente Hydrologic Area?
El Capitan Hydrologic Area (907.3)
El Capitan Hydrologic Area is located just south of the Boulder Creek and San Vicente Hydrologic Areas and covers a land area of about 56,000 acres. It lies primarily within the jurisdiction of the County of San Diego; however, the portion of the sub-watershed within the Capitan Grande Reservation is outside of the jurisdiction of the County of San Diego.
The hydrologic area receives significant runoff from the community of Alpine through Chocolate and Peutz Valley Creeks. All surface runoff, however, is eventually directed into El Capitan Reservoir, a water body that was created by damming San Vicente Creek in 1935. Prior to completion of the San Vicente Dam Raise Project in 2015, El Capitan Reservoir had the greatest storage capacity of any reservoir in the City of San Diego reservoir system. In order to satisfy demand, reservoir supplies are supplemented by groundwater sourced from local aquifers.
Like its neighbor hydrologic areas, the El Capitan system contains vast tracts of undeveloped land, including portions of the Cleveland National Forest. In fact, about eighty-seven percent (87%) of its land area is currently undeveloped land or open space, and only nine percent (9%) of the hydrologic area is being utilized for residential land uses. The remaining land area is divided between other miscellaneous uses.
Unfortunately, El Capitan Lake has been identified under Section 303(d) of the Clean Water Act as impaired for pollutants including manganese, phosphorus, nitrogen, and pH. Urban runoff is considered the most substantial contributor of many of these constituents.
When was El Capitan Reservoir established?
Boulder Creek Hydrologic Area (907.4)
Known as the headwaters, the Boulder Creek Hydrologic Area begins with William Heise County Park and Cuyamaca Rancho State Park in the east and extends westward to encompass a region of approximately 63,000 acres. Although the County of San Diego has been identified as the only copermittee within the hydrologic area, the Inaja and Cosmit Indian Reservation constitutes a large part of the basin. As federal lands, however, the Reservation is not subject to the same requirements as those lands under County jurisdiction.
Primary water bodies in the system include Boulder Creek and Cuyamaca Reservoir, a lake located near the eastern border of the WMA. Almost all water in the Boulder Creek Hydrologic Area originates from the melting of seasonal snow cover. As such, the flow rate of creeks and rivers in the system and downstream varies immensely depending upon the season. Low-flow conditions in the system typically occur from October to March. High-flow conditions, on the other hand, generally occur between May and July, peaking in June. These waters typically have very low concentrations of dissolved solids, alkalinity, and nutrients compared to downstream waters. Surface waters frequently have near-neutral pH values, and dissolved oxygen is at or near saturation.
Encompassing large tracts of the Cleveland National Forest, land use is in the hydrologic area is dominated principally by undeveloped lands and open space, making up about eighty-eight percent (88%) of the sub-watershed area. The remainder of the land is distributed between residential uses (7%), agricultural uses (3%), and other uses.
Experiencing minimal effects on water quality due to development, water bodies within this region of the management area have largely escaped water quality issues that are more prevalent in portions of the watershed downstream.
Which Reservation is located within the Boulder Creek Hydrologic Area?
“El Capitan Reservoir.” The City of San Diego. The City of San Diego, n.d. Web. <https://www.sandiego.gov/water/recreation/reservoirs/elcapitan>.
San Diego County MS4 Copermittees. 2008. San Diego River Watershed Urban Runoff Management Plan (WURMP). Final, March 2008. Submitted to the San Diego Regional Water Quality Control Board by the San Diego River Copermittees.
San Diego County MS4 Copermittees. 2016. San Diego River Watershed Management Area Water Quality Improvement Plan (WQIP). Final, January 2016. Submitted to the San Diego Regional Water Quality Control Board by the San Diego River Copermittees. Prepared by Larry Walker and Associates and Amec Foster Wheeler Environment & Infrastructure, Inc. for the San Diego County MS4 Copermittees: California Department of Transportation, City of El Cajon, City of La Mesa, City of San Diego, City of Santee, County of San Diego.
San Diego Regional Water Quality Control Board (San Diego Regional Board). 2016 (August 5). Basin Plan. San Diego, CA. Available: http://www.waterboards.ca.gov/sandiego/water_issues/programs/basin_plan.
State Water Resources Control Board. 2010. California’s 2010 Clean Water Act Section 303(d) List of Water Quality Limited Segments. Approved October 11, 2011. Sacramento, CA: State Water Resources Control Board.
Whether you become involved in the public process or you simply take steps to limit your own water usage in and around your home, you can become a part of the solution.
Think about replacing sod and other water-intensive shrubbery with drought-tolerant landscaping. As a result of the drought, many jurisdictions and water agencies actually offer rebates and other incentives to remove natural turf and install rain barrels and other water capture devices. Not only will this save you money up front, but it will also reduce your monthly water bill! Keep in mind that irrigation runoff from your property is prohibited and can result in a fine.
Limit car washing and power-washing of building exteriors as much as possible. If your vehicle is in need of some TLC, then consider taking it to a certified car wash. If you are on a budget, then wash your car over permeable or unpaved surfaces, allowing any excess water to be absorbed into the soil instead of running into storm drains.
Dispose of pest waste appropriately. When taking your dog for a walk, make sure that you always have a bag on hand so that when nature calls, you are ready. This will help prevent bacteria and pathogens that can cause illness from getting into our waterways.
If you have some free time and don’t mind getting your hands a little dirty, many conservancies and foundations host clean up events for local creeks and lagoons. Please see our calendar to learn more about what events are being offered in your area!
Don’t litter! Trash on our roadways and in our yards has a tendency to make its way to creeks, rivers, and ocean waters during rain events. Even consider carrying a bag with you to collect litter as you take your morning or evening neighborhood stroll.
Implementation and adaptation of the Water Quality Improvement Plan is an ongoing process and as always, public input is encouraged. Meetings that are open to the public are posted in a timely manner to allow for public involvement. If you are interested, please check out our calendar for upcoming meetings.
If you observe any discharges of water that you believe may be illicit, then do not hesitate to report it by means of our pollution reporting page.
And lastly, do what you can to spread the word! Sometimes the most effective strategy is the simplest one. Now that you are a water quality expert, we are relying on your help to educate your coworkers, family, and friends.