San Diego Watersheds

Watersheds are the ecosystems where we live. If we eliminated the country, state and city political labels, we would see our lives defined by the ecosystems that surround us and the habitats, wildlife and waters within them. Groundwater and surface waters like streams and rivers, and their end points at the ocean or in coastal lagoons, are the life blood for ecosytems. The water quality in them defines the flood control, habitat, wildlife and natural filtering resources and capabilities of a watershed. We have eleven watersheds in the county that drain toward the Pacific Ocean. Read more on these pages about the watershed that you live in.

Coastkeeper has monitored San Diego’s waterbodies since 2000. We use the data collected by our volunteers to identify polluted waters and reduce sources of pollution. San Diego’s local government agencies have limited resources and they monitor infrequently, providing only a snapshot of water quality. Data collected by Coastkeeper volunteers increases the amount available so regulators can assess more comprehensive water resources data to make more effective decisions on how to reduce sources of pollution.

Coastkeeper staff and its crew of trained volunteers (we train more than 100 volunteers each year) currently collect and analyze water samples that are analyzed for basic chemistry, nutrients, bacteria, and toxicity from nine out of 11 watersheds in San Diego County on a monthly basis. To ensure that our data meets the highest quality standards possible, Coastkeeper follows a rigorous quality assurance and control plan and standard operating procedures that have been approved by our state regulatory agencies.

To our knowledge, we are the largest volunteer-based water quality monitoring program in the state. Through this program, we create community involvement and stewardship by educating the public on the importance of good water quality in our coastal and inland waters. It adds the scientific data component to Coastkeeper’s work. We are tremendously grateful to the volunteers and partners who share our passion for keeping our waters clean and healthy.

The map above shows the most recent data we have for each location. The sampling locations are graded on how many constituents exceed regulatory thresholds and by how much those thresholds are exceeded. The sites are graded from excellent to poor and reflect only the most recent month’s data. The grading only factors in those constituents which we measure, and do not take into account other possible indicators of stream health such as habitat quality.

What Does Each Rating Mean?

Excellent: These watersheds are mostly healthy and thriving in their natural state. The majority of indicators are at healthy levels throughout the year.

Good: These watersheds are impacted by pollution but remain more resilient than lower grades. They often have one or two indicators that consistently exceed healthy standards at a low level or at a higher level, but only at certain times throughout the year.

Fair: These watersheds are significantly impacted by pollution. They have two or more indicators consistently exceeding healthy levels.

Marginal: These watersheds are severely impacted by pollution and struggling to survive. They have multiple indicators consistently exceeding healthy levels.

Poor: The large majority of indicators in these watersheds consistently exceed healthy levels by high amounts. Many native species may not be able to survive or reproduce in these conditions.

Ambient Measurments

These measurements are not pollutants themselves, but indicate whether or not there is a problem in the river. Like a doctor checking your pulse, if something is wrong, these measurements will be out of whack. The flora and fauna of our waterways survive within very narrow ranges of these indicators.

What would happen to you if all the oxygen was removed from the air? You would end up flopping around gasping for breath. That’s exactly what happens to the fish and insects that survive underwater when the dissolved oxygen levels get too low. High nutrients (link to nutrients section of the webpage) end up lowering the DO levels through a process called eutrophication. The best way to keep oxygen levels high is to limit the amount of nutrients entering into the creek.
pH measures how acidic or basic the water is. Aquatic organisms like a very narrow range of 6.5 to 8.5 which is pretty neutral. The best way to keep our waters pH neutral is to not dump basic or acidic materials in the storm drains (which you shouldn’t be putting anything but rain in there anyway).
Conductivity is a measurement of water’s ability to conduct electrical currents. Salts are the biggest contributor to high conductivity. Like all of these other ambient measurements, the aquatic flora and fauna like to live within a narrow range of conductivity. The species adapted to freshwater can only live in water with low conductivity, the ocean species in higher conductivity, and the estuary species have all sorts of conducutivities that they have to deal with depending on where they are at in the tidal prism.


People get the nutrients they need to live and grow from the food we eat, in the form of sandwiches and vegetables. Plants get their nutrients from the soil and water, in the form of mostly nitrogen and phosphorus. In the farm or garden, people add these nutrients to encourage robust and healthy plant growth. In the water, however, these nutrients are rarely beneficial.Too many nutrients can cause the algae to grow out of control which will blanket the stream bed or surface with unsightly algae. These mats of algae smothers the bottom or shades the sun from the stream. Once that algae star to die, however, it sinks to the bottom and is decomposed by bacteria. This decomposition strips the water of the dissolved oxygen the aquatic species need to breathe. This process is called eutrophication

Nitrates are a form of nitrogen that are available to plants for uptake. At very high levels, nitrate can be toxic to animals, including humans. Some typical sources of excessive nitrates include fertilizer runoff from residential, agricultural or recreational areas like golf courses; or from detergents getting into the storm drains. The best way you can prevent nitrate pollution in our waters is to limit the use of nutrients in your yard, or better yet rip up your grass and plant native plants that don’t need chemical pollutants to be spread around your house. Rivers flowing through our agricultural areas tend to have high nitrate concentrations.
Ammonia is another form of nitrogen. Ammonia doesn’t stick around very long as it is fairly quickly converted into nitrate. Decomposing waste releases ammonia into the water. We usually find it in low levels in the streams, and extremely high levels usually indicates recent sewage pollution.
Phosphorus is a plant nutrient that is especially important in freshwater. A lot of the time, freshwater streams are phosphorus limited. This means the only thing that is holding back excessive algae growth is a lack of phosphorus in the water. The more phosphorus, the more eutrophic the stream gets. Phosphorus can be naturally occurring through the erosion of rocks, but lawn fertilizers and detergents are common human sources. To prevent phosphorus pollution from getting into our water, limit the use of lawn fertilizers and wash your car at a car wash that treats it’s water.


Coastkeeper monitors bacteria as a way of assessing how safe that water is for human contact. E. coli and Enterococcus bacteria are used as indicators of water contamination by fecal material (‘poop’). These indicator bacteria are not ones that would necessarily make you sick, however they may indicate water contamination by sewage, animal or bird waste. Viruses, protozoa, and other bacteria are difficult and time intensive to monitor, so we monitor easy ones that can show us if these harmful organisms are at dangerous levels. Always pick up your pet’s waste. Pet poop is a huge source of bacteria.


A number of metals are extremely toxic to humans and aquatic organisms. Since dissolved metals can bind tightly to sediments in the water, Coastkeeper monitors only the metals that are dissolved in the water since they are bioavailable and toxic. These metals come from industrial pollution as well as from our car’s oil drips and brake pad dust. Since measuring these low levels of metals requires expensive machinery, we work with Dr. Rick Gersberg at the San Diego State University Graduate School of Public Health. We monitor for cadmium, chromium, lead, nickel, zinc, and copper.

This project is financed under the Safe Drinking Water, Water Quality and Supply, Flood Control, River and Coastal Protection Bond Act of 2006, administered by State of California, Department of Water Resources.