Water Quality 

Lake Hodges provides a potable, or usable, water source for neighboring  communities and a habitat for many different animals. However, Lake Hodges  didn’t become a lake naturally- it is a man-made water reservoir! Lake Hodges’  water levels are maintained by the Lake Hodges Dam, which was built in 1918.  The dam stops the natural flow of the San Dieguito River, causing it to build up  over time into the lake you see today.  

Human population growth and development throughout San Diego County has led to significant habitat loss and a reduction in watershed ecosystem services.  As water flows through our neighborhoods, it picks up pollution from yards  (fertilizers and pesticides), streets (oil and grease), and walkways (trash and pet  poop), and carries the pollutants down the watershed.  

Today’s polluted water no longer encounters the cleaning services that  wetlands used to provide. Over the past 200 years, nearly 85% of Southern  California’s wetlands have been destroyed. With fewer wetlands, the job for  those that remain is bigger and more challenging. Too much pollution and trash  can overwhelm wetlands’ cleansing abilities and destroy their usefulness. This  disrupts the lives of the plants and animals living there, and ultimately affects the  health of habitats throughout the watershed. 

Ecosystem health is crucial to ecosystem services. Scientists and technicians use  different tests to measure a watershed’s health, just like doctors use different  tests to measure your health. One way to determine the health of a watershed is  to monitor the water quality.

Almost everything we do affects water quality. When the physical, chemical  and biological components of water are altered, it causes the watershed to  become unhealthy. There are several different measurable characteristics of  

water that can give us clues to a watershed’s health including ambient  measurements (temperature, pH and dissolved oxygen) and pollutants (nitrate  and phosphate). As you visit the different sites included in this program, you will  observe and record these measurements to determine water quality and overall  health of the San Dieguito Watershed.  

Since everyone lives in a watershed, everyone affects the quality of the water.  We all have a responsibility to protect our limited freshwater resources and the  ecosystem services they provide. By caring for and protecting our watershed,  we’re helping care for the ocean as well. It’s critical that we keep the water in  our watersheds flowing clean and healthy.