So what exactly is a watershed (also known as a drainage basin)?
It is simply an area of land, surrounded by mountains or ridgelines around the perimeter, where all water/rain within the basin drains to the center and out to an end body of water, usually the ocean or a lake. Our watershed is called the San Luis Rey Watershed, and it is approximately 562 square miles, covering pretty much all of northern San Diego County.
An easier way to explain this concept is to simply picture a bathtub. This will be our watershed. It’s surrounded by high walls and the lip of the tub (our mountains); no matter where the water falls within the bathtub, it always flows down to the drain. In our case, this drain is the mouth of the San Luis Rey River where it empties into the Pacific Ocean near the Oceanside Harbor. Our watershed is bordered on the north by Palomar Mountain and the Hot Spring Mountains, and other smaller ridgelines to the south. Any rain or pollution that occurs within our watershed will eventually make its way down to the San Luis Rey River and then out to the Pacific Ocean.
So why are watersheds important to us?
Watersheds sustain life in so many different ways. Both the surface and groundwater found within a watershed often provides drinking water to the local communities. The City of Oceanside gets 13% of its drinking water from local groundwater sources, and other communities further east get up to 100% from these same local sources. A healthy watershed provides food and habitat for many different animal species, as well as lovely places for us to hike and explore nature. The climate in the San Luis Rey Watershed has helped to make Fallbrook the avocado capitol of the world for many, many years, and agriculture is still a vital part of the SLR Watershed today, with numerous orchards, groves, and nurseries here.
A watershed is not bound by city limits or roads on a map, and it does not respect political boundaries. Rather it is nature itself that draws these boundary lines in the form of the ridgelines along the edges. And every single person and animal living within the watershed is connected in some way. We’re like one big family unit, and what we do on our own property can affect someone or something (plants and wildlife) that lives downstream from us.
This is why it is so important for us to go out and explore our watershed and take ownership of it; only when we love our watershed will we respect it enough to want to protect our natural resources.