The water that flows through the San FranciscoBay is part of a watershed that covers 40% of California. What is a watershed? A watershed is an area of land over which all water eventually flows to the same point. Starting at the tops of mountains, water flows (usually from melted ice and snow); forming rivers, streams, lakes, groundwater and every other form of water. The major watershed that flows eventually through the Sacramento—San Joaquin River Delta and ultimately out through the Golden Gate may cover 40% of California, but it is the primary source of water for 25 million Californians and 7000 square miles of agriculture. This water is not only important for the humans who live here (who use up to 50% of the water), it is also shared by many delicate habitats that house a diversity of organisms. Some endangered species such as delta smelt, steelhead, and Chinook salmon rely on the San Francisco Bay Delta watershed to survive.
There are many natural and human factors that influence the watershed. As human populations grow, and the demand for food and water expands, more water is taken from the watershed and often redirected to go where it otherwise would not go. Mother nature has a say in how the water flows as well—this year, for example, low amounts of rain and snow will impact us throughout the year as we get less rain now and less snow-melt later on.
We don’t just take water out of the watershed. There is give-and-take of water between humans and the Delta. We take up water to use in our homes, gardens and agriculture, and then much of our wastewater is cleaned and returned to the Delta or recycled for use (usually irrigating parks and public landscaping). Is water the only thing we put back into our watershed? Unfortunately, no. As water flows over the ground it picks up a lot of stuff with it. Water that soaks into the ground and that goes down storm drains is not cleaned or filtered. That means that the fertilizers, soaps (from washing cars outside, for example), and animal waste (from pets and from farms), for example, all enter the very waters that we use to drink!
Our students in the Delta aren’t the only ones learning how to take care of our watershed; MSI is also hosting an Ocean Views Project: Watershed Adventure program that brings students into each part of the watershed in their local area. Check out their progress and watch videos of their experiences with water!
You can make your own watershed at home or in class with this easy activity. What happens when you add creases (diversions) that could represent a man-made canal or aqueduct? Does the same amount of water end up flowing through the original “rivers”?