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Shedding some light on watersheds

September 7, 2011

Category: A Closer Look

It’s not a piece of farming equipment or something you might see in a neighbor’s backyard. A watershed actually refers to an area of land that collects and contains surface water and drains (or sheds) it off into the same place. Essentially, every bit of land is part of a watershed. So, you’re in a watershed right now.

For example, in California, a watershed could start with melting mountain snow that forms small streams, which eventually flow to a river. However, each watershed system is unique. The United States Geological Survey reports that there are nearly 200 watersheds in California alone.

Watershed health is critical for California’s future and economy. For example, Sacramento’s delta area is considered to have some of the state’s most significant watersheds because they supply one of the most productive farming regions in the world. Delta sources also provide water to the Bay area, central valley and southern California.

California’s communities play a powerful role in regional watershed health because they are ultimately responsible for what ends up in our water supply. For example, agricultural irrigation runoff is a main contributor of gray (dirty) water in rural areas. In urban areas, it can get a little more complicated.

Fresno State professor Steve Blumenshine has led research on watershed health that can help communities manage the quality of our state’s most precious resource. He says you’d be surprised at what ends up in our water supply.

“There are many toxins that can affect water quality in developed areas,” Blumenshine said. “These include sewage, septic tank leaks, chemicals, and common household items including pharmaceuticals.”

In fact, scientists recently detected concentrations of pharmaceutical compounds in 2.3 percent of the California groundwater aquifers they tested. Aquifers are underground water-bearing formations that are capable of yielding enough water to supply peoples’ uses—in this case, drinking water. The scientists discovered compounds including caffeine, codeine, and carbamazepine—a common prescription medication used to treat psychiatric disorders. These medications entered our water system mainly through improper disposal.

Blumenshine says another contributor to poor watershed health is called sedimentation.

“Sedimentation is what happens when water runoff passes over surface areas, and in the process, picks up particles, some of them potentially toxic,” Blumenshine said.

He says that the reason sedimentation is more common in developed areas is because, unlike their rural counterparts, the land doesn’t have a lot of soil and vegetation to absorb water. When it rains, the water instead moves out over concrete, structures, and other smooth surfaces at a faster speed (he also notes that’s why urban areas are more likely to have flash floods). As this happens, the water picks up more sediment and becomes dirty in the process.

The first step to addressing this problem is research. Blumenshine has led studies in both urban and rural areas to pin down the causes of poor watershed health. For example, under his direction, Fresno State graduate student Brett Moore led a study to assess the impact of sedimentation in California’s Madera County. With funding help from the EPA, Department of Water Resources, Central Sierra Watershed Committee, and assistance from mentors and undergraduate students, Moore spent months gathering water samples from a stream and testing their sediments in the lab.

Ultimately, the research and others like it can help planning committees set related policy and answer tough questions. For example, what are the impacts of septic systems on our water supply, and do they outweigh the potential costs for increased waste regulation? Or, could increased toxins be due to poor land management, which causes runoff and sedimentation?

 “As long as our water demand exceeds supply, quality and quantity will be issues,” Blumenshine says. “These questions won’t be going away anytime soon.”


Fresno State student researchers collecting sediment samples to take back to the lab.

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