Mokelumne River and Lodi Lake clearer this year
The water at Lodi Lake and the Mokelumne River is slightly clearer than it was last year, according to results from recent tests.
The tests were conducted by local students under the guidance of Lodi Watershed Coordinator Kathy Grant for the 17th year in a row and Lodi’s findings were added to national results from the 2017 annual Secchi dip-in event.
Locations for testing included north of the boathouse at Lodi Lake, the east end/center of Lodi Lake, and the main channel of the Mokelumne River 500 yards upstream from the Woodbridge Dam. In order to determine the clarity of the water, the students lowered a Secchi disc into the water to determine the depth at which the disc was no longer visible and the water became murky.
The water became murky and the disk disappeared at 6.6 feet at the testing location north of boathouse at Lodi Lake, and 4.9 feet at the east end of the lake. The disc disappeared at 8.2 feet in the Mokelumne River. This compared to last year’s measurements of 4.8 feet at the location north of the boat house, 3.9 feet at the location on the east end of the lake and 5.6 feet in the Mokelumne River.
The results continue to show that the river is clearer than the lake, Grant said. This may be because there is more activity going on in the lake than in the river. The students also discovered that water released from Camanche Dam greatly affects the flows, turbidity and water clarity of the Lower Mokelumne River.
During the winter, the students observed very turbid water because of the rainfall, Grant said.
“There was 100 percent more rainfall than normal and the water looked like chocolate milk,” Grant said. “It was so dark because it was so full of soil that was in the runoff as the watershed drained.”
During the winter, flows were coming out of the Camanche Dam at about 5,000 cubic feet per second. The increased water flows resulted in increased turbidity and sediment loads, Grant said. As of late June, the flows in the Camanche Dam have dropped and water is slowing down due to less rainfall. As flows slowed down the sediment load dropped out and settled, improving water clarity, Grant said.
In order to improve the clarity of the water at Lodi Lake and the Mokelumne River, Grant said people must understand that everybody lives in a watershed, and the streets, sidewalks and other landscapes drain into the river or waterways close to their homes.
“When you see somebody that’s watering their lawn and its flooding the gutter, I know that water is going to the river and it’s carrying with it whatever sediments, soils, fertilizer or pesticides are running off the landscape,” Grant said. “That stuff is what is causing the lake to lose its clarity.”
In an effort to improve water clarity, Grant suggested that residents fix oily and leaky cars, refrain from using leaf blowers, sweep up their front walk way, pick up trash, go to a car wash instead of washing at home and use less water on their landscape to decrease runoff.
Maintaining clarity in the lake and river is important because it’s the law, Grant said.
“The Clean Water Act says we can’t allow the streets of Lodi to drain into the Mokelumne River and then pollute it. That’s illegal,” Grant said.
Grant said water clarity is also important because the city’s drinking water is coming out of the Mokelumne River. Plants and animals also depend on clean water too, she said.