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Oil can contaminate water and harm birds
Oil spills are caused by human mistakes and carelessness. Usually spills happen when ships carrying large oil tanks sink in the ocean, and the oil leaks out of its containers into the water, killing thousands of marine animals.
To help demonstrate what would happen if oil spilled in the Delta, try this: fill a foil baking pan halfway with distilled water. Add some blue food coloring and mix. Pour small amounts of dark cooking oil into the pan. Use a popsicle stick to move the water back and forth, simulating the motion of a flowing river.
To see how the oil can stick to birds, place a real feather or two in the water for
a minute. Observe what happens to the feathers and write or draw about it.
Look back at 2015...
The Delta includes 57 islands protected by more than 1,100 miles of levees that were built about 150 years ago to prevent flooding of farm lands. Today, those levees also protect hundreds of thousands of people who live and work here. State highways, railroad lines, water, energy and gas pipelines also cross the Delta and rely on the continued stability of the levees. The force of the river and soil erosion contribute to levee deterioration. In the past 100 years there have been more than 160 levee failures that have threatened life, property and also drinking water supplies by allowing seawater from San Francisco bay to enter critical freshwater distribution areas.
In 1870 a wood and iron craft called a clamshell dredge was introduced, making the job of building levees easier to complete than by using hundreds of laborers with hand tools. The clamshell dredge used a bucket that resembled a clamshell to pull sediment from the river floor to use to build up solid barricades, called levees, so that the river did not flood the islands.
For more information on dredging see this website: