Kesterson Reservoir facts for kids
Quick facts for kids Kesterson Reservoir |
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 Kesterson Reservoir
Location in California
Kesterson Reservoir
Location in the United States
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| Location | Merced County, California |
| Coordinates | 37°15′30″N 120°53′30″W / 37.25833°N 120.89167°W |
| Type | reservoir |
The Kesterson Reservoir is a special area within the San Luis National Wildlife Refuge in California. It used to be a very important resting spot for migratory waterfowl (birds that fly long distances). Kesterson once had 12 large ponds, covering about 1,280 acres. These ponds were used to collect water that drained from nearby farms.
In the late 1900s, Kesterson became famous for a sad reason. Many migratory birds, fish, insects, and plants started dying off quickly. This was caused by too much selenium, a natural element, in the water. The reservoir was closed in 1986. Since then, scientists have been watching the selenium levels closely to make the area safe again.
Contents
What is Kesterson Reservoir?
The Kesterson National Wildlife Refuge is about 18 miles west of Merced County, California. It's part of the larger San Luis National Wildlife Refuge. The refuge covers a huge area, about 26,609 acres. It has many different types of wetland and riverbank habitats. These habitats are home to a wide variety of birds, mammals, and other wildlife.
The San Joaquin Valley and Farming
The San Joaquin Valley is where Kesterson is located. It's known for being one of the most productive farming areas on Earth. About 25% of all farm products in the United States come from here. This includes grapes, cotton, nuts, and vegetables. The land here is very rich in nutrients. Long ago, it was an inland lake with many clams, and their shells made the soil rich.
The valley is surrounded by mountains. The Coast Range mountains to the west have rocks that naturally contain selenium. When these rocks break down, selenium can wash into the valley. The San Joaquin Valley also has a shallow layer of underground water. This water is trapped by clay, so it doesn't drain away easily.
Why Irrigation is Needed
The climate in the San Joaquin Valley is very dry. It gets only about 10 inches (250 mm) of rain each year. But it loses over 90 inches (2,300 mm) of water to evaporation. To grow crops, farmers need a lot of extra water. So, they use large irrigation systems to water their fields.
Over time, this irrigation caused the underground water levels to rise. Too much water started to harm the crops. In 1968, a plan was made to build a long drainage canal. It was called the San Luis Drain and was supposed to be 290 miles long. As part of this plan, the Kesterson Reservoir was finished in 1971. It had 12 ponds to collect the drainage water.
Kesterson Reservoir: A Timeline
Here are the important events in Kesterson's history:
- 1960s: The idea for the San Luis Drain, a long canal, was first suggested.
- 1971: The Kesterson Reservoir was built by the Bureau of Reclamation. It was part of the bigger drainage canal project.
- 1975: Only 82 miles of the canal were built before the project stopped. This was due to worries about the environment. Kesterson became the end point for the drainage system.
- 1978: A farming area called Westland's Water District started sending a lot of drainage water into Kesterson.
- 1983-1985: Scientists studied Kesterson to see how farm drainage water affected birds. Their findings were serious. The California State Water Resources Control Board ordered the reservoir to close.
- 1986: Scientists found birds at Kesterson with serious deformities.
- 1989-2014: Efforts were made to clean up the area and monitor it.
- 2014: Selenium levels became stable and much lower, making the area safer.
What Caused the Contamination?
In 1985, Kesterson Reservoir was ordered to close. This happened because studies in 1983 showed that 64% of bird embryos and young birds were deformed or died. This was due to selenium contamination. The selenium came from irrigation water that had flowed over rocks in the California Coast Ranges.
The U.S. Geological Survey (USGS) called this problem the "Kesterson effect." It described how selenium moved "from rock to duck." The health problems seen in birds at Kesterson are known as "Kesterson Syndrome."
Selenium: A Natural Element
Selenium is found naturally in the environment. It's actually important for our bodies in small amounts. But too much selenium can be very harmful. It can build up in living things, causing health problems like birth defects. It can also settle in the soil and water.
Because there's a lot of selenium in the Coast Range mountains, it washed into the San Joaquin Valley. Selenium became a big problem after drainage pipes were put in at Kesterson. From 1971 to 1978, the reservoir only received fresh water. But after 1978, all the water coming into Kesterson was salty drainage water. This water also contained a lot of selenium.
By 1983, selenium levels were very high. From 1981 to 1986, about 9,000 kg (nearly 20,000 pounds) of selenium entered Kesterson. As the drainage water evaporated from the ponds, the selenium became even more concentrated. This high level of selenium then built up in the birds and other wildlife using the reservoir.
Effects on Wildlife
Before 1981, Kesterson Reservoir was full of different kinds of life, including many fish. After 1981, only fish that could handle very salty water, like mosquito fish, could survive. In 1982, scientists started studying why wildlife was disappearing. They found extremely high selenium levels in the water. Mosquito fish from Kesterson had 70 times more selenium than fish from a clean area nearby.
In 1983, researchers looked at selenium in the diets and bodies of Kesterson's birds. They found that selenium was the main reason for the many birth defects in young fish and birds. These problems included missing or deformed eyes, beaks, wings, and legs. Adult birds at Kesterson had 10 times more selenium than birds from a control site. Bird eggs had 20-30 times more. Birds were also much lighter than normal.
The more time birds spent at Kesterson and the more they ate there, the higher their selenium levels were. Selenium also increased in plants, insects, and other animals. Birds are especially sensitive to high selenium levels. Kesterson was an important stop for migratory birds because many wetland habitats in California were disappearing. So, the high selenium levels had a huge impact on bird populations.
The study's findings were shared in newspapers and on TV. This brought national attention to the problem. It eventually led to the reservoir being closed in 1986.
Cleaning Up Kesterson
After the California State Water Resources Control Board ordered Kesterson to be cleaned up in 1985, the United States Bureau of Reclamation and the US Department of the Interior started working. They filled 713 acres of Kesterson with about 1 million cubic yards of soil. They also cut down tall plants called cattails. This was done to remove nesting places for birds, keeping them away from the contaminated areas.
These actions created three main types of land: grasslands, filled areas with annual plants, and open areas where cattails used to be. Even though the selenium problem only lasted a few years, the cleanup took more than 20 years. The total cost for the cleanup was about $21 million. Scientists also found that tiny microbes in the soil could help remove selenium.
Monitoring of selenium levels began in 1989 and became less frequent after 2012. By 2013-2014, selenium levels were stable and low enough to be safer for animals. However, experts know that big changes, like floods, could cause selenium to move around again. This could create new risks for wildlife.
Scientists are still looking for ways to handle contaminated irrigation water. Some ideas include special water treatments or new evaporation ponds.
