The 10 Largest Man-Made Lakes in the United States

Key Points

• Manmade lakes are created by means like excavation or interrupting a water source to trap water and form an embayment.
• There are more than 53,000 manmade lakes in the US, close to equaling the percentage of its natural lakes.
• Lake Mead is the largest manmade lake in the United States, and one of the largest in the world.
• Besides being the second largest manmade lake in the US, Lake Powell attracts countless tourists for its breathtaking scenery.

A man-made lake, more commonly called a reservoir, is an artificial lake built along or adjacent to dams to supply water for several purposes. Man-made lakes store fresh water and can be created through many ways, such as excavation and interrupting a water source to trap water and form an embayment. There are plenty of reservoirs spread throughout the globe, and in the United States alone, more than 53,000 lakes are man-made, taking up 48% of all the country’s lakes or almost the same number of natural lakes in the U.S. According to the National Lakes Assessment (NLA), the natural lakes in the country are distributed among an even range of small to large sizes by surface area and volume. In contrast, the man-made lakes are significantly smaller. The report also stated that 40% of the man-made lakes are less than 10 acres in surface area. Despite this, some reservoirs are still vast enough to seem like a natural lake.

Reservoirs can serve many purposes, such as providing hydroelectric power, drinking water, irrigation for agriculture, flood control, fisheries, recreation, or navigation from one place to another. They can also create habitats for a vast array of animals. Many of the largest ones in the US serve multiple purposes at one time.

So, what are these massive man-made lakes, and where can we find them? Below, we will explore the 10 largest man-made lakes in the United States.

The 10 Largest Man-Made Lakes in the United States

1. Lake Mead, Nevada

With a total capacity of 28,945,000 acre-feet and stretching 112 miles long, Lake Mead tops as the largest man-made lake in the United States. With a deepest point that measures 532 feet and a shoreline that extends up to 759 miles, it also ranks as one of the biggest man-made lakes in the world. Lake Mead is located at the Arizona–Nevada border and was formed by the damming of the world-famous Hoover Dam in the Colorado River. Established in 1936, the reservoir was built to provide hydroelectric power, water supply, recreational activities, and a habitat for diverse wildlife. Although Lake Mead is the largest dam in the U.S. based on capacity, it doesn’t usually fill up due to the prolonged drought in Arizona, Nevada, and California. As Lake Mead supplies water to over 20 million people living around these states, the last time it filled its capacity was in 1983. Often, Lake Mead sits at around 40% of its capacity.

2. Lake Powell, Arizona

Lake Powell has a total capacity of 26,214,900 acre-feet and a total surface area of 161,000 acres, making it the second-largest reservoir in the United States. Apart from providing massive water storage for the American states of Colorado, Utah, Wyoming, and New Mexico, Lake Powell is also well-known for its breathtaking scenery, attracting about two million tourists and visitors every year. Like Lake Mead, Lake Powell was also created by a dam (Glen Canyon Dam) on the Colorado River. It has a maximum depth of 532 feet and is located where the states of Arizona and Utah meet. The water that feeds the reservoir comes from melted snow during the spring months. 

3. Lake Sakakawea, North Dakota

Covering a total surface area of 307,000 acres, Lake Sakakawea in North Dakota has a full capacity of 24,300,000 acre-feet. The lake has a maximum depth of 180 feet and has a shoreline that extends up to 1,320 miles, making it the largest man-made lake in the state of North Dakota and the third-largest in the country. The reservoir was built by the Garrison Dam to host recreational activities such as boating, fishing, and others. Apart from this function, the dam was also created to provide irrigation, navigation, flood control, and hydroelectric power. Damming the Missouri River, Lake Sakakawea was finished in 1953 and took three to ten years to fill its capacity.

4. Lake Oahe, South Dakota

Lake Oahe ranks as the fourth largest man-made lake in the United States, with a total capacity of 23,500,000 acre-feet. It covers a total surface area of 374,000 acres and extends for 231 miles across South Dakota. The reservoir was built to serve as flood control and provide hydroelectric power, irrigation, recreation, navigation benefits, and habitat for diverse wildlife. It was created by the Oahe Dam, which is 245 feet tall and 9,360 feet long and is the fifth largest dam on the planet based on water volume. Lake Oahe may be man-made, but it hosts a rich ecosystem that includes many freshwater fish like walleye, pike, catfish, bass, and salmon. Nearly 1.5 million people visit the reservoir annually.

5. Fort Peck Lake, Montana

With a total capacity of 19,100,000 acre-feet, Fort Peck Lake ranks as the fifth-largest man-made lake in the United States. Fort Peck is a primary reservoir in Montana, built by the Fort Peck Dam in the Missouri River. It has an extensive shoreline that measures 1,520 miles in length, even longer than the coastline of California. Fort Peck Lake covers an entire surface area of 245,000 acres, and its deepest point measures 220 feet down. Fort Peck Lake was built primarily for flood control, water quality management, and hydroelectric power. Lying inside the Charles M. Russell National Wildlife Refuge, the reservoir also hosts many fish species.

6. Lake Franklin, Washington

More commonly called the Franklin D. Roosevelt Reservoir, Lake Franklin boasts a total capacity of 9,562,000 acre-feet, making it the sixth-largest man-made lake in the United States. Its wowing volume and surface area make it the largest Washington reservoir, covering 125 square miles. Lake Franklin also has a shoreline that extends over 600 miles and a maximum depth of 46 feet. Its main functions include hydroelectric power, water supply, recreation, and wildlife habitat. Plenty of freshwater fish species can be found in the reservoir, such as the northern pike, largemouth bass, smallmouth bass, walleye, and panfish. The lake was impounded by the Grand Coulee Dam on the Columbia River, constructed between 1933 and 1941.

7. Lake Cumberland, Kentucky

With a total capacity of 6,089,000 acre-feet, Lake Cumberland lands seventh place in the largest man-made lakes in the United States. It also boasts a shoreline that extends 1,225 miles across different counties in Kentucky, namely, Wayne, Russell, Clinton, Pulaski, Laurel, and McCreary. The reservoir covers 65,530 acres or 265 square kilometers of surface area and contains 7.5 cubic kilometers of water, enough to inundate the whole Commonwealth of Kentucky with 3 inches or 76 mm of water. Lake Cumberland was originally constructed for flood control and hydroelectric power production. Over the years, the reservoir has been a primary source of tourism and has become an economic engine for the area. It was formed by the Wolf Creek Dam on the Cumberland River. 

8. Lake Koocanusa, Montana

Ranking as the eighth largest man-made lake in the United States, Lake Koocanusa boasts a total capacity of 5,869,200 acre-feet and has a maximum depth of 310 feet. Canada and the United States share the reservoir through British Columbia and Montana. It stretches 90 miles across the northern region of Montana and was formed by the Libby Dam on the Kootenai River in 1972. Lake Koocanusa contains 13% of the Columbia River system’s waters and serves primarily as a water supply to Canada and the U.S. The reservoir also provides flood protection, hydroelectric power, and habitat for wildlife. The bizarre name “Koocanusa” was formed from the first syllables of Kootenai River, Canada, and the USA (KooCanUSA). The lake is also home to the most common freshwater fish species such as burbot, sockeye salmon, and rainbow trout. 

9. Shasta Lake, California

Also known as Lake Shasta, the Shasta Lake ranks among the largest man-made lakes in the United States. It has a total water capacity of 4,552,000 acre-feet with a maximum depth of 517 feet and a mountainous shoreline extending to 365 miles. Located in Shasta County, California, Shasta Lake is the largest reservoir entirely within the state of California. Lake Shasta was impounded by the Shasta Dam across the Sacramento River, with the primary function of providing flood control, hydroelectric power, water storage, and protection against saltwater. The reservoir’s crystal blue waters are ideal for recreational activities such as boating, fishing, skiing, and more.

10. Toledo Bend Lake, Louisiana and Texas

Covering a total surface area of about 181,600 acres and having a total water capacity of 4,472,900 acre-feet, the Toledo Bend Lake is one of the country’s largest man-made lakes and the biggest in Texas. With a maximum depth of 34 meters, the lake also contains the largest water volume among all lakes in the state. This reservoir is shared by two states –Texas and Louisiana. The construction of the Toledo Bend Dam started in 1964 and was completed in 1969 on the Sabine River. The project’s primary purpose is for the generation of hydroelectric power, water supply, and recreation. With a surface area of 73,500 hectares, the Toledo Bend Lake can generate up to 92 megawatts of electrical power.

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