Question: Keith County, Nebraska is located over what 174000 sq mi aquifer?

full_context: Document 1: Keystone, Nebraska: Keystone is an unincorporated community and census-designated place in central Keith County, Nebraska, United States. It lies along local roads near the North Platte River, northeast of the city of Ogallala, the county seat of Keith County. Its elevation is 3,100 feet (945 m). Although Keystone is unincorporated, it has a post office, with the ZIP code of 69144.
Document 2: Ogallala Aquifer: The Ogallala Aquifer is a shallow water table aquifer surrounded by sand, silt, clay and gravel located beneath the Great Plains in the United States. One of the world's largest aquifers, it underlies an area of approximately 174000 sqmi in portions of eight states (South Dakota, Nebraska, Wyoming, Colorado, Kansas, Oklahoma, New Mexico, and Texas). It was named in 1898 by geologist N. H. Darton from its type locality near the town of Ogallala, Nebraska. The aquifer is part of the High Plains Aquifer System, and rests on the Ogallala Formation, which is the principal geologic unit underlying 80% of the High Plains.
Document 3: Alliance, Nebraska: Alliance is a city in Box Butte County, in the northwestern part of the state of Nebraska, in the Great Plains region of the United States. Its population was 8,491 at the 2010 census. It is the county seat of Box Butte County.
Document 4: Floridan aquifer: The Floridan aquifer system, composed of the Upper and Lower Floridan aquifers, is a thick sequence of Paleogene carbonate rock which spans an area of about in the southeastern United States. It underlies the entire state of Florida and parts of Alabama, Georgia, Mississippi, and South Carolina.
Document 5: Box Butte County, Nebraska: Box Butte County is a county in the U.S. state of Nebraska. As of the 2010 census, the population was 11,308. Its county seat is Alliance. The county was formed in 1886. Box Butte is the name of a geological formation in the county's eastern part.
Document 6: Nebraska: Nebraska is a state that lies in both the Great Plains and the Midwestern United States. The state is bordered by South Dakota to the north, Iowa to the east and Missouri to the southeast, both across the Missouri River, Kansas to the south, Colorado to the southwest and Wyoming to the west. It is the only triply landlocked U.S. state. Nebraska's area is just over 77,220 sq mi (200,000 km) with almost 1.9 million people. Its state capital is Lincoln, and its largest city is Omaha, which is on the Missouri River.
Document 7: Osage Plains: The Osage Plains are a physiographic section of the larger Central Lowland province, which in turn is part of the larger Interior Plains physiographic division. The area is sometimes called the Lower Plains, North Central Plains, and the Rolling Plains. The Osage Plains, covering west-central Missouri, the southeastern third of Kansas, most of central Oklahoma, and extending into north-central Texas, is the southernmost of three tallgrass prairie physiographic areas. It grades into savanna and woodland to the east and south, and into shorter mixed-grass prairie to the west. The Osage Plains consist of three subregions. The Osage Plains proper occupy the northeast segment. Although sharply demarcated from the Ozark uplift, the Plains are nonetheless a transitional area across which the boundary between prairie and woodland has shifted over time. In the central portion of the physiographic area lies the second subregion, the Flint Hills, commonly called "The Osage" in Oklahoma. This large remnant core of native tallgrass prairie is a rocky rolling terrain that run from north to south across Kansas and extends into Oklahoma. To the west and south of these hills are the Blackland Prairies and Cross Timbers. This vegetatively complex region of intermixed prairie and scrubby juniper-mesquite woodland extends into north-central Texas. Bluestem prairies and oak-dominated savannas and woodlands characterize the natural vegetation in the Cross Timbers. Much of the area has been converted to agriculture, although expanses of oak forest and woodland are still scattered throughout the eastern portion of the subregion.
Document 8: Loup City, Nebraska: Loup City is the county seat of Sherman County, in the central portion of the Midwestern state of Nebraska, United States. The population was 1,029 at the 2010 census. Loup City is close to the Middle Loup River, and about five miles from Sherman Reservoir.
Document 9: Snake River Aquifer: The Snake River Aquifer is a large reservoir of groundwater underlying the Snake River Plain in the southern part of the U.S. state of Idaho. Most of the water in the aquifer comes from rain and melting snow that flows onto the plain from the Snake River, Big Lost River, Bruneau River, and other watercourses of southern Idaho. Measuring about 400 mi from east to west, it is an important water source for agricultural irrigation in the Plain. The Snake River Aquifer is commonly defined as two separate parts, separated by Salmon Falls Creek. These are the Eastern Snake River Plain Aquifer and Western Snake River Plain Aquifer.
Document 10: Ogallala, Nebraska: Ogallala is a city in Keith County, Nebraska, United States. The population was 4,737 at the 2010 census. It is the county seat of Keith County. In the days of the Nebraska Territory, the city was a stop on the Pony Express and later along the transcontinental railroad. The Ogallala Aquifer was named after the city.
Document 11: Wagon Bed Spring (Kansas): Wagon Bed Spring (also Lower Spring or Lower Cimarron Spring), located in Grant County, Kansas, United States, was an important watering spot on the Cimarron Cutoff of the Santa Fe Trail. The flow of the spring came from an outcropping of the Ogallala Formation. Center pivot irrigation adjacent to the spring resulted in lowering of the water table and the spring ceased to flow in the 1960s. A number of small artifacts dating from the days of the Santa Fe Trail have been recovered from lands near the spring which were used by both American Indians and wagon trains as a campground. The name "wagon bed" dates from later use of an old wagon bed as a trough to collect water from the spring. There is a foundation on the site of an ice house. Floods have changed the course of the Cimarron River; the site of the spring is now in the bed of the river rather than on its bank as it was in the days of the Santa Fe Trail.
Document 12: Lincoln County, Nebraska: Lincoln County is a county located in the U.S. state of Nebraska. As of the 2010 census, the population was 36,288. Its county seat is North Platte. Despite the county's name, the state capital city of Lincoln is not located in or near Lincoln County.
Document 13: High Plains (United States): The High Plains are a subregion of the Great Plains mostly in the Western United States, but also partly in the Midwest states of Nebraska, Kansas, and South Dakota, generally encompassing the western part of the Great Plains before the region reaches the Rocky Mountains. The High Plains are located in southeastern Wyoming, southwestern South Dakota, western Nebraska, eastern Colorado, western Kansas, eastern New Mexico, western Oklahoma, and south of the Texas Panhandle. The southern region of the Western High Plains ecology region contains the geological formation known as Llano Estacado which can be seen from a short distance or from on satellite maps. From east to west, the High Plains rise in elevation from around 1160 ft to over 7800 ft .
Document 14: Great Plains: The Great Plains (sometimes simply "the Plains") is the broad expanse of flat land (a plain), much of it covered in prairie, steppe and grassland, that lies west of the Mississippi River tallgrass prairie states and east of the Rocky Mountains in the United States and Canada. It embraces
Document 15: Lemoyne, Nebraska: Lemoyne is an unincorporated community and census-designated place in northern Keith County, Nebraska, United States. It lies along Nebraska Highway 92 on the northern shore of Lake C.W. McConaughy, north of the city of Ogallala, the county seat of Keith County. Its elevation is 3,333 feet (1,016 m). Although Lemoyne is unincorporated, it has a post office, with the ZIP code of 69146.
ground_truth: Ogallala Aquifer