II.

Physical Geography

Nebraska ranks 16th among the states in area, covering 200,346 sq km (77,354 sq mi), including 1,246 sq km (481 sq mi) of inland waters. From east to west, in a line extending from Omaha to the western boundary of its Panhandle, Nebraska measures 687 km (426 mi). The distance from north to south is 333 km (207 mi).

With the exception of the Panhandle to the west, the state is rectangular. It slopes gently to the southeast and elevation increases at an average rate of 2 meters per kilometer (10 feet per mile) from the Missouri River to Nebraska’s western boundary. The lowest elevation, 256 m (840 ft), is along the Missouri River in the southeast, and the highest point, 1,653 m (5,424 ft), is in the Panhandle in southwestern Kimball County. The mean elevation is about 790 m (2,600 ft). Although Nebraska is considered a plains state, there is considerable local relief.

A.

Natural Regions

Two major physiographic divisions, or natural regions, of the United States are represented in Nebraska. They are the Central Lowland and the Great Plains, both of which are subdivisions of the Interior Plains. The eastern fifth of Nebraska is in the Central Lowland, and the remainder of the state forms part of the Great Plains. The Dissected Till Plains of the Central Lowland, which average about 110 to 130 km (about 70 to 80 mi) in width, parallel the Missouri River. This area was blanketed by ice during the early ice ages several hundred thousand years ago. Later it was covered by various thicknesses of loess, or wind-deposited material, and roughened by erosion. The hills of loess-covered glacial deposits are severely dissected, or eroded, by rivers enlarging their valleys near the Missouri River. This dissection has created bluffs that are visible along much of the river.

The Great Plains natural region covers about four-fifths of the state. This region is composed of four distinct areas: the High Plains, the Sand Hills, the Loess Hills and Canyons, and the Loess Plains.

The High Plains in western Nebraska consist of a large expanse of high flat tableland with some rough broken areas. In many areas the soil and mantle are thin and the bedrock is exposed. A rather prominent feature of the landscape in this region is the Pine Ridge Escarpment, a cliff of 300 m (1,000 ft) in elevation. The Sand Hills in central and north central Nebraska consist of grass-covered sand dunes. This region makes up about one-quarter of the state. The sand dunes have been completely grassed over, except for occasional blowouts, which are areas of exposed sand that may cover more than a hectare. Throughout the region there is little variation in composition or in texture of the soil. The Sand Hills are extremely porous, and there is little surface runoff. Most streams in the Sand Hills are fed by springs or artesian wells and have little seasonal fluctuation. The underlying rock strata hold large amounts of usable water, and wells may be dug successfully anywhere within the Sand Hills.

The central and southwestern parts of the Great Plains in Nebraska are made up of loess hills and canyons. Most of south central Nebraska is composed of a slightly dissected loess plain. Most of the southeastern half of the state is capped by loess, ranging in depth from about 1 to more than 90 m (about 3 to more than 300 ft). The thickest deposits are found in central Nebraska, from 60 to 160 km (40 to 100 mi) north of the Kansas border. The loess is windblown unstratified material that often stands nearly vertical in cliffs or road cuts. Soils develop rapidly on loess and are among the most productive in the world.

B.

Rivers, Lakes, and Irrigation

Nebraska has one of the best supplies of surface and underground water in the nation. All of its rivers and streams eventually drain into the Missouri River, flowing in an easterly and southeasterly direction. The state’s principal river, the Platte, is formed by the confluence of the North Platte and South Platte rivers, both of which rise in the Rocky Mountains. The Platte River flows through central Nebraska to the Missouri River. The Sand Hills are drained by the Niobrara, Elkhorn, and Loup rivers. The Republican and Big Blue rivers drain the southern part of the state, flowing south into Kansas, where they enter the Kansas River. While there are no large natural lakes in the state, hundreds of small natural lakes are found in the Sand Hills.

Nebraska depends on irrigation for a substantial part of its crop production, and 26 percent of all cropland is irrigated. Much of the irrigated land is in the broad valley of the Platte. Because of the abundant surface and underground water supplies, the valley has been given the nickname “Irrigation Way.”

One of the first United States Bureau of Reclamation projects, the North Platte Project, was built in Nebraska and Wyoming. Water impounded and stored in Wyoming is used for irrigation in southeastern Wyoming and Scotts Bluff and Morrill counties in Nebraska.

A large privately financed irrigation project, the Tri-County Project, uses Platte River water. The state’s largest dam, Kingsley Dam, and largest reservoir, Lake McConaughy, are parts of the Tri-County Project. Three other reservoirs, Lewis and Clark Lake, Harlan County Lake, and Swanson Lake, each have an immense storage capacity. Other major reservoirs in Nebraska include Harry Strunk Lake, Hugh Butler Lake, Enders Reservoir, and Sherman Reservoir.

Nearly four-fifths of the irrigated land in Nebraska, however, uses groundwater pumped from deep wells, rather than surface water supplied from reservoirs. Nebraska possesses enormous groundwater reserves. The Ogallala aquifer, an underground-water bearing layer stretching south as far as Texas, lies under much of central Nebraska. Well irrigation first became important in the late 1930s, but the number of wells increased sharply in the 1950s and 1970s. In the mid-1990s there were more than 60,000 irrigation wells in the state, with the greatest concentrations found in the central and lower Platte valleys, in south central and southwestern Nebraska, and in much of the north central part of the state. The growth in irrigation has put pressure on groundwater supplies and has led to declining water tables in some areas, particularly in the Big Blue River basin and in the southwestern counties. When water tables decline quite rapidly, various restrictions may be put into place by natural resource districts to limit the rate of pumping for irrigation.

C.

Climate

Nebraska has a typical continental climate with wide seasonal variations in temperature.

C.1.

Temperature

Winter temperatures below -20°C (0° F) and summer temperatures in the upper 30°s C (lower 100°s F) are common.

The average January temperature varies from about -7° C (about 20° F) in the northeast to about -2° C (about 29° F) in the southwest. The average for July, the hottest month, ranges from about 26° C (about 78° F) in the south central section to about 20° C (about 68° F) along the western tip of Nebraska.

C.2.

Precipitation

Nebraska is fortunate in that approximately three-fourths of its precipitation falls during the April through September growing season. Normally, May and June are the wettest months and December and January are the driest. Average snowfall normally ranges from about 500 to 1,000 mm (about 20 to 40 in) with the heaviest snows in late winter. Blizzards are common. The blizzard in 1888 claimed thousands of livestock and many lives, and the blizzard in 1949 required the aid of United States armed forces. Precipitation in the northwest averages about 360 mm (about 14 in) annually, increasing to more than 860 mm (34 in) in the southeast. Along the 100th meridian, which bisects the state, annual precipitation averages about 500 mm (about 20 in).

Severe storms, with damaging winds, hail, and torrential rains of 100 mm (4 in) or more, are common. Tornadoes occur every year, but their number and intensity vary. Hailstorms are very severe in western Nebraska, which probably has the highest hail frequency in the country. During dry years, dust storms occasionally develop in the Panhandle and in the southwestern part of Nebraska.

C.3.

The Growing Season

The growing season ranges from 130 days in the west to more than 170 days in the east. The last killing frost is usually in late April or early May, and the first killing frost generally occurs in late September or early October.

D.

Soils

Light precipitation, rich parent material, and grasses have been the major ingredients in providing Nebraska with some of the most fertile and productive soils in the world. The rich parent material, particularly the soil-like loess, has accelerated soil formation. The grass cover has increased fertility by providing large amounts of humus in the topsoil. Light precipitation has limited leaching, or the washing away of valuable organic matter. The high degree of productivity of the land is a major reason why nearly 95 percent of the land area of the state is in agricultural use.

The soils of Nebraska can be divided into five major groups: the prairie soils in the southeast, chernozem in the central and northeastern areas, chestnut in the west, the Sand Hills soils in north central Nebraska, and rich alluvial soils along the floodplains of the major rivers. With the exception of the Sand Hills soils, all the soils are intensively cultivated.

E.

Plant Life

Originally, grasslands covered about 98 percent of the state and forests only 2 percent. Bluestem and switch grass were the major grasses in the east. Blue grama, side oats grama, and a shorter variety of bluestem were common in central Nebraska, with shorter gramas and buffalo grasses prevailing in the west. Bluestem and sand dropseed were found principally in the Sand Hills. Cultivation and grazing have to a large extent changed their composition and stands. Many invaders, such as thistle, cactus, and yucca, can be found in the grasslands of the Sand Hills where grazing has outrun the growing capacity of the grasses. In central and eastern Nebraska overgrazed pastures are experiencing an increase in cool-season grasses, such as bluegrass and bromegrass, to the detriment of the native grasses. Serious invasions of noxious weeds such as leafy spurge and spotted knapweed are occurring across the state.

Currently forests cover just 2 percent of Nebraska’s land area. Trees are found along the river valleys and on some of the higher tablelands in the west. These are primarily deciduous trees. The cottonwood, elm, ash, maple, oak, and willow are the most common species. On the rougher and higher lands in the west large stands of coniferous trees are found. The predominant species are ponderosa pines and redcedars. Since the late 1800s the Eastern redcedar has been expanding throughout the state. Along the bluffs of the Missouri River and in the eastern third of Nebraska oak, black walnut, and hickories are occasionally found.

F.

Animal Life

Bison (American buffalo), mule deer, white-tailed deer, pronghorn, coyote, beaver, prairie dog, jackrabbit, skunk, and squirrel were found in large numbers by the first settlers. Bison, in particular, were hunted indiscriminately and were eliminated by the 1880s. Other species have survived and prospered. Pheasant, quail, sharp-tailed grouse, prairie chicken, and wild turkey are also abundant. Wildlife has increased considerably in recent years as conservation practices have been applied to the land and as farmland has been converted to grassland. Many migratory waterfowl, varieties of shorebirds, and the nearly extinct whooping crane use Nebraska waters during the fall and spring migrations. Thousands of sandhill cranes stop along the central Platte River every year during their migration. Crappie, perch, pike, catfish, bullhead, bass, bluegill, and trout abound in Nebraska’s lakes and streams. Fish hatcheries may be found near Benkelman, North Platte, Valentine, and Burwell.

G.

Conservation

Nebraska has implemented numerous programs to protect its natural resources, especially soil and water. Contour farming, whereby crops are planted to follow the contour of hills; strip-cropping, or alternating close-growing forage crops that retain and rebuild the soil with cash crops; and grazing controls are commonly used to prevent soil erosion. During the 1930s many shelterbelts were planted across the state to reduce wind erosion and protect crops. Many watershed projects have been developed to minimize flooding, especially in southeastern Nebraska. The largest project is the Salt-Wahoo, which provides protection for Lincoln and for other parts of Lancaster County. Upstream dams in the Dakotas and Montana have reduced large-scale flooding along the Missouri River. Flooding on the Republican River is largely controlled by five reservoirs in Nebraska, as well as by others in Colorado and Kansas.

The use of underground water is regulated through a system of natural resources districts. The 23 natural resources districts conduct water quality planning programs. The Department of Environmental Quality, established in 1971, is responsible for air and water pollution control, solid and hazardous waste management. Laws concerning drinking water standards and radiation control are administered by the Department of Health.

In 2006 Nebraska had 12 hazardous waste sites on a national priority list for cleanup due to their severity or proximity to people. Between 1995 and 2000, the amount of toxic chemicals discharged into the environment increased by 52 percent.