The Rainwater Basin wetland region is a

loess Loess (, ; from german: Löss ) is a clastic, predominantly silt-sized sediment that is formed by the accumulation of wind-blown dust. Ten percent of Earth's land area is covered by loess or similar deposits. Loess is a periglacial or aeolian ...

plain located south of the Platte River in south-central

Nebraska Nebraska () is a state in the Midwestern region of the United States. It 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 southwe ...

.Krueger, J.P., 1986. ''Development of oriented lakes in the eastern rainbasin region of south-central Nebraska.'' Master’s thesis, Department of Geology. University of Nebraska-Lincoln, Lincoln, NE. It lies principally in Adams, Butler, Clay, Fillmore, Hamilton, Kearney, Phelps, Polk, Saline, Seward, and York counties and extends into adjacent areas of southeastern Hall, northern Franklin, northern Nuckolls, western Saline, northern Thayer and northwestern Webster counties. Before European settlement, this plain was covered by prairie

grassland A grassland is an area where the vegetation is dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur natur ...

s interspersed with thousands of ephemeral playa

wetland A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The ...

s, called Rainwater Basins. Informally and locally, individual Nebraska Rainwater Basins are referred to as ''rainbasins'', ''basins'', ''lagoons'', ''lakes'', ''ponds'', ''marshes'', ''hay marshes'', and ''lakes marshes''. To the west, a tallgrass prairie in the east once gradually transitioned into

mixed grass prairie A mixed-grass prairie is an ecotone located between the tallgrass prairies and shortgrass prairies. The mixed-grass prairie is richer in ecological diversity than either the tall- or shortgrass prairie. The mixed-grass prairie occurs in the ce ...

. Currently, the Rainwater Basin wetland region is covered by farms, mainly growing

corn Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. Th ...

and

soybean The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean, which has numerous uses. Traditional unfermented food uses of soybeans include soy milk, from which tofu an ...

s. Several, interspersed,

stream A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a stream ...

courses, of which largest is the Big Blue River and its tributaries, drain this region. Riparian woodlands and upland slopes possessing oak woodlands are associated with these streams.Kaul, R.B., and Rolfsmeier, S.B., 1983. ''Native vegetation of Nebraska'' (Map). Lincoln: Conservation and Survey Division, University of Nebraska-Lincoln.Jorgensen, J.G., 2004
''An overview of shorebird migration in the Eastern Rainwater Basin, Nebraska.''
''Nebraska Ornithologists’ Union Occasional Paper'' No. 8. 53 pp. In the spring and fall months, millions of

migratory birds Bird migration is the regular seasonal movement, often north and south along a flyway, between breeding and wintering grounds. Many species of bird migrate. Migration carries high costs in predation and mortality, including from hunting by ...

pass through the region to feed and rest. Along with riparian habitats associated Platte River, Big Blue River, its tributaries, and smaller streams, Rainwater Basins are a major component of the Central Flyway of

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

.Jorgensen, J.G., 2012
Birds of the Rainwater Basin, Nebraska
Lincoln: Nebraska Game and Parks Commission. 121 pp. Prior to its agricultural development in historic times, the Rainwater Basin wetland region was characterized by numerous playa wetlands, ''Rainwater Basins'', numbering in the thousands. The shallow depressions, in which these wetlands occur are lined with a nearly impervious layer of clayey soil, a claypan, that prohibits surface water from penetrating the subsoil. As a result, Rainwater Basins are not naturally influenced by the water table and the sole source of water is run-off in the form of rain, snow and, currently, drainage from crop

irrigation Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow Crop, crops, Landscape plant, landscape plants, and Lawn, lawns. Irrigation has been a key aspect of agriculture for over 5,00 ...

. Because the primary source of water for these wetlands is

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...

, they annually vary in depth, expanse and seasonality due to changes in precipitation regimes and are called ''Rainwater Basins''.LaGrange, T., 1997. ''Guide to Nebraska’s wetlands and their conservation needs''. Lincoln: Nebraska Game and Parks Commission.

Rainwater Basin Wetland Management District

The Rainwater Basin Wetland Management District consists of 61 tracts of land, 59 of which are Waterfowl Production Areas, totaling managed by the U.S. Fish and Wildlife Service. Established in 1963, the district is a complex of wetlands scattered across a 21-county area of Nebraska. One of the remaining two areas is McMurtrey Wildlife Management Area that was transferred from the

U.S. Military The United States Armed Forces are the military forces of the United States. The armed forces consists of six service branches: the Army, Marine Corps, Navy, Air Force, Space Force, and Coast Guard. The president of the United States is the ...

and is closed to public use. The other tract is the Platte River National Wildlife Management Area and this property is owned by the state of

Wyoming Wyoming () is a U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the south ...

and managed through a memorandum of understanding. WPAs are small isolated tracts of land scattered throughout the District. The Wetland Management District is managed from offices in

Kearney, Nebraska Kearney is the county seat of Buffalo County, Nebraska, United States. The population was 30,787 in the 2010 census. It is home to the University of Nebraska at Kearney. The westward push of the railroad as the Civil War ended gave new birt ...

. All of the federally managed land was acquired from willing landowners and purchased with the proceeds of duck stamps that are sold to hunters each year.

Birds of the Rainwater Basin

The Rainwater Basin wetland region is a prime location for birdwatching; 257 bird species have been observed in the region.''Rainwater Basin Facts''.
Lincoln: Nebraska Game and Parks Commission Species in the Rainwater Basin include: *

Bald eagle The bald eagle (''Haliaeetus leucocephalus'') is a bird of prey found in North America. A sea eagle, it has two known subspecies and forms a species pair with the white-tailed eagle (''Haliaeetus albicilla''), which occupies the same niche as ...

Canada goose The Canada goose (''Branta canadensis''), or Canadian goose, is a large wild goose with a black head and neck, white cheeks, white under its chin, and a brown body. It is native to the arctic and temperate regions of North America, and it is o ...

* Killdeer *

Least sandpiper The least sandpiper (''Calidris minutilla'') is the smallest shorebird. The genus name is from Ancient Greek ''kalidris'' or ''skalidris'', a term used by Aristotle for some grey-colored waterside birds. The specific ''minutilla'' is Medieval Lat ...

Mallard The mallard () or wild duck (''Anas platyrhynchos'') is a dabbling duck that breeds throughout the temperate and subtropical Americas, Eurasia, and North Africa, and has been introduced to New Zealand, Australia, Peru, Brazil, Uruguay, Arge ...

Northern pintail The pintail or northern pintail (''Anas acuta'') is a duck species with wide geographic distribution that breeds in the northern areas of Europe and across the Palearctic and North America. It is migratory and winters south of its breeding ra ...

Northern shoveler The northern shoveler (; ''Spatula clypeata''), known simply in Britain as the shoveler, is a common and widespread duck. It breeds in northern areas of Europe and across the Palearctic and across most of North America, wintering in southern Euro ...

Peregrine falcon The peregrine falcon (''Falco peregrinus''), also known as the peregrine, and historically as the duck hawk in North America, is a Cosmopolitan distribution, cosmopolitan bird of prey (Bird of prey, raptor) in the family (biology), family Falco ...

Piping plover The piping plover (''Charadrius melodus'') is a small sand-colored, sparrow-sized shorebird that nests and feeds along coastal sand and gravel beaches in North America. The adult has yellow-orange-red legs, a black band across the forehead from e ...

* Sandhill crane * Snow goose *

White-fronted goose The greater white-fronted goose (''Anser albifrons'') is a species of goose related to the smaller lesser white-fronted goose (''A. erythropus''). It is named for the patch of white feathers bordering the base of its bill, in fact ''albifrons ...

* Greater and

lesser yellowlegs The lesser yellowlegs (''Tringa flavipes'') is a medium-sized shorebird. It breeds in the boreal forest region of North America. Taxonomy The lesser yellowlegs was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in ...

Rainwater Basins

The subtle depressions known locally as ''Rainwater Basins'' lie scattered across the loess plain of south-central Nebraska. The majority of them lie to the south of the Platte River. Prior to European settlement, there were nearly 4,000 of these wetlands totaling up . The smaller, ''pothole'' depressions, which are irregular in shape and do not exhibit any orientation, range from about in size. Their bottoms generally lie less than below the surrounding land surface at their lowest point. Most of these smaller depressions have been destroyed by agricultural activities such as filling, land leveling, drainage, and sedimentation.Kuzila, M.S., 1994
''Inherited morphologies of two large basins in Clay County, Nebraska.''
''Great Plains Research'', pp.51-63.Stutheit, R.G., Gilbert, M.C., Whited, P.W. and Lawrence, K.L., 2004
''A regional guidebook for applying the hydrogeomorphic approach to assessing wetland functions of rainwater basin depressional wetlands in Nebraska (No. ERDC/EL-TR-04-4)''.
U.S. Army Corps of Engineers, Washington, D.C. StarksStarks, P.J. 1984. ''Analysis of the rainbasin depressions of Clay County, Nebraska.'' Master’s thesis, Department of Geography and Geology. University of Nebraska-Omaha, NE. first recognized that the larger of these basins are approximately elliptical to elongate in shape. The larger and semi-elliptical of these basins typically measure about by . Most basins are closed depressions that hold runoff from the surrounding landscape to form seasonal lakes and wetlands in them. Some of these basins have been naturally ''breached'', or drain to an outside watershed, and no longer hold precipitation run-off. Many of the large semi-elliptical to elliptical Rainwater Basins have a crescent-shaped ridge that Stark referred to as a ''lunette'' located on the southeast side of them. These distinctive ridges are about in relief.Kuzila, M.S., 1988. ''Genesis and morphology of soils in and around large depressions in Clay County, Nebraska.'' PhD. Dissertation., Department of Agronomy. University of Nebraska-Lincoln, Lincoln, NE.Young, A.R., Hanson, P.R., Larsen, A.K., and Howard, L.M., 2018. ''Surficial Geology of the Edgar NW 7.5 Minute Quadrangle: Version 1.0.'' Conservation and Survey Division (Nebraska Geological Survey), School of Natural Resources, University of Nebraska-Lincoln. scale 1:24,000, supplement. Since European settlement of this region, about 90% of these wetlands have disappeared. Many have been drained so that the land could be used for

agricultural Agriculture or farming is the practice of cultivating Plant, plants and livestock. Agriculture was the key development in the rise of Sedentism, sedentary human civilization, whereby farming of Domestication, domesticated species created food ...

purposes. Many of the remaining sites have been set aside by government agencies and non-profit organizations; today, there are 84 publicly owned Rainwater Basin sites, totaling of protected wildlife habitat.

Geomorphology of Rainwater Basins

The large semi-elliptical to elliptical Rainwater Basins are the surface expression of older elliptical depressions developed in

fluvial In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluviog ...

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class of s ...

s and

gravel Gravel is a loose aggregation of rock fragments. Gravel occurs naturally throughout the world as a result of sedimentary and erosive geologic processes; it is also produced in large quantities commercially as crushed stone. Gravel is classifi ...

s that are buried by a blanket of a thick sequence of layered

es and associated paleosols. The loess, which overlies these features, consists of an undisturbed sequence, from bottom to top, of Middle

Wisconsinan The Wisconsin Glacial Episode, also called the Wisconsin glaciation, was the most recent glacial period of the North American ice sheet complex. This advance included the Cordilleran Ice Sheet, which nucleated in the northern North American Cor ...

Gilman Canyon Formation (loess), a regional paleosol developed in Gilman Canyon Formation, Late Wisconsinan Peoria Loess, Brady Soil (paleosol) developed in the Peoria Loess, and

Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...

Bignell Loess in which the modern soil has developed. This loess sequence lies upon a paleosol developed in the

s and

s in which these depressions initially developed. Thus, the modern basin landscape is a direct result of the accumulation a few meters of loess that blankets an older basin landscape. These basins are palimpsest landforms created by the episodic accumulation of a blanket of loess over a prehistoric landscape with numerous basins.Dillon, J.S., Hanson, P.R., Larsen, , A.K., Raymond, C., and Howard, L.M., 2016. ''Surficial Geology of the Kearney SW 7.5 Minute Quadrangle, Nebraska: Version 1.0.'' Conservation and Survey Division (Nebraska Geological Survey), School of Natural Resources, University of Nebraska-Lincoln. scale 1:24,000, supplement.Hanson, P.R., Young, A.R., Larsen, A.K., Howard, L.M. and Dillon, J.S., 2017. ''Surficial Geology of the Fairmont 7.5 Minute Quadrangle, Nebraska. Version 1.0'' Conservation and Survey Division (Nebraska Geological Survey), School of Natural Resources, University of Nebraska-Lincoln. scale 1:24,000, supplement. Like their associated Rainwater Basins, the crescent-shaped ridges (lunettes) are also blanketed by loess. Although a complete sequence of Peoria loess overlying Gilman Canyon Formation and associated paleosols cover the ridges, the overall thickness of loess is slightly thinner than the loess covering the adjacent uplands and depressions. Where they have been cored, the ridges underlying the loess consist of well-sorted sand on the order of thick. Also buried by loess beneath the surface of the Rainwater Basin wetland region are the relict channel belt of the Pleistocene Platte River and relict fields of sand dunes. The original Rainwater Basins are associated with both of these buried Pleistocene landscapes. The age of the loesses and associated paleosols that buried the original Rainwater basins and the fluvial sand in which they formed have been dated by either radiocarbon dating,

optically stimulated luminescence dating Luminescence dating refers to a group of methods of determining how long ago mineral grains were last exposed to sunlight or sufficient heating. It is useful to geologists and archaeologists who want to know when such an event occurred. It uses var ...

, or both. The oldest loess overlying original Rainwater basins have yielded ages from about 28,000 to 36,000 BP radiocarbon years and optically stimulated luminescence up to 36,000 BP calendar years.Maat, P.B. and Johnson, W.C., 1996. ''Thermoluminescence and new 14C age estimates for late Quaternary loesses in southwestern Nebraska.'' ''Geomorphology'', 17(1-3), pp.115-128.Muhs, D.R., E.A. Bettis III, J.N. Aleinikoff, J.P. McGeehin, J. Beann, G. Skipp, B.D. Marshall, H.M. Roberts, W.C. Johnson, and R. Benton. (2008
''Origin and paleoclimatic significance of late Quaternary loess in Nebraska: Evidence from stratigraphy, chronology, sedimentology, and geochemistry.''
Geological Society of America Bulletin. 120(11/12):1378–1407. The fluvial sands of a pleistocene Platte River, which overlain by the Gilman Canyon formation and younger loesses, yielded optically stimulated luminescence dates from about 36,000 to 50,000 BP calendar years. These dates demonstrate that the Rainwater basins were formed prior to the Middle Wisconsinan, Marine Isotope Stage 3, and the accumulation of the Gilman Canyon Formation. Thus, Rainwater basins and their associated ridges are relict, pre-

Last Glacial Maximum The Last Glacial Maximum (LGM), also referred to as the Late Glacial Maximum, was the most recent time during the Last Glacial Period that ice sheets were at their greatest extent. Ice sheets covered much of Northern North America, Northern Eur ...

landforms that have migrated upward in elevation as successive layers of glacial-age loess have accumulated and intercalated soils sporadically formed.Johnson, W.C., Hanson, P.R., Halfen, A.F. and Koop, A.N., 2020. ''The Central and Southern Great Plain''. In ''Inland Dunes of North America'' (pp. 121-179). Springer Nature, Switzerland. https://doi.org/10.1007/978-3-030-40498-7_4

References

External links