The Rainwater Basin wetland region is a

loess A loess (, ; from ) is a clastic rock, 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 loesses or similar deposition (geology), deposits. A loess ...

plain located south of the Platte River in south-central

Nebraska Nebraska ( ) is a landlocked U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Ka ...

.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 Prairies are ecosystems considered part of the temperate grasslands, savannas, and shrublands biome by ecologists, based on similar temperate climates, moderate rainfall, and a composition of grasses, herbs, and shrubs, rather than trees, as the ...

grassland A grassland is an area where the vegetation is dominance (ecology), dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes such as clover, and other Herbaceo ...

s interspersed with thousands of ephemeral playa

wetland A wetland is a distinct semi-aquatic ecosystem whose groundcovers are flooded or saturated in water, either permanently, for years or decades, or only seasonally. Flooding results in oxygen-poor ( anoxic) processes taking place, especially ...

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 The tallgrass prairie is an ecosystem native to central North America. Historically, natural and Historical ecology#Anthropogenic fire, anthropogenic fire, as well as grazing by large mammals (primarily bison) provided periodic disturbances to th ...

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 botanical diversity than either the tall- or shortgrass prairie. The mixed-grass prairie occurs in the Cen ...

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

corn Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout Poaceae, grass that produces cereal grain. It was domesticated by indigenous peoples of Mexico, indigenous peoples in southern Mexico about 9,000 years ago ...

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. Soy is a staple crop, the world's most grown legume, and an important animal feed. Soy is a key source o ...

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 strea ...

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 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, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

.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 of plants) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has bee ...

. 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 from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, rain and snow mixed ("sleet" in Commonwe ...

, 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 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 landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States, Western United States. It borders Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho t ...

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. 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 Birdwatching, or birding, is the observing of birds, either as a recreational activity or as a form of citizen science. A birdwatcher may observe by using their naked eye, by using a visual enhancement device such as binoculars or a telescop ...

; 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 ...

Canada goose The Canada goose (''Branta canadensis''), sometimes called Canadian goose, is a large species of 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 A ...

* Killdeer * Least sandpiper *

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

* Northern pintail *

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 throughout the Palearctic and across most of North America, and winters in southe ...

Peregrine falcon The peregrine falcon (''Falco peregrinus''), also known simply as the peregrine, is a Cosmopolitan distribution, cosmopolitan bird of prey (raptor) in the family (biology), family Falconidae renowned for its speed. A large, Corvus (genus), cro ...

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

Sandhill crane The sandhill crane (''Antigone canadensis'') is a species of large Crane (bird), cranes of North America and extreme northeastern Siberia. The common name of this bird refers to its habitat, such as the Platte River, on the edge of Nebraska's S ...

Snow goose The snow goose (''Anser caerulescens'') is a species of goose native to North America. Both white and dark morphs exist, the latter often known as blue goose. Its name derives from the typically white plumage. The species was previously placed ...

* White-fronted goose * Greater and lesser yellowlegs

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 encompasses crop and livestock production, aquaculture, and forestry for food and non-food products. Agriculture was a key factor in the rise of sedentary human civilization, whereby farming of domesticated species created f ...

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 A river is a natural stream of fresh water that flows on land or inside caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of its course if it ru ...

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

s and

gravel Gravel () is a loose aggregation of rock fragments. Gravel occurs naturally on Earth as a result of sedimentation, sedimentary and erosion, erosive geological processes; it is also produced in large quantities commercially as crushed stone. Gr ...

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

es and associated

paleosol In Earth science, geoscience, paleosol (''palaeosol'' in Great Britain and Australia) is an ancient soil that formed in the past. The definition of the term in geology and paleontology is slightly different from its use in soil science. In geo ...

s. The loess, which overlies these features, consists of an undisturbed sequence, from bottom to top, of Middle Wisconsinan 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 geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...

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, 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 Marine isotope stages (MIS), marine oxygen-isotope stages, or oxygen isotope stages (OIS), are alternating warm and cool periods in the Earth's paleoclimate, deduced from Oxygen isotope ratio cycle, oxygen isotope data derived from deep sea core ...

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 Last Glacial Coldest Period, was the most recent time during the Last Glacial Period where ice sheets were at their greatest extent between 26,000 and 20,000 years ago. Ice sheets covered m ...

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

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