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Title: Soils, crop production, and geology in the Fort Cobb reservoir watershed, southwestern Oklahoma

Author
item Starks, Patrick
item Daniel, John
item Moriasi, Daniel

Submitted to: USGS - Scientific Investigations Report
Publication Type: Other
Publication Acceptance Date: 7/15/2011
Publication Date: 9/20/2011
Citation: Starks, P.J., Daniel, J.A., Moriasi, D.N. 2011. Soils, crop production, and geology in the Fort Cobb reservoir watershed, southwestern Oklahoma. In: Becker, C.J. (ed.). Assessment of Conservation Practices in the Fort Cobb Reservoir Watershed, Southwestern Oklahoma. USGS - Scientific Investigations Report. Available: http://pubs.usgs.gov/sir/2010/5257.

Interpretive Summary: The Ft. Cobb Reservoir Experimental Watershed (FCREW) is one of 14 ARS benchmark CEAP (Conservation Effects Assessment Project) watersheds. To address basic CEAP research questions, and to foster interagency research collaborations, several spatial data sets and data from various field experiments were analyzed and compiled for inclusion in a governmental report characterizing the soils, geology, agriculture, landscape dynamics, biology, and ecology of the watershed. In this particular chapter, the soils and geology of the watershed are described. Analysis of the distribution of soils in the watershed indicates that water and any associated contaminants (agri-chemicals, septic system effluent, etc.) will move at a faster rate through the sandy soils of the Willow Creek and Lake Creek sub-watersheds than through the silt soils located further west in the Cobb Creek sub-watershed. About 20% of the FCREW is overlain by highly erosive soils of the Dougherty, Eufaula, and Konawa series. Theses soils have the highest sand fractions (87%) of all the soil series found in the watershed and have the highest saturated hydraulic conductivity observed in the STATSGO database for this watershed. Geologically, the Rush Springs and the Cloud Chief formations are the two primary rock units outcropping in the FCREW. The Rush Springs Formation is a major aquifer in central Oklahoma covering an area of 4765 square kilometers (1840 square miles), and is the principal rock unit outcropping in the Fort Cobb region. It consists of friable reddish brown, cross-bedded to regular-bedded sandstone and can reach a thickness of 102m (334 feet). Because of its thickness, extent, and hydrologic character, it is a major aquifer and a drinking water source for some municipalities and for agricultural irrigation. The formation is porous and permeable and yields good quantities of water. The Cloud Chief Formation is a minor rock unit in the Fort Cobb watershed and forms cap rock on many buttes or hills, and consists of a thin veneer of impure dolomite, gypsum, gypsiferous sandstone and shale. The base of the Cloud Chief formation consists of a layer of gypsum (the Weatherford Gypsum) which overlies the Rush Springs Formation. The water yield of the Cloud Chief Formation is low because of the high clay content.

Technical Abstract: The Ft. Cobb Reservoir Experimental Watershed (FCREW) is one of 14 ARS benchmark CEAP (Conservation Effects Assessment Project) watersheds. To address basic CEAP research questions, and to foster interagency research collaborations, several spatial data sets and data from various field experiments were analyzed and compiled for inclusion in a governmental report characterizing the soils, geology, agriculture, landscape dynamics, biology, and ecology of the watershed. In this particular chapter, the soils and geology of the watershed are described. Analysis of the distribution of soils in the watershed indicates that water and any associated contaminants (agri-chemicals, septic system effluent, etc.) will move at a faster rate through the sandy soils of the Willow Creek and Lake Creek sub-watersheds than through the silt soils located further west in the Cobb Creek sub-watershed. About 20% of the FCREW is overlain by highly erosive soils of the Dougherty, Eufaula, and Konawa series. Theses soils have the highest sand fractions (87%) of all the soil series found in the watershed and have the highest saturated hydraulic conductivity observed in the STATSGO database for this watershed. Geologically, the Rush Springs and the Cloud Chief formations are the two primary rock units outcropping in the FCREW. The Rush Springs Formation is a major aquifer in central Oklahoma covering an area of 4765 square kilometers (1840 square miles), and is the principal rock unit outcropping in the Fort Cobb region. It consists of friable reddish brown, cross-bedded to regular-bedded sandstone and can reach a thickness of 102m (334 feet). Because of its thickness, extent, and hydrologic character, it is a major aquifer and a drinking water source for some municipalities and for agricultural irrigation. Porosity averages 32%, with a specific yield of 25% and permeability of 1222 l/day/m 2 (30 g/day ft 2). The Cloud Chief Formation is a minor rock unit in the Fort Cobb watershed and forms cap rock on many buttes or hills, and consists of a thin veneer of impure dolomite, gypsum, gypsiferous sandstone and shale. The base of the Cloud Chief formation consists of a layer of gypsum (the Weatherford Gypsum) which unconformably overlies the Rush Springs Formation. The water yield of the Cloud Chief Formation is low because of the high clay content.