Overview

Situated between Chickasha and Lawton in southwestern Oklahoma, the Little Washita River watershed comprises 611 square kilometers and covers parts of Caddo, Comanche, and Grady counties. The Little Washita River is a tributary of the Washita River, which drains into the Red River on the Oklahoma-Texas border. Hydrological and meteorological measurements of the watershed have been conducted for decades, providing scientists a long-term data source to study soil and water conservation, water quality, and basin hydrology. Currently, the ARS monitors the environmental conditions of the Little Washita watershed with a 20-station network called the Little Washita Micronet. In addition, three stations in the Oklahoma Mesonet (NINN, ACME, and APAC) are located in the northeast, south, and west areas of the watershed to enhance the observing network.

The Ft. Cobb Reservoir watershed comprises 813 square kilometers and covers parts of Caddo, Washita, and Custer counties in southwestern Oklahoma. The Ft. Cobb Micronet consists of 15 stations, which measure the same variables as the Little Washita Micronet. Two Oklahoma Mesonet sites (FTCB and HINT) are located on the southern and northern sides of the watershed.

Scientific Research

In 1936, the Little Washita watershed was selected as a part of a national demonstration project for soil erosion control. Since then, continuous observations of the watershed have been taken in a variety of hydrologic research projects. The U.S. Department of Agriculture (USDA) Agricultural Research Service (ARS) began collecting data on the Little Washita in 1961. Their goal was to examine the downstream impacts of Soil Conservation Service floodwater-retarding reservoirs. To that end, a network of 36 continuous recording rain gauges were deployed on the watershed.

Almost two decades later, in 1978, this watershed was one of seven selected for a national project that was jointly administered by the USDA and the U.S. Environmental Protection Agency (EPA). In this case, the project's goal was to demonstrate the effects of intensive land conservation treatments on the quality of water in the watershed. Although field measurements were reduced from 1985 to 1992, the network of sensors was expanded, upgraded, and re-instrumented in 1994 to measure rainfall, air and soil temperatures, relative humidity, and solar radiation.

The Ft. Cobb watershed was added to the ARS watershed research network in 2005 to address research objectives of the Conservation Effectiveness Assessment Project (CEAP). CEAP is a USDA Natural Resources Conservation Service sponsored program, which seeks to quantify the effectiveness of Federal Conservation practices, at watershed scales, to reduce constituents that impair water quality and wildlife habitat.

Facts about the Little Washita watershed

Size: 611 square kilometers
Watershed studies began: 1936
Land usage: range, pasture, forest, cropland, oil waste land, quarries, urban/highways, and water

Topography and geology

Maximum elevation: about 500 meters above sea level
Minimum elevation: about 300 meters above sea level
Exposed bedrock: Permian age sedimentary rocks; sandstone dominant
Soil textures: range from fine sand to silty loam
SCS hydrologic group: group B covers nearly three-fourths of the watershed
Surface drainage: generally eastward

Climate

Mean annual precipitation: 760 millimeters
Mean annual temperature: 16 degrees Celsius
Daily average maximum temperature, January: 10 degrees Celsius
Daily average minimum temperature, January: -4 degrees Celsius
Daily average maximum temperature, July: 35 degrees Celsius
Daily average minimum temperature, July: 21 degrees Celsius
For more information, see Oklahoma Climate Data

Facts about the Ft. Cobb watershed

Size: 813 square kilometers
Watershed studies began: 2005
Land usage: cropland, range, pasture, forest, water, and urban/highways

Topography and geology

Maximum elevation: about 565 meters
Minimum elevation: about 383 meters
Exposed bedrock: Permian age sedimentary rocks; sandstone dominant
Soil textures: XXXX
SCS hydrologic group: XXXX
Surface drainage: generally southeastward

Climate

Mean annual precipitation: 816 millimeters
Mean annual temperature: 16 degrees Celsius
Daily average maximum temperature, January: 10 degrees Celsius
Daily average minimum temperature, January: -4 degrees Celsius
Daily average maximum temperature, July: 36 degrees Celsius
Daily average minimum temperature, July: 22 degrees Celsius
For more information, see Oklahoma Climate Data

Reference

Elliott, R.L., F.R. Schiebe, K.C. Crawford, K.D. Peter and W.E. Puckett. 1993. A Unique Data Capability for Natural Resources Studies. Paper No. 932529, International Winter Meeting; American Society of Agricultural Engineers, Chicago, IL, Dec. 14-17.

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