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Little Washita River Experimental Watershed
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Situated between Chickasha and Lawton in southwestern Oklahoma, the Little Washita River watershed comprises 600 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.

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 recently has been upgraded and re-instrumented to measure rainfall, air and soil temperatures, relative humidity, and solar radiation.

In the 1990's Little Washita River watershed and its parent basin became one of three concentrated study sites for the ARS research program entitled "Global Change, Water Resources and Agriculture".

In 2003 the Little Washita River Experimental Watershed was chosen as one of Conservation Effects Assessment Project, CEAP, study sites.  And later as the pilot watershed for the CEAP database.

In the early 1990's ARS began monitoring the environmental conditions of the Little Washita watershed with a 42-station network called the ARS 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.

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
Minimum elevation - about 300 meters
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


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


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.