3. MATERIAL AND METHODS
3.1 Data
Precipitation and temperature data collected by the National Climate Data Center (NCDC) of the National Oceanic and Atmospheric Administration (NOAA) and United States Department of Agriculture (USDA) were used in our study. The annual total precipitation and annual mean temperature were calculated from daily data and used to analyze changes in temperature and precipitation from 1970 - 2009. Stream flow data were obtained from the National Water Information System (NWIS) of the US Geological Service (USGS). The one gauge station (07226500) in the study area has provided continuous daily data from 1970 - 2009 and is located at the outlet of the upper Canadian River watershed. Soil data for the study area was obtained from the State Soil Geographic (STATSGO) database. The STATSGO is a digital soil map created in 1994 by the Natural Resources Conservation Service (NRCS). In addition to the above data sets, a Digital Elevation Model (DEM) with a 30-m spatial