1. Integrated modeling in the Little Washita basin
  2. Study area and data
The study area is in the size of about 1600 km2 (41 km × 41 km) that includes the Little Washita basin (~ 600 km2) (Figure 2). It is in the southwestern Oklahoma of the U.S., characterized by the semi-arid climate. The elevation varies from 330 m to 460 m, which is lower in the northeast while higher in the west and southeast (Figure 2a). The land cover (Figure 2b) is dominated by grasslands and savannas, belonging to the classification of International Geosphere-Biosphere Program (IGBP) (https://www.usgs.gov/centers/eros). Croplands are found along the stream while a small portion of forests is scattered in the west (Figure 2b). The top soil (Figure 2c), determined from Miller and White (1998), is composed by the loam and loamy sand and a small portion of sand and silt loam (Kollet and Maxwell, 2008; Condon and Maxwell, 2014a). Hydraulic conductivities of the deep aquifers (Figure 2d) are within a range of 0.025–0.689 m/hr (Condon and Maxwell, 2014a), which are determined from the global permeability in Gleeson et al. (2011) with adjustment from the borehole observation data (Kollet and Maxwell, 2008).
The data listed above and the basic framework of the model used in this study are adopted from the installation package of ParFlow.CLM (https://github.com/parflow/parflow). Nevertheless, the modeling area is a real place and the above data either have publicly accessible sources or are available from previous studies. Specific modifications mainly on the coupling depth are done in this study. Previous studies conducted in this basin also include, e.g., Kollet and Maxwell (2008), Ferguson and Maxwell (2011 and 2012), and Condon and Maxwell (2014a and 2014b), which indeed can be taken as a benchmarking case for further explorations.