APPLICATION OF REGIONAL PARAMETER-ESTIMATION SCHEMES TO SIMULATE THE WATER-BALANCE OF A LARGE CONTINENTAL RIVER

Two applications of a grid network version of the two-layer variable i nfiltration capacity (VIC-2L) land surface hydrology model applied at one degree resolution to the Arkansas-Red River basin are compared. In the first application, gridded parameter fields were linearly interpo lated from locally estimated parameters (via a search procedure) at a set of 40 unregulated catchments distributed throughout the Arkansas-R ed River basin with long-term gage records. In the second application, the grid network model was run using the same precipitation and poten tial evapotranspiration as in the first application, but with paramete rs transferred to the large area grid from the gaged catchments via re gression of the locally estimated parameters on catchment soils, topog raphic, and climatological characteristics. In both cases, the model w as run at a daily time-step, and vegetation parameters were tired (wit h prescribed seasonal variation but no interannual variation in the ca se of leaf area index). Generally, the simulations based on the region al regression transfer scheme performed significantly better than thos e based on the interpolated parameters; at the mouth of the Arkansas t he absolute simulation error for annual flows was reduced from 7.3 to 1.3%, and for the Red, it was reduced from 12 to 1.7%. However, the ba sin-wide annual evapotranspiration and its seasonal cycle were relativ ely insensitive to the hydrological parameter estimation schemes. (C) 1997 Elsevier Science B.V.