Evaluation of Flows Simulated with Regional Parameters at Tinley Creek Watershed, Illinois

Accuracy of simulated flows resulting from applying transferred rainfall-runoff parameters is evaluated with observed flows from Tinley Creek watershed (28.67 km²) in northeastern Illinois. Two previously calibrated rainfall-runoff parameter sets (Current and CTE) for the Hydrological Simulation Program-FORTRAN (HSPF) model developed in a separate watershed, are applied in the evaluation. In the watershed model development, watershed land-use data are obtained from digitizing the 2005 enhanced aerial photos according to the 11 land-cover categories used in the previous studies. The evaluation simulation period was from October 1996 to September 2003. An analysis of the percentage of effective impervious area is also reported. Rainfall-runoff correlation, runoff coefficients, and simulated sub-surface runoff volumes, in addition to surface runoff volumes are examined. Results indicate that the Current parameter set estimated higher evapotranspiration than the CTE parameter set, and therefore lower surface-runoff volumes were simulated. The Current parameter set simulated less infiltration and interflows, but more groundwater storage and groundwater runoffs than the CTE parameter set. Comparison of the ratio of simulated to recorded flow records (S/R ratio) indicates that the CTE parameter set is more suitable than the Current parameter set for simulating flows in this watershed. The overall S/R ratio for Tinley Creek is 0.85 for the simulation period.