EFFICACY OF ARC INFO GIS APPLICATION TO HYDROLOGIC MODELING/

A hypothetical water shed was constructed to test the efficacy of usin g the ARC/INFO geographic information system to provide spatially rela ted input for the U.S. Army Corps of Engineers HEC-1 hydrologic model. The ARC/INFO system performed the tedious and time-consuming tasks of spatial averaging (basin areas, average runoff curve numbers. etc.) q uite well. Difficulties, however, were encountered in using the TIN (t riangulated irregular network) module to accurately assess average rai nfall intensities. The inaccuracies associated with the computation of average basin rainfall intensities were quantified by using a defined rainfall pattern imposed upon a simple geometric shape (equilateral t riangle) and were found to be directly related to the number of prescr ibed contouring intervals. The highest density of contouring intervals (0.010 nm) resulted in only a 0.55% overestimation. The number and lo cation of rain gages relative to watershed boundaries imparted a signi ficant error (approximately +/- 10%) to average rainfall estimation.