The Precipitation-Runoff Modeling System (PRMS) model of the U.S. Geological Survey was used to simulate the hydrologic effects of timber management in 11 small, upland drainage basins of the Coast Range in Oregon. The coefficients of determination for observed and simulated daily flow during the calibration periods ranged from 0.92 for the Flynn Creek Basin to 0.68 for the Priorli Creek Basin; percent error ranged from -0.25 for the Deer Creek Basin to -4.49 for the Nestucca River Basin. The coefficients of determination during the validation periods ranged from 0.90 for the Flynn Creek Basin to 0.66 for the Wind River Basin; percent error during the validation periods ranged from -0.91 for the Flynn Creek Basin to 22.3 for the Priorli Creek Basin. In addition to daily simulations, 42 storms were selected from the time-series periods in which the 11 basins were studied and used in hourly storm-mode simulations. Sources of simulation error included the quality of the input data, deficiencies in the PRMS model-algorithms, and the quality of parameter estimation. Times-series data from the Flynn Creek and Needle Branch Basins, collected during an earlier U.S. Geological Survey paired-watershed study, were used to evaluate the PRMS as a tool for predicting the hydrologic effects of timber-management practices. The Flynn Creek Basin remained forested and undisturbed during the data-collection period, while the Needle Branch Basin had been clearcut 82 percent at a midpoint during the period of data collection. Using the PRMS, streamflow at the Needle Branch Basin was simulated during the postlogging period using prelogging parameter values. Comparison of postlogging observed streamflow with the simulated data showed an increase in annual discharge volume of approximately 8 percent and a small increase in peak flows of from 1 to 2 percent. The simulated flows from the basins studied were generally insensitive to the number of hydrologic-response units used to replicate basin surface detail. The average number of hydrologic-response units used in the storm-period simulations was one-half the average number of hydrologic-response units used in the daily period simulations. With the exception of one basin, however, the coefficient of determination between observed and simulated daily flow differed by only 3 percent. Calibration and validation of the PRMS for 11 basins--that encompass a variety of forest, soil, and topographic conditions--provided regionalized parameter values. The parameter values assist the PRMS hydrologic simulations of other gaged and ungaged basins in the Coast Range with landscape conditions similar to those of the basins studied.
Additional publication details
USGS Numbered Series
Use of a precipitation-runoff model for simulating effects of forest management on streamflow in 11 small drainage basins, Oregon Coast Range
Water-Resources Investigations Report
U.S. Dept. of the Interior, U.S. Geological Survey ;
U.S. Geological Survey, Earth Science Information Center, Open-File Reports Section [distributor],