HYDROLOGIC MODEL FOR DRAINED FOREST WATERSHED

Modeling the hydrology of a forest watershed is helpful to understand the interaction of the hydrologic components and the effects of management activities on the performance of the system. This study was conducted to develop a hydrologic model for a drained loblolly pine (Pinus taeda) plantation watershed. Rainfall interception, subsurface drainage, and evapotranspiration models characterizing a forest watershed are described and incorporated into DRAINMOD, a hydrologic model originally developed for poorly drained agricultural fields. Simulation results are compared with measured field data collected in 1988-1989 from an intensively monitored experimental forest watershed in the coastal plain of North Carolina. Estimated drainage rates and water-table elevations agreed well with those measured on each of three watersheds. Estimated cumulative drainage volumes for a 672-day period were within 2-9% of measured values. The estimated water-table elevations had an absolute average deviation of 20-22 cm for the 672-day period. The model adequately describes the hydrology of the forest system and will be an important analytical tool in evaluating alternative forest water management systems and in developing best management practices that take into account both off-site and on-site impacts.