A computer model is developed and calibrated for simulating the movement of water and H ion through a forested watershed. The model is appropriate to a small (1 km<latex>$^2$</latex>) non-calcareous basin. The model is run on a daily time step with meteorological and pH of precipitation inputs. The model incorporates acid neutralizing capacity (a.n.c.) for various soil horizons. Changes in field capacity on the short and long term (weeks and months) and change in the hydraulic conductivity of the saturated zone on the long term affect basin outflow; a.n.c. and depth of the soil affect the pH of water on the long term. Reasonable changes in snow leaching, canopy enrichment, a.n.c., soil depth and total soil thickness have no effect on pH in the short term.