We present a model of the plasma and neutral environment that treats plasma and neutrals self-consistently, using Voyager plasma and ultraviolet H observations and Hubble Space Telescope OH measurements as constraints. The neutral distributions are determined with a Monte Carlo model, and the plasma distributions are determined with a diffusive transport model including sources and losses. We find a larger percentage of molecular ions than in previous work, that H2O is the dominant neutral near the satellite sources but OH is dominant elsewhere, and that the total H2O source required is 1028 H2O/s, a factor of 3 larger than previously thought. The large amount of water appears to emanate from Enceladus's orbital distance, and the production mechanism remains unclear. We produce density contours for each neutral species and discuss the implications of these results in anticipation of new data from Cassini.