BROOK90 is a hydrological model that simulates vertical soil water movement and daily evapotranspiration for all land surfaces at all times of year using a process-oriented approach with physically-meaningful parameters. The complexities of hillslope hydrology and spatial distribution have been omitted in order to focus on the details of the factors controlling evaporation. The model estimates interception and transpiration from a single layer (big leaf) plant canopy, soil and snow evaporation, snow accumulation and melt, and soil-water movement through one or more soil layers (including macropore-assisted infiltration).