Purpose Once the land use, soil, and slope data layers have been imported overlaid, the distribution of hydrologic response units (HRUs) within the watershed must be determined. The HRUs Definition command in the HRU Analysis menu allows the user to specify criteria used in determining the HRU distribution. One or more unique land use/soil/slope combinations (hydrologic response units or HRUs) can be created for each subbasin. Application Subdividing the watershed into areas having unique land use and soil combinations enables the model to reflect differences in evapotranspiration and other hydrologic conditions for different land covers/crops and soils. Runoff is predicted separately for each HRU and routed to obtain the total runoff for the watershed. This increases the accuracy of load predictions and provides a much better physical description of the water balance. The user has two options in determining the HRU distribution: assign a single HRU to each subwatershed or assign multiple HRUs to each subwatershed. If a single HRU per subbasin is selected, the HRU is determined by the dominant land use category, soil type, and slope class within each watershed. If multiple HRUs are selected, the user may specify sensitivities for the land use, soil, and slope data that will be used to determine the number and kind of HRUs in each watershed. Key Procedures Select single or multiple HRUs per subwatershed For multiple HRUs, define land use and soil threshold levels Optional: Set land use refinement parameters to split HRU land use classes and define special land uses exempt from threshold levels Click the OK button to determine the HRU distribution Detailed Operations