Here is some practical advice I cull from Hydrology and Floodplain Analysis (1988) by Philip B. Bendient and Wayne C. Huber. They recommend the following steps in using models to simulate and analyze surface water management problems:
• Obtain all necessary input data: rainfall, infiltration, physiography, landuse, channel characteristics, streamflow, design floods, and reservoir data.
• Evaluate and refine study objectives in terms of simulations to be performed under various watershed conditions.
• Choose methods for determining subbasins hydrographs and channel routing.
• Calibrate model using historical rainfall, streamflow, and existing watershed conditions. Verify model using other events under different conditions while maintaining same calibration parameters.
• Perform model simulations using historical or design rainfall; various conditions of land use; various control schemes for reservoirs, channels, and diversion facilities.
• Perform sensitivity analysis on input data, routing parameters, and hydrograph parameters.
• Evaluate usefulness of the model and comment on needed changes or modifications.