Define the usage of Data from Hydrographs

• Flow rates and volume quantities over time.
• Predictions based on the runoff flow rates. The characteristics of the drainage basin/watershed/collection system areas determine the shapes of the hydrographs. For example, the steepness of the "rising limb" of a hydrograph can be used to predict the response time needed before flooding occurs in low elevation areas.
• The maximum flow rates (crest) and the time this will occur.
• The rate at which flow will decrease and return to normal.
• Base flow rates. Using the hydrograph separation method, base flow rates can be identifies and separated from surface runoff. Base flow is the ground water contribution in streams, and it is the inflow and infiltration in sewer collection systems.
• The volume of the runoff generated by a storm = area under the overland flow/storm/surface water only hydrograph.
• Precipitation (inches) = surface water volume (ft³)/drainage basin area (ft²).
• For a given watershed, the shape and plot points of a "unit hydrograph" will ratio to the plot points for a storm hydrograph at the same time.