Operational water management is a day-by-day activity that requires among other things,
predicting the state and response of hydrologic systems. Improving these predictions,
even on relatively short time-scales, has clear societal benefit as it allows for
improved flood warning and reservoir management. Consequently, the development of
improved hydrologic predictions and applications has been identified as an important
scientific priority of an array of national research programs.
When a hydrologic system is deemed "predictable",
hydrologic predictions can be developed using a wide range of models that accept
measurements of current conditions, and forecast of future conditions as input and
project the future state of the hydrologic system and its response to these forcing
variables. Hydrologic Models range in complexity from simple rainfall-runoff
transformation equations to those based on mathematical representation of the
complex interactions between land surface, soil, vegetation, and the atmosphere
(commonly called Land-Surface Models).