Simulation of Runoff Generation in Hydrologic Models

Refer to Chapter 6 of the Rainfall Runoff Processes Workbook

The understanding of rainfall-runoff processes that you have learned in the previous sections is intended to provide the basic knowledge necessary to understand the physical rainfall runoff processes and relate this understanding to the necessarily simplified representation adopted by rainfall-runoff models used in practice.   In this section we review some of the key ideas in rainfall-runoff models so that you can appreciate the physical basis for the conceptual process representations used by the models.  The essential feature of a simulation model is that it produces an output or series of outputs in response to an input or series of inputs.  In the case of a rainfall-runoff model the inputs are characteristics of the watershed being modeled, such as drainage area and channel network geometry, topography, soil and land use characteristics and a time series of surface water input.  The output is a time series of streamflow at an outlet location. 

The quantity and diversity of geospatial and environmental data is increasing, requiring increasingly sophisticated geographic information systems (GIS) to organize and manage this data.  The abundant availability of data and the computing power to move it around is changing the way hydrologic modeling is done.  We are moving from being data limited to being overwhelmed by data.  Hydrologic models are evolving to take advantage of the increasing data availability by incorporating the spatial variability of factors that influence hydrologic response, such as topography and soils that you have learned about in this module.