The spatial and temporal variability of hydrologic, climatic, and ecosystem processes and their interactions require the use of distributed-parameter models that can incorporate this variability. The Modular Modeling System (MMS) is an integrated system of computer software that has been developed to provide the research and operational framework needed to support development, testing, and evaluation of water, energy, and biogeochemical process algorithms and to facilitate integration of user-selected sets of algorithms into an operational model. MMS uses a master library that contains user-developed, compatible modules for simulating these processes and which can be linked using MMS tools to create a model.
A geographic information system (GIS) interface has been developed for MMS to support a variety of GIS tools for use in the (1) delineation, characterization, and parameterization of topographic, hydrologic, and ecosystem features, (2) visualization of spatially and temporally distributed module parameters and variables, and (3) analysis and validation of parameter estimates and model results. The GIS tools have been developed for use with Arc/Info and GRASS. They utilize a variety of digital databases and digital elevation models to provide a number of objective characterization and parameterization techniques for application over a range of spatial and temporal scales. Specific combinations of techniques can be linked with MMS modules to automate the estimation of selected module parameters and write these estimates to a model parameter file prior to module execution. The GIS toolset is demonstrated for a hydrologic and ecosystem management model application on the South Fork McKenzie River, Oregon.