The user must supply more than 100 individual inputs, some of which require considerable judgment to estimate. Additionally, there are three data groups for simulation control and uncertainty analysis. The stream system should be divided into reaches, which are stretches of stream that have uniform hydraulic characteristics. Each reach is then subdivided into computational elements of equal length. Thus, all reaches must consist of an integer number of compu- tational elements.
River reaches are the basis of most input data.
The global variables include simulation variables, such as units and simulation type, water quality con- stituents, and some physical characteristics of the basin. Up to 15 water quality constituents can be modeled by QUAL2E. Forcing functions are user-specified inputs that drive the system being modeled. These inputs are speci- fied in terms of flow, water quality characteristics, and local climatology. Local climatological data are required for the simulation of algae and temperature. The temperature simulation uses a heat balance across the air-water interface and thus requires values of wet and dry bulb air temperatures, atmospheric pressure, wind velocity, and cloud cover.