ABSTRACT

In addition to long time scales, many of the models used to simulate groundwater problems, and models that integrate groundwater systems with other parts of the hydrologic environment, have lengthy execution times. us, the computational demands of the dierent methods presented in this chapter are noted and methods that range from computationally frugal (generally requiring 10s to 100s of parallelizable model runs) to computationally demanding (requiring 10,000 or more models runs and sometimes with limited parallelizability) are discussed. In general, there is a tradeo in using the computationally frugal to demanding methods. More frugal methods tend to be accompanied by more restrictive assumptions about simulated results being a smooth function of parameter values and errors being close to Gaussian simulation. Demanding methods tend not to be encumbered by such restrictions. Computationally frugal tests able to identify when dierent

21.1 Introduction .............................................................................................................................597 21.2 Use Data to Test Models .........................................................................................................598