Introduction

Abstract

In this chapter, commonly seen models in environmental and water resources (EWR) study are shown. A general form of mathematical models and their classifications are then provided. Different mathematical models are constructed across different science and engineering disciplines. Models used in the EWR fields are often nonlinear, dynamic, stochastic, and governed by partial differential equations. The traditional process of constructing a EWR model involves data collection, conceptualization, model calibration/parameter estimation, and finally, the evaluation of model reliability. Data types available for model construction include prior information, direct measurements of parameters, observations of state variables, as well as the accuracy requirement of model applications. Depending on data types, different approaches and criteria for model calibration and parameter estimation exist. The model complexity problem, model reliability problem, and data sufficient problem must be considered systematically other than separately or sequentially during the model construction stage.