Introduction

This chapter reviews the challenges of global water supply and demand in a changing environment. Human efforts have been made over the last decades to manage water resources and to preserve natural water environment. The use of water environment models has been an essential part of these efforts. Successful applications of surface and groundwater models for assessing water quality deterioration and formulating remedial actions are illustrated. This chapter also discusses the modeling uncertainties due to unsatisfactory calibration of model parameters and presents the modeling procedures that need to be followed to reduce these uncertainties. At the end of this chapter, perspectives of water environment modeling are briefly discussed.