Hydrologic modeling in arid areas: Concepts, theory and data

Water resources are strategic national resources and development of knowledge to enable their sustainable management and use must be a high national priority. It is impossible to monitor all of our watersheds, yet we need the ability to predict the consequences of land use and management decisions on watershed resources before use and management is undertaken. Simulation models provide the mechanism for this prediction ability. Water balance modeling is used to illustrate the application of simulation modeling to management of arid watersheds. Arid environments are characterized by extreme hydrologic variability. Simulation models can mimic this variability, but have their conceptual and practical limitations. Major challenges to overcome these limitations and improve our ability to predict water balances in arid environments are identified and discussed.