ABSTRACT
Aims: Provide a review of key features and several applications of the family of Integrated Water Resources (IWR) models, as the key analytical tools used in evaluation of hydrologic conditions in support of the integrated regional water management (IRWM) programs in California. Methodology: IWR models are a family of models consisting of the Integrated Groundwater and Surface water Model (IGSM), the Integrated Water Flow Model (IWFM), and the IWFM Demand Calculator (IDC). IGSM is an integrated model that simulates the complete hydrologic cycle for a basin. The California Department of Water Resources (CADWR) has upgraded and enhanced the IGSM code and developed an enhanced version, called IWFM. In addition, CADWR extracted the land surface processes module of IWFM as an independent unit, called IDC, which can be used as a stand-alone model for estimating agricultural water demand, groundwater pumping, and deep percolation. The IWR models have been applied to many basins throughout California to evaluate hydrologic conditions, including evaluation of land and water use, surface water and groundwater flow, stream-aquifer interaction, reservoir operation, land subsidence, and regional water quality conditions. An ArcGIS-based Graphical User Interface provides a robust modeling platform for the IWR models. Results: The IWR models have had significant success in analysis of various types of water resources projects, such as integrated regional water management programs, groundwater management and conjunctive use operations, groundwater recharge investigations, water transfer programs, water quality, water demand and supply analysis, seawater intrusion, and climate change vulnerability and adaptation analysis. Conclusion: The IWR models are effective tools in analyzing the technical issues involved in integrated water management and planning in California. These IWR models are well suited for analysis of hydrologic conditions and alternative water management scenarios explored in various basin management and IRWM programs.