Content area
Full Text
1. Introduction
Understanding the characteristics of water fluxes and storages across regions and globally and their future trajectories is crucial to plan and manage sustainable water use under changing climate and growing population.
Various models, particularly global land surface models and global hydrological models, are used for modeling regional and global water fluxes and storages under present and future climate conditions (Fung et al. 2011; Haddeland et al. 2011; Warszawski et al. 2014). The climate community uses land surface models developed to provide lower boundary conditions for general circulation models by solving the surface energy balance. A main focus of the land surface models is to estimate actual evapotranspiration (ET), which is a key component of the global energy and water cycle (Jung et al. 2010). The hydrology community uses global hydrological models that focus on solving water balance equations for simulating surface runoff that describes the available catchment water resource (Milly et al. 2005). The land surface and global hydrological models are similar in that they simulate the landscape hydrological processes, run over square grids covering the entire world, and use a priori parameters set to default values or values dependent on climate, vegetation, and soil data layers. The land surface models generally use more process equations and have more parameters. The global hydrological models generally conceptualize the key hydrological processes, have fewer parameters, and also model water use in river systems (some land surface models also simulate irrigation water use). Some of the most widely used land surface models include Global Water Availability Assessment (GWAVA; Meigh et al. 1999), Hydrology-Tiled ECMWF Scheme for Surface Exchanges over Land (HTESSEL; Balsamo et al. 2009), Joint UK Land Environment Simulator (JULES; Best et al. 2011; Clark et al. 2011), Lund-Potsdam-Jena managed Land (LPJmL; Bondeau et al. 2007), Minimal Advanced Treatments of Surface Interaction and Runoff (MATSIRO; Takata et al. 2003), Max Planck Institute-Hydrology Model (MPI-HM; Hagemann and Dumenil 1997), Organizing Carbon and Hydrology in Dynamic Ecosystems (ORCHIDEE; de Rosnay and Polcher 1998), and CSIRO Atmosphere Biosphere Land Exchange (CABLE; Wang et al. 2011). Some of the most widely used global hydrological models include the Hanasaki et al. (2008) model (H08), PCRaster Global Water Balance (PCR-GLOBWB; Wada et al. 2014), Water-Global Assessment and Prognosis (WaterGAP; Alcamo et...