MOHID Land
MOHID Land is the hydrology module within the three-dimensional MOHID Water Modelling System. MOHID is an integrated system for water flow, consisting of three main modules: Water for three-dimensional fluid dynamics, Land for hydrology and Soil for groundwater flow. The MOHID Land module is a watershed mathematical model — or hydrological transport model — designed to simulate the flow of water in a drainage basin and aquifer. The interactions between the different processes (like water exchange between aquifer and river) are calculated dynamically by the model, using the hydraulic gradients. The different processes occurring in a basin are programmed in different modules. The user can choose which modules to activate, allowing simulation of the desired ones only.
MOHID Land was developed within the framework of three EU-funded projects: EcoRiver,[1] TempQsim[2] and ICReW[3] for the simulation of water flow in watersheds with pathways for river and groundwater flow. The porous media module was developed in close collaboration with soil scientists from EAN-INIA (Portuguese National Agronomic Station). Between 2009 and 2011 ESA financed Aquapath-Soil[4] project to apply MOHID Land to support irrigation using Satellite LAI as input to the model, obtaining maps of Actual Evapotranspiration. Latter, through FIGARO[5] project, a simillar aplications was made but at european level using AQUASAFE[6] as the engine that joined models and data to produce forecasts on irrigation.
Main processes solved[edit]
- Drainage network (kinematic wave equation);
- 2D overland flow (kinematic wave equation);
- Infiltration calculated by Richards equation or Green–Ampt approach;
- Soil redistribution by Richards equation;
- Aquifer flow by Darcy's law;
- Evapotranspiration is calculated with the 'FAO crop reference evapotranspiration', a standardized Penman–Monteith equation.[7]
Dynamical time step adaptation[edit]
MOHID Land uses an adaptive time-stepping method in its main hydrodynamic cycle. Within an iterative cycle, if the water volume — of reach or overland flow or porous media — varies more than a user defined percentage during two consecutive time steps, the model automatically decreases the time step. Thereafter the model recalculates the current solution with a smaller time step for the affected process (reach or overland flow or porous media). This process is repeated until the volume variation is less than the user defined value mentioned above. The time step dynamically increases again when the model verifies that flow is “stable”. For example within the module "Drainage Network" the time step may be reduced to very short intervals during flush events. This procedure avoids the occurrence of negative volumes and optimizes the time it takes to make a certain simulation, without compromising model stability. Time steps of the processes — computed in the different sub-models — can be chosen differently, adding more to the optimization of the computational cost.
GIS model interfaces[edit]
You can download interfaces to prepare inputs and to analyse model results. Presently available two options:
- a completely free interface from MOHID website MOHID Official Webpage.
- the new graphic interface can be downloaded from Action modulers.
Notes[edit]
References[edit]
- Official website
- Ramiro Neves; et al. (2008), Sustainable Use and Development of Watersheds, retrieved 2008-10-02
- Pedro Bagulho Galvão; Ramiro Neves; Adelio Silva; Pedro Chambel Leitão; Frank Braunchweig (2003), "Integrated watershed modeling" (PDF), ESA Meris Workshop, Frascati, Italy, retrieved 2008-10-30
- Rosa Trancoso; Frank Braunchweig; Pedro Chambel Leitão; Mathias Obermann; Ramiro Neves (2009), "An advanced modelling tool for simulating complex river systems", Science of The Total Environment, retrieved 2009-03-20
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