The River modules includes specification of River specific features for the project. Options are:
· River modules
- – Rainfall runoff
- – Hydrodynamic
- – Water quality
Rainfall-runoff modelling can be included in the River model.
Inclusion of Rainfall runoff in a simulation requires that one or more Catchments are defined in the River model. Runoff from catchments is calculated from user-defined Catchment characteristics and meteorological data.
Following rainfall-runoff models are available:
· NAM:
A lumped, conceptual rainfall-runoff model, simulating the overland flow, interflow, and baseflow components as a function of the moisture contents in four storages.
· UHM:
The Unit Hydrograph Model includes different loss models (constant, proportional) and the SCS method for estimating storm runoff.
· Time Area:
Runoff simulation based on the Time area method considering losses , size of contributing area as well as concentration time as function of catchment shape. The Time-area model is also known as ‘Urban Runoff Model A’.
· Kinematic Wave:
The Kinematic wave runoff model calculates surface runoff as flow in open channels considering gravitational and friction forces only including various hydrological losses. The Kinematic wave model is also known as ‘Urban Runoff Model B’.
The type of rainfall runoff model and associated, required input data are specified in the Catchment definitions page (cf. Section 7.1.2).
Rainfall runoff results can be used as input for a hydrodynamic simulation. It is possible to either run the two modules simultaneously, or to use a Rainfall runoff result file as input for the hydrodynamic simulation. The latter will reduce the simulation time, and is achieved by enabling the 'Data' but not the 'Simulation' for rainfall runoff.
The Hydrodynamic checkboxes enable editing of River model data and activates the hydrodynamic river model simulations. Hydrodynamic river simulations in MIKE HYDRO River uses the MIKE 1D simulation engine (for details on the MIKE 1D simulation engine, please refer to the MIKE 1D reference manual.
Link to the MIKE 1D manual can be found in the MIKE HYDRO Documentation index).
Advection-Dispersion modelling include simulation of transport and spreading of pollutants as function of the hydrodynamic conditions in the rivers. The Advection-Dispersion module includes a simple decay function but no other water quality processes.
Advection-Dispersion and Hydrodynamic simulations can be performed simultaneously. However, it is also possible to decouple them, by using a Hydrodynamic result file as input for the Advection-Dispersion simulation. This will significantly reduce the simulation time, and is achieved by enabling the 'Data' but not the 'Simulation' for the Hydrodynamic module, while enabling both for the Advection-Dispersion module.
Water quality processes in MIKE HYDRO River is included by use of MIKE ECO Lab, which is a highly flexible framework for defining water quality models. MIKE ECO Lab utilise a concept of templates where water quality models are defined with equations and variables, and the water quality option therefore, allows the usage of different water quality models/templates depending on the issue of concern. MIKE HYDRO Basin installation includes two predefined water quality templates that can be applied as is - or can be adjusted by the user to conform with the specific project requirements.
Sediment transport can be described based on various model types (e.g. van Rijn, Meyer-Peter & Muller, Engelund-Hansen, Engelund-Fredsoe, Yang, or user-defined empirical formulas). Graded or mixed sediment descriptions can be applied by defining a number of different sediment fractions, which are treated separately by the sediment transport module. Sediment transport is computed from hydrodynamic conditions, and dynamic changes in the river morphology can in return affect the hydrodynamic conditions.
Data assimilation module include an updating feature for continuous processing and updating of model states during simulations. Data assimilation is used for many types of applications, but in particular for flood forecasting (or other types of forecasting) where the forecasted values of river state conditions (water levels, flows etc.) is much more accurate and reliable when updating and error estimation is included as part of the forecast simulations.