Groundwater Flow : FLAIRS and MODFLOW      
 

Based on the same initial data, the FLAIRS module can be used to calculate groundwater flow using the finite element method while MODFLOW can be used when the finite difference method is prefered. Both FLAIRS en MODFLOW calculate steady state and transient groundwater flow for multi-layered systems. They also allow anisotropy to be accounted for in all layers.

Coupling with other models

triwaco offers an open structure for easy linkage between different models within or outside the triwaco working environment . For example the interaction between groundwater and individual watercourses (defined as line elements) can easily be linked to the branches of a hydraulic surface water model. This link is defined conceptually and will work for any numerical discretization (FLAIRS and MODFLOW alike).

Advanced features of FLAIRS

In addition to the standard options for simulating groundwater flow several special and advanced options are included in FLAIRS. A selection:

Clustering of wells and watercourses

As in most groundwater models abstraction/injection wells can be defined in a variable manner. As a constant abstraction-/injection rate or as a constant head in the well. An advanced option in FLAIRS is that wells can vertically and horizontally be clustered. The program then divides the total amount of discharge or recharge (defined by the user) between the layers in the model in which active and/or horizontally by the clustered wells. The same can be done for line-elements (tubes, faults and watercourses).

Horizontal Boring
A HOrizontal BOring (HOBO) or a range of small wells can be schematised as a single or multiple line-element in an aquifer. A HOBO is a line element representing the wells in a section. For each line element an abstraction rate can be defined. The model will calculate the water level for that particular section at the given abstraction rate. Clustering is again also possible, whereby the same waterlevel is assumed for the clustered watercourses and a total discharge is defined by the user.

Variable Density

In addition to the standard FLAIRS module a separate module has been developed to account for variations in groundwater density. This variable density version, FLAIRSVD, has the same options and possibilities when calculating groundwater flow as the standard version.
 
  Conceptual coupling of watercourses in a groundwater model with the branches of a surface water model
  Simulation of an artificial recharge and recovery scheme. Application of clustered wells (recovery) in combination with clustered watercourses (recharge)