Flux Links to/from Aquifers

The only way to transport mass out of an Aquifer is by specifying an advective mass flux link A mass flux link in which a quantity of a medium is specified to flow from one pathway to another, carrying dissolved, sorbed, and/or suspended species with it. to another pathway. Diffusive mass flux links (diffusive outfluxes), and special purpose mass flux links (direct transfer, precipitate removal and treatment) from Aquifers cannot be created.

Advective mass flux links are used to transport mass via a flowing medium. Mass which is dissolved, or suspended within the flowing medium is transported with the medium as it moves. For Aquifer pathways, the flowing medium is always the Reference Fluid A special type of Fluid element that provides a basis for defining partition coefficients between media for the various species in the model (i.e., the ratio of the species’ concentration in the medium to its concentration in the Reference Fluid at equilibrium)..

Note:If you specify that the flow rate leaving an Aquifer changes suddenly with time, it will change instantaneously throughout the pathway. Although such a response may be appropriate for a confined aquifer system, for a phreatic system, flow changes would not physically propagate instantaneously (the response would be much slower and would propagate as a "wave"). As a result, when changing the flow rate (for a phreatic system) you should be aware of how it will be represented in GoldSim (and generally should only change it slowly). Of course, in most realistic situations, unless you are applying an artificial sudden change (e.g., pumping), flow rates will in fact change slowly (not suddenly).

You can transport mass into an Aquifer via an advective mass flux link An interconnnection between two transport pathways that defines the rate at which species move between the pathways. from any other type of pathway and/or via a diffusive mass flux link from a Cell pathway A transport pathway element that is mathematically equivalent to a finite difference node. Cells are commonly applied to simulate discrete compartments in an environmental system (such as ponds, lakes, shallow soil compartments, or the atmosphere).. Within GoldSim, the concentration and diffusive length on the Aquifer side of a diffusive mass flux link A mass flux link in which species diffuse between pathways according to a concentration gradient. are assumed to be zero. Hence, like advective mass flux links, diffusive mass flux links involving Aquifers are uni-directional.

Warning: GoldSim does not enforce a balance for the flow of the Reference Fluid in an Aquifer. That is, the Inflows into an Aquifer do not need to be equal to the Outflows from the Aquifer. If the specified Outflows are greater than the specified Inflows, conceptually the effect on the species The chemical (or non-chemical, such as bacterial or viral) constituents that are stored and transported through an environmental system in a contaminant transport model. In GoldSim, the Species element defines all of the contaminant species being simulated (and their properties). concentrations leaving the Aquifer is one of dilution, since "clean" fluid is assumed to be flowing into the Aquifer. If, however, the specified Outflows are less than the specified Inflows, in the absence of decay and dispersion, the species concentrations leaving the Aquifer would be greater than those entering the Aquifer. Conceptually, GoldSim would assume that a quantity of "clean" fluid (carrying no species mass) flowed out of the Aquifer in order to conserve the flow rate and volume in the Aquifer. Although there are some physical situations in which you may actually want to do this (e.g., in order to simulate the evaporation of Water from an Aquifer), typically such behavior would not be intended. As a result, whenever the Inflows to an Aquifer exceed the Outflows, GoldSim provides a (non-fatal) warning message to the Run Log.