Groundwater flow
The model calculates pore velocity from hydraulic conductivity,
hydraulic gradient, and effective porosity. Pumping changes
hydraulic head and bends the flow field toward the municipal well.
Recharge
Recharge changes hydraulic head, contaminant leaching, and
dilution. A storm pulse can mobilize more contaminant while also
increasing the amount of groundwater available for dilution.
Confining layers
The shallow and deep aquifers exchange water and contaminant mass
according to aquitard thickness, continuity, fractures, vertical
conductivity, and the head difference between layers.
Transport
Advection carries dissolved contaminant with groundwater.
Longitudinal and transverse dispersion spread the plume.
Nitrate-like and petroleum-like presets add simplified decay,
retardation, and persistence.
Contaminant mass
The “Contaminant mass in aquifers” readout adds together the
contaminant currently stored in both the shallow and deep aquifers.
It does not represent the concentration at a single well or the
amount still waiting at the source. The value can increase while
the source releases contaminant and decrease as contaminant leaves
the model boundary or undergoes simplified decay.
Learning alerts
Teaching modes explain important cause-and-effect events. Mystery
Mode only reports evidence from wells students have sampled, so it
does not reveal the source-location answer.
Well evidence
Each well reports hydraulic head and concentration across its
screened layer. In visible-source modes, live readings update as
the model runs. Clicking a well saves a time-stamped measurement
that remains fixed in the sample history. Nested shallow and deep
wells help reveal vertical differences.
Two views
Map view shows plume direction, capture zones, geologic patterns,
and monitoring-well placement. Cross-section view shows the water
table, aquitard, vertical leakage, and well depths.
Important limitation
This is a conceptual two-layer classroom model, not a site-specific
regulatory or engineering model. It simplifies three-dimensional
geology, chemical reactions, fractures, density effects, and
transient groundwater storage.