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Groundwater and contaminant transport

Let's look at the movement of contamination in groundwater by changing the location of the well and the contamination source, pumping amount, and hydraulic conductivity.

    E19 · Groundwater and contaminant transportReady
    You can also experiment with the numbers and controls below the scene.

    Earth Science · Ocean · Climate · Water Cycle / Principles and Exploration

    Groundwater and contaminant transport — principles and investigation

    Groundwater does not flow all at once in the same direction, but flows according to differences in water head. Compare the flow lines by changing the hydraulic conductivity, well pumping amount, pollutant source, and the location of the well. If a well alters the surrounding flow, the path of contaminants may also change.

    How does it work?

    The water flows toward the lower head and gathers around the well. The arrival time of contamination varies depending on the flow rate, location, diffusion, and pumping conditions.

    Key relationship

    q=−K∇h · v=q/n · n=0.25

    Try this investigation

    1. First, calculate the steady-state head repeatedly and then move 100 kg of contamination. Look at the background color, dorsal head line, arrow and red pollution cloud. A sound will be heard when more than 0.01 kg reaches the well compartment.
    2. At the same location and pumping amount, run K=10 and 5 m/day and record the distribution/model arrival time of 300 days.
    3. Maintain K=10 and only change the pumping amount or the vertical position of the well. Compare the overall mass balance including boundary outflow and amniotic fluid removal.

    Interpreting your results

    What if K=10 m/day, head gradient magnitude 0.01, and n=0.25?

    The size of the flow velocity is K × slope = 0.1 m/day and the actual flow velocity is q/n = 0.4 m/day. The time for uniform straight flow is distance/speed.

    Assumptions and limitations

    40×20 grid, spacing 5 m, thickness 1 m, uniform K·porosity n=0.25·diffusion coefficient 0.2 m²/day. The left and right fixed heads are 11.95/10 m, and the top and bottom are impermeable boundaries. The steady flow head is repeated up to 12 times per time, a total of 1800 times, or a change of 1e-8 m. Calculate wind advection and conservative diffusion by dividing the settling time. The arrival time is a model value based on 0.01 kg of well space and is not an observational prediction. Reaction, adsorption, and heterogeneous layers are excluded.