Physical groundwater flow model

Student excercise: determination of the hydraulic conductivity of the 'groundwater model' (Fig)

• establish a flow from left to right in the model
• put dye into three wells tapping the upper (thick) aquifer and measure the hydraulic head relative to the bench as a function of distance from the recharge area, which is the left boundary of the sand in the box.
• after establishing a continuous flow in the model, let the discharge flow into a (weighted) beaker for approximately 10 minutes. Weigh the beaker afterwards and determine Q. You can also measure the volume directly by using a calibrated cylinder.
• A is the average cross sectional area of the sand perpendicular to the flow of the water, thickness * width
• plot the hydraulic head as a function of distance, and describe the function that you obtain
• calculate k using Darcy's law by using the hydraulic head measurements on both ends of the model
• look at the table of hydraulic conductivities (Fig), what kind of aquifer rock does your measurement indicate and does it make sense?
• what simplifying assumptions are we making here?

• inject some dye into one of the wells tapping the sand on the left side of the model
• while the model is running, determine the velocity at which the plume is moving

use the above formula (n = q/v) to determine the porosity

• inject different dyes into one of the wells on the left into the middle injection well and into the landfil
• recharge and discharge areas, aquifers, pumping wells, artesian well, piezometers, land fill, river,.....
• springs may originate in artesian aquifers
• water table
• wells draw water from all directions
• cone of depression
• drawing water from a well can interfere with the ability of neighboring wells to produce water (they go dry!)
• groundwater is related to surface waters, use the lake as discharge area, by draining it, dye should show the movement of water; after closing the drain, lake should fill up again
• relation between confined and unconfined aquifers: pumping on one aquifer has not a big effect on the other one
• however, there is water moving through the confining bed
• texture of material affects flow rate: gravel has higer conductivity almost confined conditions, water should move upward! Also other plumes in sand should spread more slowly
• inhomogeneities in the aquifers affect flow