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Lecture 7 & 8. Refraction of q Equivalent K for fractured media. Refraction of q. Flow across boundary is equal Pressure at interface is the same in both PMs. Example.
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Lecture 7 & 8 Refraction of q Equivalent K for fractured media
Refraction of q Flow across boundary is equal Pressure at interface is the same in both PMs
Example Downward seepage occurs from a shallow pond to a water table. A conservative traces is introduced at point A. Calculate the location of tracer appearance at the water table and the time it takes. Neglect dispersion, diffusion and assume subsurface fully saturated.
K for fractured PMsection 2.2.4 text Example 2.2.2 Fracture thickness = 0.01 cm Fracture spacing = 220 cm Q (total) = Q (pm) + Q (fracture) Keff b I = K b I + V H 1 K eff = K + V H/b K `
Storage in unconfined aquifers & 1-D flow equation
Moisture distribution & water retention curve Capillary rise Soil representation by a bundle of capillary tubes Water retention curve BC model VG model Specific yield
Flow equation Assume horizontal flow h does not depend on z Horizontal aquifer base Mass balance ROMA= net mass flux in
W Qx+Δx Qx H(x) Δx x Mass balance ROMA= net mass flux in
Flow Equation continued Using DL in mass balance and assuming steady flow we get Solving we get
Applications • Flow through embankment (example 2.3.1) • Agricultural drains (example 2.3.2)
2-d flow in unconfined aquifers Continuity Use darcy’s law in continuity to get or
For steady homogeneous case Or using Laplacian operator
Radial flow In axisymmetric problems the Laplacian operator becomes Solving the GDE we get
Example 2.3.3 txt Consider a pumping well in an unconfined aquifer receiving a recharge at a rate W. The saturated thickness beyond the radius of influence of the well (R) is H0 examine drawdown distribution and value of R.