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Lecture 7

Lecture 7. 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

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  1. Lecture 7 Refraction of q Equivalent K for fractured media

  2. Refraction of q Flow across boundary is equal Pressure at interface is the same in both PMs

  3. 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.

  4. 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 `

  5. Storage in unconfined aquifers & 1-D flow equation

  6. Moisture distribution & water retention curve Capillary rise Soil representation by a bundle of capillary tubes Water retention curve BC model VG model Specific yield

  7. Flow equation Assume horizontal flow h does not depend on z Horizontal aquifer base Mass balance ROMA= net mass flux in

  8. W qx+Δx qx H(x) Δx x Mass balance ROMA= net mass flux in

  9. Flow Equation continued Using DL in mass balance and assuming steady flow we get Solving we get

  10. Applications • Flow through embankment (example 2.3.1) • Agricultural drains (example 2.3.2)

  11. 2-d flow in unconfined aquifers Continuity Use darcy’s law in continuity to get or

  12. For steady homogeneous case Or using Laplacian operator

  13. Radial flow In axisymmetric problems the Laplacian operator becomes Solving the GDE we get

  14. 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.

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