Water in soil and Darcy's law

What this module covers

• Define elevation, pressure and total head, and explain why flow follows total head
• State and apply Darcy's law for velocity and flow rate
• Distinguish the Darcy velocity from the true seepage velocity
• Compute the equivalent permeability of layered soils, parallel and normal to the layers
• Explain what a constant-head and a falling-head test measure

Lessons

1. 7.1

   Heads and hydraulic gradient

   Water flows from high total head to low — not from high pressure to low.

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2. 7.2

   Darcy's law and seepage velocity

   The linear law for flow through soil, and why the water moves faster than it looks.

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3. 7.3

   Layered soils and permeability tests

   Flow along the layers versus across them, and how k is measured.

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