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Types of aquifer with diagram

Short answer

Unconfined aquifers have a free water table at atmospheric pressure; confined aquifers are between impermeable beds with water under pressure; semi-confined aquifers leak through aquitards; perched aquifers form above local impermeable lenses. Intergranular, fractured, and karst aquifers are also recognized.

Describe the types of aquifer with suitable diagrams.

Aquifers are classified by the position of the water surface and the confining beds.

1. Unconfined (water-table) aquifer

The upper surface is the water table, free to rise and fall with recharge. Water is at atmospheric pressure.

2. Confined (artesian) aquifer

Sandwiched between two impermeable beds. Water is under pressure, so it rises above the aquifer top in wells; if the piezometric level is above ground, wells flow freely (artesian well).

3. Semi-confined (leaky) aquifer

Overlain or underlain by an aquitard through which water leaks slowly.

4. Perched aquifer

A small unconfined water body held above the main water table by a local impermeable lens.

 . . . . . . . . . . . . . . . . . . . . . . . . .  piezometric surface
 _________________________________________________  ground surface
        ~~~~~~~~~ perched water table
        ========= clay lens
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  main water table
    unconfined aquifer (sand, gravel)
 ================= clay (aquiclude) ===============
    confined aquifer (sand), water under pressure
 ================= clay (aquiclude) ===============

Based on rock type, aquifers are also described as intergranular (alluvium), fractured-rock and karst (limestone) aquifers.

✓ Answer checked by Claude Opus 5.5 (high effort)

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