---
title: "Types of aquifer with diagram"
subject: "Engineering Geology II"
chapter: 3
key: "semester_4/engineering_geology_ii:aquifer-types-diagram"
source: https://www.bctengineer.com/q/semester_4/engineering_geology_ii/aquifer-types-diagram
site: BCT Engineering
---

# Types of aquifer with diagram

Engineering Geology II · Chapter 3: Hydrogeology

- Asked in: 2077 Chaitra, 2 marks; 2070 Bhadra, 2 marks (asked 2 times)
- Video: [Types of Aquifers](https://www.youtube.com/watch?v=N3w2lr5MpR4) — Earth Explained
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_4/engineering_geology_ii/aquifer-types-diagram
- Whole chapter: https://www.bctengineer.com/md/semester_4/engineering_geology_ii/chapter-3

## Question

Describe the types of aquifer with suitable diagrams.

## 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.

## Answer

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.

```text
 . . . . . . . . . . . . . . . . . . . . . . . . .  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.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is the upper surface of an unconfined aquifer?
   A. A confining clay layer
   B. The water table at atmospheric pressure
   C. The piezometric surface
   D. The ground
   Answer: B. The water table is a free surface that rises and falls with recharge. (Key point: Unconfined)

2. When does a well flow freely in a confined aquifer?
   A. Piezometric level above ground level
   B. Water table below ground
   C. The aquifer is dry
   D. The well is shallow
   Answer: A. If the piezometric level is above ground, pressure pushes water out as a flowing artesian well. (Key point: Artesian well)

3. What characterises a semi-confined (leaky) aquifer?
   A. Aquitard above or below through which water leaks slowly
   B. No confining beds
   C. Karst caves
   D. Perched lens only
   Answer: A. An aquitard allows slow leakage into or out of the aquifer. (Key point: Semi-confined)

## Related in Engineering Geology II

- [Confined versus unconfined aquifer](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Aconfined-unconfined-aquifer) — Engineering Geology II, chapter 3, asked 4×

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