---
title: "Short note: Aquiclude"
subject: "Engineering Geology II"
chapter: 3
key: "semester_4/engineering_geology_ii:short-note-aquiclude"
source: https://www.bctengineer.com/q/semester_4/engineering_geology_ii/short-note-aquiclude
site: BCT Engineering
---

# Short note: Aquiclude

Engineering Geology II · Chapter 3: Hydrogeology

- Asked in: 2080 Chaitra, 2 marks
- Video: [Geological Formations | AQUIFER AQUITARD AQUICLUDE AQUIFUGE](https://www.youtube.com/watch?v=YvIxNHt8Dkc) — Bangloo Engineers
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_4/engineering_geology_ii/short-note-aquiclude
- Whole chapter: https://www.bctengineer.com/md/semester_4/engineering_geology_ii/chapter-3

## Question

Write a short note on aquiclude.

## Short answer

An aquiclude is a saturated but impermeable geological formation (e.g. clay) that contains water but cannot transmit it to wells. It forms confining layers for artesian aquifers, acts as a leakage barrier, and is used in dam cores, yet may induce perched water tables and slope problems.

## Answer

An **aquiclude** is a saturated geological formation that contains water but is so impermeable that it cannot transmit it in useful quantity to wells or springs.

- Typical examples are clay and unfractured shale. Clay may have high porosity (40-60%) but very low hydraulic conductivity ($K<10^{-9}$ m/s).
- It forms the upper and lower boundary of **confined (artesian) aquifers**, so water stays under pressure.
- Acts as a natural barrier against contamination and vertical movement of water.
- Differs from an **aquitard** (low permeability, but transmits water slowly) and an **aquifuge** (neither contains nor transmits water).

#### Engineering importance
- Good as foundation of reservoirs and ponds, since it prevents leakage.
- Clay is used as impervious core in earth dams.
- Perched water tables form over aquicludes and can cause landslides and slope instability.
- Clay aquicludes can form weak, compressible foundations and may swell.

## Check yourself

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

1. What is an aquiclude?
   A. A formation that transmits water freely to wells
   B. A formation that neither contains nor transmits water
   C. A saturated formation that contains water but cannot transmit it in useful quantity
   D. An unsaturated gravel layer
   Answer: C. Clay is an example: high porosity but very low hydraulic conductivity. (Key point: Aquiclude definition)

2. Which pairing is correct?
   A. Aquitard transmits freely; aquifuge contains water
   B. Aquifuge transmits slowly; aquitard contains no water
   C. All three are good aquifers
   D. Aquitard transmits slowly; aquifuge neither contains nor transmits water
   Answer: D. An aquitard is leaky and slow, while an aquifuge is totally impervious and dry. (Key point: Aquiclude vs aquitard vs aquifuge)

3. What is the role of aquicludes in a confined aquifer?
   A. They form the upper and lower boundaries so the water stays under pressure
   B. They supply the water to wells
   C. They increase recharge
   D. They dissolve to form caves
   Answer: A. Impermeable bounding layers confine the aquifer and keep it pressurised. (Key point: Role in confined aquifers)