Hydrogeology terminology – what is an aquiclude? In groundwater engineering, identify the most accurate definition of an aquiclude from the choices below. Your answer should reflect standard usage in civil and environmental engineering.

Introduction / Context:
An understanding of subsurface units—aquifers, aquitards, and aquicludes—is fundamental for groundwater exploration, well design, and pollution control. Mislabeling these units can lead to wrong inferences about yield and contaminant migration.

Given Data / Assumptions:

• Standard hydrogeologic definitions are used.
• Flow through the geologic unit described as an aquiclude is negligible for engineering purposes.
• Adjacent water-bearing units are termed aquifers.

Concept / Approach:
An aquifer transmits water readily; an aquitard transmits water slowly; an aquiclude is effectively impermeable (transmission ~ zero) but may still contain water. Aquicludes commonly act as confining beds between two aquifers and control vertical leakage and artesian conditions.

Step-by-Step Solution:
Identify the keyword “aquiclude” → unit of very low permeability (nearly impervious).Relate to its position → typically lies between aquifers and acts as a confining bed.Select the option explicitly describing a confined, impervious bed between aquifers.

Verification / Alternative check:
Groundwater texts define aquiclude as a formation that can store water but does not transmit it appreciably; it serves as a confining layer creating artesian conditions in adjacent aquifers.

Why Other Options Are Wrong:

• (a) and (b) describe aquifers (unconfined and confined) that do transmit water.
• (d) is vague and ignores permeability.
• (e) is incorrect because a precise definition is provided in (c).

Common Pitfalls:
Confusing aquiclude with aquitard; the latter transmits slowly but not negligibly. Also, assuming an aquiclude is dry—many are saturated but non-transmitting.

Final Answer:
A confined bed of essentially impervious material situated between aquifers