Coefficient Of Permeability When Equilibrium Equation For Well In Unconfined Aquifer Calculator

Formula Used:

\[ K = \frac{Q_u}{\pi \frac{(H_2^2 - H_1^2)}{\ln\left(\frac{r_2}{r_1}\right)}} \]

Steady Flow of an Unconfined Aquifer (Qu):

m³/s

Water Table Depth 2 (H2):

Water Table Depth (H1):

Radial Distance at Observation Well 2 (r2):

Radial Distance at Observation Well 1 (r1):

Coefficient of Permeability (K):

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1. What is the Coefficient of Permeability?

The Coefficient of Permeability of soil describes how easily a liquid will move through the soil. It is a key parameter in hydrogeology and civil engineering for understanding groundwater flow and designing drainage systems.

2. How Does the Calculator Work?

The calculator uses the equilibrium equation for well in unconfined aquifer:

\[ K = \frac{Q_u}{\pi \frac{(H_2^2 - H_1^2)}{\ln\left(\frac{r_2}{r_1}\right)}} \]

Where:

\( K \) — Coefficient of Permeability (m/s)
\( Q_u \) — Steady Flow of an Unconfined Aquifer (m³/s)
\( H_2 \) — Water Table Depth 2 (m)
\( H_1 \) — Water Table Depth (m)
\( r_2 \) — Radial Distance at Observation Well 2 (m)
\( r_1 \) — Radial Distance at Observation Well 1 (m)
\( \pi \) — Archimedes' constant (approximately 3.1416)
\( \ln \) — Natural logarithm function

Explanation: This equation calculates the permeability coefficient based on steady-state flow conditions in an unconfined aquifer with observation well data.

3. Importance of Permeability Calculation

Details: Accurate permeability calculation is crucial for groundwater resource management, contaminant transport studies, foundation design, and environmental impact assessments.

4. Using the Calculator

Tips: Enter all values in appropriate units (meters for distances, m³/s for flow rate). Ensure radial distances are different (r2 ≠ r1) and all values are positive.

5. Frequently Asked Questions (FAQ)

Q1: What is an unconfined aquifer?
A: An unconfined aquifer is a groundwater aquifer where the water table is exposed to the atmosphere through pore spaces in the overlying material.

Q2: Why are two observation wells needed?
A: Two observation wells at different radial distances are required to establish the hydraulic gradient and calculate the permeability coefficient accurately.

Q3: What are typical values for permeability coefficient?
A: Permeability values range from 10⁻¹² m/s for clay to 10⁻¹ m/s for gravel, depending on soil type and composition.

Q4: What assumptions does this equation make?
A: The equation assumes steady-state flow, homogeneous and isotropic aquifer, and that the Dupuit-Forchheimer assumptions apply.

Q5: When is this equation not applicable?
A: This equation may not be accurate for confined aquifers, anisotropic conditions, or when significant vertical flow components are present.