Coefficient Of Permeability Given Confined Aquifer Discharge With Base 10 Calculator

Formula Used:

\[ KWH = \frac{Q}{\frac{2.72 \times bw \times Stw}{\log\left(\frac{Rw}{r}, 10\right)}} \]

Discharge (Q):

m³/s

Aquifer Thickness (bw):

Total Drawdown in Well (Stw):

Radius of Influence (Rw):

Radius of Well (r):

Coefficient of Permeability (KWH):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is the Coefficient of Permeability?

The Coefficient of Permeability in Well Hydraulics describes how easily a liquid will move through the soil. It is a key parameter in groundwater hydrology that quantifies the ability of porous media to transmit fluids.

2. How Does the Calculator Work?

The calculator uses the formula for confined aquifers with base 10 logarithm:

\[ KWH = \frac{Q}{\frac{2.72 \times bw \times Stw}{\log\left(\frac{Rw}{r}, 10\right)}} \]

Where:

\( KWH \) — Coefficient of Permeability (m/s)
\( Q \) — Discharge rate (m³/s)
\( bw \) — Aquifer Thickness (m)
\( Stw \) — Total Drawdown in Well (m)
\( Rw \) — Radius of Influence (m)
\( r \) — Radius of Well (m)

Explanation: This formula calculates the permeability coefficient based on pumping test data from a confined aquifer, using logarithmic transformation of the radial distance ratio.

3. Importance of Permeability Calculation

Details: Accurate permeability estimation is crucial for groundwater resource assessment, well design, contaminant transport modeling, and designing effective dewatering systems for construction projects.

4. Using the Calculator

Tips: Enter all values in consistent units (meters and m³/s). Ensure that radius of influence is greater than radius of well, and all values are positive. Field measurements should be taken under steady-state pumping conditions.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical range of permeability values?
A: Permeability values range from 10⁻¹² m/s for clay to 10⁻¹ m/s for gravel. Most aquifers have values between 10⁻⁵ to 10⁻³ m/s.

Q2: How does this differ from unconfined aquifer calculations?
A: Confined aquifer equations assume constant aquifer thickness, while unconfined aquifer calculations account for the water table drawdown cone and varying saturated thickness.

Q3: What are common sources of error in permeability calculations?
A: Errors can arise from inaccurate measurement of drawdown, improper determination of radius of influence, well construction effects, and non-ideal aquifer conditions.

Q4: When should this equation not be used?
A: This equation assumes homogeneous, isotropic aquifer conditions and steady-state flow. It may not be accurate for fractured rock aquifers, anisotropic conditions, or during transient pumping phases.

Q5: How is radius of influence determined in practice?
A: Radius of influence is typically determined by monitoring observation wells at different distances from the pumping well and identifying where drawdown becomes negligible.