Confined Aquifer Discharge with Base 10 given Drawdown at Well Calculator

Formula Used:

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

Coefficient of Permeability (KWH):

m/s

Aquifer Thickness (bw):

Total Drawdown (Stw):

Radius of Influence (Rw):

Radius of Well (r):

Discharge (Q):

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1. What is the Confined Aquifer Discharge Formula?

The Confined Aquifer Discharge formula calculates the rate of groundwater flow from a confined aquifer using the base 10 logarithmic relationship between radius of influence and well radius, incorporating permeability coefficient, aquifer thickness, and drawdown.

2. How Does the Calculator Work?

The calculator uses the discharge formula:

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

Where:

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

Explanation: The formula calculates groundwater discharge from a confined aquifer based on the logarithmic relationship between the radius of influence and well radius, incorporating aquifer properties and drawdown.

3. Importance of Discharge Calculation

Details: Accurate discharge calculation is crucial for groundwater resource management, well design, aquifer testing, and sustainable water extraction planning in confined aquifer systems.

4. Using the Calculator

Tips: Enter all values in appropriate units (meters and m/s). Ensure Radius of Influence is greater than Radius of Well. All values must be positive and valid for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is a confined aquifer?
A: A confined aquifer is an aquifer bounded above and below by impermeable layers, where groundwater is under pressure greater than atmospheric pressure.

Q2: Why use base 10 logarithm in this formula?
A: The base 10 logarithm is used for convenience in calculations and is commonly employed in well hydraulics equations for confined aquifers.

Q3: What is radius of influence?
A: Radius of influence is the distance from the well center to the point where drawdown becomes negligible and the water table remains unaffected.

Q4: How does aquifer thickness affect discharge?
A: Greater aquifer thickness allows for higher discharge rates as there is more water-bearing material available for extraction.

Q5: What are typical values for coefficient of permeability?
A: Permeability coefficients range from 10⁻² m/s for gravel to 10⁻⁹ m/s for clay, with sand typically around 10⁻⁴ to 10⁻⁵ m/s.