Thickness Of Confined Aquifer Given Discharge In Confined Aquifer Calculator

Formula Used:

\[ b_p = \frac{Q}{\frac{2 \pi K_w (H_i - h_w)}{\ln\left(\frac{R_w}{r}\right)}} \]

Discharge (Q):

m³/s

Coefficient of Permeability (K_w):

m/s

Initial Aquifer Thickness (H_i):

Depth of Water (h_w):

Radius of Influence (R_w):

Radius of well (r):

Aquifer Thickness During Pumping (b_p):

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1. What is Aquifer Thickness During Pumping?

Aquifer Thickness During Pumping refers to the thickness of a confined aquifer during the pumping stage. It is an important parameter in hydrogeology that helps determine the aquifer's capacity to yield water under pumping conditions.

2. How Does the Calculator Work?

The calculator uses the formula for confined aquifers:

\[ b_p = \frac{Q}{\frac{2 \pi K_w (H_i - h_w)}{\ln\left(\frac{R_w}{r}\right)}} \]

Where:

\( b_p \) — Aquifer thickness during pumping (m)
\( Q \) — Discharge rate (m³/s)
\( K_w \) — Coefficient of permeability (m/s)
\( H_i \) — Initial aquifer thickness (m)
\( h_w \) — Depth of water in the well (m)
\( R_w \) — Radius of influence (m)
\( r \) — Radius of well (m)
\( \pi \) — Mathematical constant pi (≈3.1416)
\( \ln \) — Natural logarithm function

Explanation: This formula calculates the aquifer thickness during pumping based on the discharge rate, permeability characteristics, and geometric parameters of the well and aquifer system.

3. Importance of Aquifer Thickness Calculation

Details: Accurate calculation of aquifer thickness during pumping is crucial for designing efficient well systems, predicting drawdown effects, managing groundwater resources, and assessing the sustainable yield of confined aquifers.

4. Using the Calculator

Tips: Enter all values in appropriate units (meters for lengths, m³/s for discharge, m/s for permeability). Ensure that radius of influence is greater than well radius, and initial aquifer thickness is greater than water depth for valid calculations.

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 (aquitards or aquicludes) that prevent water from easily entering or leaving the aquifer.

Q2: How does pumping affect aquifer thickness?
A: Pumping causes drawdown which reduces the effective thickness of the aquifer in the vicinity of the well, affecting the aquifer's storage and transmission capabilities.

Q3: What is the radius of influence?
A: The radius of influence is the distance from the center of the well to the point where the drawdown curve meets the original (pre-pumping) water table or potentiometric surface.

Q4: Why is natural logarithm used in the formula?
A: The natural logarithm is used because the flow to a well in a confined aquifer follows a logarithmic drawdown pattern, derived from the Theis equation for radial flow to a well.

Q5: What are typical values for coefficient of permeability?
A: Permeability coefficients vary widely: clay (10⁻⁹-10⁻⁷ m/s), sand (10⁻⁵-10⁻³ m/s), gravel (10⁻³-10⁻¹ m/s). The specific value depends on the aquifer material.