Aquifer Thickness from Impermeable Layer given Discharge in Confined Aquifer with Base 10 Calculator

Formula Used:

\[ \text{Initial Aquifer Thickness} = \text{Depth of Water} + \frac{\text{Discharge} \times \log\left(\frac{\text{Radius of Influence}}{\text{Radius of well}}\right)}{2.72 \times \text{Coefficient of Permeability} \times \text{Aquifer Thickness}} \] \[ H_i = h_w + \frac{Q \times \log\left(\frac{R_w}{r}\right)}{2.72 \times K_w \times b_w} \]

Depth of Water (h_w):

Discharge (Q):

m³/s

Radius of Influence (R_w):

Radius of well (r):

Coefficient of Permeability (K_w):

m/s

Aquifer Thickness (b_w):

Initial Aquifer Thickness (H_i):

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1. What is Aquifer Thickness from Impermeable Layer?

The Aquifer Thickness from Impermeable Layer calculation determines the initial thickness of an aquifer above an impermeable layer, considering discharge rates and aquifer properties. This is crucial for understanding groundwater flow and well performance in confined aquifers.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ H_i = h_w + \frac{Q \times \log\left(\frac{R_w}{r}\right)}{2.72 \times K_w \times b_w} \]

Where:

\( H_i \) — Initial Aquifer Thickness (m)
\( h_w \) — Depth of Water above impermeable layer (m)
\( Q \) — Discharge rate (m³/s)
\( R_w \) — Radius of Influence (m)
\( r \) — Radius of well (m)
\( K_w \) — Coefficient of Permeability (m/s)
\( b_w \) — Aquifer Thickness (m)

Explanation: The formula calculates the initial aquifer thickness by adding the water depth to the additional thickness component derived from discharge, permeability, and geometric factors.

3. Importance of Aquifer Thickness Calculation

Details: Accurate aquifer thickness estimation is essential for groundwater resource assessment, well design, pumping test analysis, and predicting aquifer response to extraction.

4. Using the Calculator

Tips: Enter all values in appropriate units (meters for lengths, m³/s for discharge). Ensure all values are positive and radius of influence is greater than well radius for valid results.

5. Frequently Asked Questions (FAQ)

Q1: What is a confined aquifer?
A: A confined aquifer is bounded above and below by impermeable layers, creating pressure conditions that affect water flow.

Q2: Why use base 10 logarithm in this formula?
A: Base 10 logarithms are commonly used in hydrogeological equations as they provide convenient scaling for the large ranges of values encountered.

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

Q4: How does coefficient of permeability affect the result?
A: Higher permeability reduces the additional thickness component, as water flows more easily through the aquifer material.

Q5: When is this calculation most applicable?
A: This calculation is particularly useful for steady-state flow conditions in confined aquifers with known boundary conditions.