Aquifer Thickness from Impermeable Layer given Coefficient of Transmissibility Calculator

Formula Used:

\[ \text{Initial Aquifer Thickness} = \text{Depth of Water} + \frac{\text{Discharge} \times \log\left(\frac{\text{Radius of Influence}}{\text{Radius of well}}, e\right)}{2 \times \pi \times \text{Coefficient of Transmissibility}} \]

Depth of Water (hw):

Discharge (Q):

m³/s

Radius of Influence (Rw):

Radius of Well (r):

Coefficient of Transmissibility (Tw):

m²/s

Initial Aquifer Thickness (Hi):

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1. What is the Aquifer Thickness Formula?

The formula calculates the initial aquifer thickness from the impermeable layer based on the coefficient of transmissibility. It provides an accurate assessment of aquifer characteristics for groundwater studies and well design.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

\( hw \) — Depth of Water in the well measured above the impermeable layer (m)
\( Q \) — Discharge rate of flow (m³/s)
\( Rw \) — Radius of Influence measured from center of well (m)
\( r \) — Radius of well (m)
\( Tw \) — Coefficient of Transmissibility (m²/s)
\( \pi \) — Archimedes' constant (≈3.14159)
\( e \) — Napier's constant (≈2.71828)
\( \log \) — Natural logarithm function

Explanation: The equation accounts for the relationship between discharge, aquifer properties, and geometric parameters to determine the initial aquifer thickness.

3. Importance of Aquifer Thickness Calculation

Details: Accurate aquifer thickness estimation is crucial for groundwater resource assessment, well design, pumping test analysis, and sustainable water management.

4. Using the Calculator

Tips: Enter all values in appropriate units. Depth of Water, Discharge, Radius of Influence, Radius of well, and Coefficient of Transmissibility must be positive values.

5. Frequently Asked Questions (FAQ)

Q1: What is the Coefficient of Transmissibility?
A: The coefficient of transmissibility represents the rate of water flow through a vertical strip of aquifer under unit hydraulic gradient.

Q2: How is Radius of Influence determined?
A: Radius of Influence is measured from the center of the well to the point where the drawdown curve meets the original water table.

Q3: What are typical values for Coefficient of Transmissibility?
A: Values vary widely depending on aquifer material, ranging from 0.1 m²/day for clay to over 1000 m²/day for gravel aquifers.

Q4: When is this formula most applicable?
A: This formula is particularly useful for confined aquifers and steady-state flow conditions around pumping wells.

Q5: What are the limitations of this approach?
A: The formula assumes homogeneous aquifer properties, constant discharge, and idealized boundary conditions that may not fully represent complex field conditions.