Transmissivity Derived From Time Drawdown Graphs Calculator

Transmissivity Formula:

\[ \tau = \frac{2.3 \times q}{4 \times \pi \times \Delta s} \]

Transmissivity (τ):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is Transmissivity?

Transmissivity refers to the measure of how much water can be transmitted horizontally through an aquifer. It is the product of the hydraulic conductivity of the aquifer and its saturated thickness.

2. How Does the Calculator Work?

The calculator uses the transmissivity formula:

\[ \tau = \frac{2.3 \times q}{4 \times \pi \times \Delta s} \]

Where:

\( \tau \) — Transmissivity (m²/s)
\( q \) — Pumping Rate (m³/s)
\( \Delta s \) — Drawdown Across One Log Cycle (m)
\( \pi \) — Archimedes' constant (approximately 3.1416)

Explanation: This formula calculates the transmissivity of an aquifer based on pumping test data and drawdown measurements across one log cycle.

3. Importance of Transmissivity Calculation

Details: Accurate transmissivity estimation is crucial for groundwater resource assessment, well design, contaminant transport modeling, and sustainable aquifer management.

4. Using the Calculator

Tips: Enter pumping rate in cubic meters per second and drawdown across one log cycle in meters. All values must be valid (greater than 0).

5. Frequently Asked Questions (FAQ)

Q1: What is the significance of the 2.3 factor in the formula?
A: The 2.3 factor comes from the conversion between natural logarithms and base-10 logarithms (ln(10) ≈ 2.3026).

Q2: How is drawdown across one log cycle determined?
A: Drawdown across one log cycle is determined from time-drawdown graphs by measuring the vertical distance between drawdown values that are one log cycle apart.

Q3: What are typical transmissivity values for different aquifers?
A: Transmissivity values range from less than 1 m²/day for clay aquitards to over 1000 m²/day for highly productive sand and gravel aquifers.

Q4: What are the limitations of this method?
A: This method assumes ideal aquifer conditions, homogeneous properties, and fully penetrating wells. Results may need adjustment for boundary conditions or aquifer heterogeneity.

Q5: How does transmissivity relate to hydraulic conductivity?
A: Transmissivity equals hydraulic conductivity multiplied by the saturated thickness of the aquifer (T = K × b).