Transmissivity From Distance Drawdown Graphs Calculator

Transmissivity Formula:

\[ T = \frac{2.3 \times q}{2 \times \pi \times \Delta s_D} \]

Transmissivity (T):

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1. What is Transmissivity From Distance Drawdown Graphs?

Transmissivity from distance drawdown graphs is a method to estimate the transmissivity of an aquifer by analyzing the drawdown data from pumping tests. It provides a quantitative measure of how easily water can move through the aquifer material.

2. How Does the Calculator Work?

The calculator uses the transmissivity formula:

\[ T = \frac{2.3 \times q}{2 \times \pi \times \Delta s_D} \]

Where:

\( T \) — Transmissivity (m²/s)
\( q \) — Pumping rate (m³/s)
\( \pi \) — Mathematical constant pi (approximately 3.1416)
\( \Delta s_D \) — Drawdown across log cycle (m)

Explanation: The formula calculates the transmissivity by relating the pumping rate and the drawdown observed across one log cycle on a distance-drawdown graph.

3. Importance of Transmissivity Calculation

Details: Accurate transmissivity estimation is crucial for groundwater resource management, well design, contaminant transport studies, and predicting aquifer response to pumping.

4. Using the Calculator

Tips: Enter pumping rate in m³/s and drawdown across log cycle in meters. Both values must be positive numbers greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: What is transmissivity in hydrogeology?
A: Transmissivity is the rate at which groundwater flows horizontally through an aquifer, representing the ability of the aquifer to transmit water.

Q2: How is drawdown across log cycle determined?
A: It is determined from the slope of the straight-line portion of a distance-drawdown graph plotted on semi-log paper.

Q3: What are typical transmissivity values for different aquifers?
A: Transmissivity values range from 0.001 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 isotropic media, and fully penetrating wells. Results may need adjustment for real-world complexities.

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