Drawdown At Well Given Coefficient Of Transmissibility Calculator

Formula Used:

\[ s_t = \frac{Q}{\frac{2\pi T}{\ln\left(\frac{R_w}{r}\right)}} \]

Discharge (Q):

m³/s

Coefficient of Transmissibility (T):

m²/s

Radius of Influence (R_w):

Radius of Well (r):

Total Drawdown in Well (s_t):

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1. What is the Drawdown at Well Formula?

The drawdown at well formula calculates the reduction in hydraulic head observed at a well in an aquifer, typically due to pumping. It's based on the coefficient of transmissibility and other hydrogeological parameters.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ s_t = \frac{Q}{\frac{2\pi T}{\ln\left(\frac{R_w}{r}\right)}} \]

Where:

\( s_t \) — Total drawdown in well (m)
\( Q \) — Discharge rate (m³/s)
\( T \) — Coefficient of transmissibility (m²/s)
\( R_w \) — Radius of influence (m)
\( r \) — Radius of well (m)
\( \pi \) — Archimedes' constant (3.14159)
\( \ln \) — Natural logarithm function

Explanation: The formula calculates the drawdown based on the pumping rate, aquifer transmissibility, and geometric properties of the well system.

3. Importance of Drawdown Calculation

Details: Accurate drawdown calculation is crucial for well design, determining safe yield of aquifers, assessing environmental impacts of groundwater extraction, and managing water resources sustainably.

4. Using the Calculator

Tips: Enter discharge in m³/s, coefficient of transmissibility in m²/s, and both radii in meters. All values must be positive and the radius of influence should be greater than the well radius for valid results.

5. Frequently Asked Questions (FAQ)

Q1: What is coefficient of transmissibility?
A: 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 typically measured from pumping tests and represents the distance from the well where drawdown becomes negligible.

Q3: What factors affect drawdown in a well?
A: Drawdown is affected by pumping rate, aquifer properties, well construction, and duration of pumping.

Q4: When is this formula most accurate?
A: This formula works best for confined aquifers with homogeneous properties and steady-state conditions.

Q5: What are typical units for these parameters?
A: Discharge in m³/s, transmissibility in m²/s, and distances in meters are standard SI units used in hydrogeology.