Transmissivity When Discharge at Edge of Zone of Influence Calculator

Formula Used:

\[ T_{iz} = \frac{Q_{sf} \cdot \ln\left(\frac{r_2}{r_1}\right)}{2 \pi s'} \]

Steady Flow in a Confined Aquifer (Qsf):

m³/s

Radial Distance at Observation Well 2 (r2):

Radial Distance at Observation Well 1 (r1):

Possible Drawdown in Confined Aquifer (s'):

Transmissivity at Edge of Zone of Influence (Tiz):

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1. What is Transmissivity at Edge of Zone of Influence?

Transmissivity at Edge of Zone of Influence is the capacity of the aquifer to transmit water at the boundary of the area influenced by the pumping well. It represents the hydraulic conductivity multiplied by the saturated thickness of the aquifer.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ T_{iz} = \frac{Q_{sf} \cdot \ln\left(\frac{r_2}{r_1}\right)}{2 \pi s'} \]

Where:

\( T_{iz} \) — Transmissivity at Edge of Zone of Influence (m²/s)
\( Q_{sf} \) — Steady Flow in a Confined Aquifer (m³/s)
\( r_2 \) — Radial Distance at Observation Well 2 (m)
\( r_1 \) — Radial Distance at Observation Well 1 (m)
\( s' \) — Possible Drawdown in Confined Aquifer (m)
\( \pi \) — Archimedes' constant (≈3.14159)
\( \ln \) — Natural logarithm function

Explanation: This formula calculates the transmissivity based on steady flow conditions in a confined aquifer using drawdown measurements from two observation wells.

3. Importance of Transmissivity Calculation

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

4. Using the Calculator

Tips: Enter all values in appropriate units (m³/s for flow, meters for distances). Ensure radial distances are measured from the pumping well center, and r2 > r1 for valid calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between transmissivity and hydraulic conductivity?
A: Hydraulic conductivity is a property of the porous material alone, while transmissivity is the product of hydraulic conductivity and saturated thickness of the aquifer.

Q2: Why use two observation wells instead of one?
A: Using two observation wells eliminates the need to estimate aquifer storage properties and provides more reliable transmissivity calculations.

Q3: What are typical transmissivity values for different aquifers?
A: Transmissivity values range from less than 1 m²/day for tight formations to over 1000 m²/day for highly productive aquifers like gravel or fractured rock.

Q4: When is this formula applicable?
A: This formula applies to steady-state flow in confined aquifers with fully penetrating wells and homogeneous, isotropic aquifer properties.

Q5: What limitations does this method have?
A: The method assumes ideal conditions and may not accurately represent aquifers with heterogeneity, boundary effects, or unconfined conditions.