Drawdown In Well 2 Given Aquifer Constant Calculator

Formula Used:

\[ s_2 = s_1 - \frac{Q \cdot \log_{10}\left(\frac{r_2}{r_1}\right)}{2.72 \cdot T} \]

Drawdown in well 1 (s₁):

Discharge (Q):

m³/s

Radial Distance at Observation Well 2 (r₂):

Radial Distance at Observation Well 1 (r₁):

Aquifer Constant (T):

Drawdown in well 2 (s₂):

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1. What is the Drawdown Calculation Formula?

The drawdown calculation formula estimates the water level decline in an observation well based on known parameters from another well. This is essential in hydrogeology for analyzing aquifer characteristics and predicting water level changes.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ s_2 = s_1 - \frac{Q \cdot \log_{10}\left(\frac{r_2}{r_1}\right)}{2.72 \cdot T} \]

Where:

\( s_2 \) — Drawdown in well 2 (m)
\( s_1 \) — Drawdown in well 1 (m)
\( Q \) — Discharge rate (m³/s)
\( r_2 \) — Radial distance at observation well 2 (m)
\( r_1 \) — Radial distance at observation well 1 (m)
\( T \) — Aquifer constant (coefficient of transmissibility)

Explanation: The formula calculates the drawdown in a second observation well based on known drawdown in the first well, accounting for discharge rate, radial distances, and aquifer transmissibility.

3. Importance of Drawdown Calculation

Details: Accurate drawdown calculation is crucial for groundwater resource management, well field design, contamination studies, and predicting the impact of pumping on aquifer systems.

4. Using the Calculator

Tips: Enter all values in appropriate units. Drawdown values should be positive, distances must be greater than zero, and discharge and aquifer constant must be positive values.

5. Frequently Asked Questions (FAQ)

Q1: What is the significance of the logarithmic term?
A: The logarithmic term accounts for the radial flow pattern in confined aquifers, where drawdown decreases logarithmically with distance from the pumping well.

Q2: When is this formula applicable?
A: This formula is typically used for confined aquifers under steady-state conditions with fully penetrating wells.

Q3: What are typical units for aquifer constant?
A: The aquifer constant (transmissivity) is typically expressed in m²/day or m²/s, representing the rate at which water flows through a unit width of aquifer under a unit hydraulic gradient.

Q4: Can this formula be used for unconfined aquifers?
A: For unconfined aquifers, modifications are needed to account for the decreasing saturated thickness with drawdown.

Q5: What if the calculated s₂ is negative?
A: A negative s₂ value would indicate a water level rise rather than drawdown, which might occur in specific hydrogeological conditions or if input values are incorrect.