Drawdown At Well Given Confined Aquifer Discharge Calculator

Formula Used:

\[ Stw = \frac{Q}{\frac{2 \pi KWH \cdot bp}{\ln\left(\frac{Rw}{r}\right)}} \]

Discharge (Q):

m³/s

Coefficient of Permeability (KWH):

m/s

Aquifer Thickness During Pumping (bp):

Radius of Influence (Rw):

Radius of Well (r):

Total Drawdown in Well (Stw):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is Drawdown in Well Hydraulics?

Total Drawdown in Well in Well Hydraulics is defined as the reduction in hydraulic head observed at a well in an aquifer, typically due to pumping a well as part of an aquifer test or well test. It represents the difference between the static water level and the pumping water level.

2. How Does the Calculator Work?

The calculator uses the confined aquifer drawdown formula:

\[ Stw = \frac{Q}{\frac{2 \pi KWH \cdot bp}{\ln\left(\frac{Rw}{r}\right)}} \]

Where:

\( Stw \) — Total Drawdown in Well (m)
\( Q \) — Discharge rate (m³/s)
\( KWH \) — Coefficient of Permeability (m/s)
\( bp \) — Aquifer Thickness During Pumping (m)
\( Rw \) — Radius of Influence (m)
\( r \) — Radius of Well (m)
\( \pi \) — Mathematical constant pi (≈3.14159)
\( \ln \) — Natural logarithm function

Explanation: This formula calculates the drawdown in a confined aquifer based on the aquifer properties and pumping conditions.

3. Importance of Drawdown Calculation

Details: Accurate drawdown calculation is crucial for designing well systems, determining sustainable pumping rates, assessing aquifer characteristics, and managing groundwater resources effectively.

4. Using the Calculator

Tips: Enter all values in appropriate units. Ensure discharge is in m³/s, permeability in m/s, and all distance measurements in meters. All values must be positive and non-zero.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between confined and unconfined aquifers?
A: Confined aquifers are bounded above and below by impermeable layers, while unconfined aquifers have a water table that serves as the upper boundary.

Q2: How is coefficient of permeability determined?
A: It is typically determined through pumping tests, laboratory tests, or estimated from soil characteristics and empirical relationships.

Q3: What factors affect the radius of influence?
A: Pumping rate, aquifer properties, duration of pumping, and boundary conditions all influence the radius of influence.

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

Q5: What are the limitations of this approach?
A: The formula assumes ideal conditions and may not account for aquifer heterogeneity, partial penetration, or transient effects.