1. What is Change in Drawdown?

Change in Drawdown is defined as the difference in hydraulic head observed at two wells in an aquifer system. It represents the variation in water level reduction between different monitoring points, typically due to pumping activities or natural aquifer dynamics.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( \Delta d \) — Change in Drawdown (m)
• \( st \) — Total Drawdown in Well (m)
• \( Fu \) — Chow's Function (dimensionless)

Explanation: This formula calculates the change in drawdown by dividing the total drawdown observed at a well by Chow's function, which is a constant parameter specific to the aquifer conditions and well configuration.

3. Importance of Change in Drawdown Calculation

Details: Calculating change in drawdown is crucial for understanding aquifer response to pumping, determining well interference effects, assessing groundwater resource sustainability, and designing efficient well field layouts. It helps hydrogeologists evaluate the impact of extraction on surrounding water levels.

4. Using the Calculator

Tips: Enter the total drawdown in meters and Chow's function value. Both values must be positive numbers. The calculator will compute the change in drawdown between monitoring points.

5. Frequently Asked Questions (FAQ)

Q1: What is Chow's Function?
A: Chow's Function is a dimensionless constant that accounts for specific aquifer characteristics and well configuration. It is derived from analytical solutions to groundwater flow equations and varies depending on the hydrogeological setting.

Q2: How is total drawdown measured?
A: Total drawdown is typically measured using pressure transducers or manual water level measurements in monitoring wells before, during, and after pumping tests to record the maximum reduction in hydraulic head.

Q3: What factors influence change in drawdown?
A: Change in drawdown is influenced by aquifer properties (transmissivity, storage coefficient), pumping rate, duration of pumping, distance between wells, and boundary conditions of the aquifer system.

Q4: When is this calculation most useful?
A: This calculation is particularly useful during aquifer performance tests, well interference studies, and when designing multiple well systems to minimize mutual interference between extraction points.

Q5: Are there limitations to this approach?
A: This approach assumes ideal aquifer conditions and may need modification for heterogeneous aquifers, fractured rock systems, or complex boundary conditions where more sophisticated numerical modeling may be required.