Specific Capacity of Open Well Calculator

Specific Capacity Formula:

\[ Specific\ Capacity = \frac{1}{Time} \times \ln\left(\frac{Depression\ Head\ 1}{Depression\ Head\ 2}\right) \]

Specific Capacity (KA):

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1. What is Specific Capacity of Open Well?

Specific Capacity of an open well is a measure of the well's productivity, representing the discharge per unit drawdown. It indicates how much water can be extracted from the well for a given drop in water level.

2. How Does the Calculator Work?

The calculator uses the Specific Capacity formula:

\[ Specific\ Capacity = \frac{1}{Time} \times \ln\left(\frac{Depression\ Head\ 1}{Depression\ Head\ 2}\right) \]

Where:

\( Time \) — Time duration (seconds)
\( Depression\ Head\ 1 \) — Initial difference between water table and water level in well (meters)
\( Depression\ Head\ 2 \) — Final difference between water table and water level in well (meters)
\( \ln \) — Natural logarithm (base e)

Explanation: The formula calculates the rate at which water can be extracted from the well per unit drawdown, which is an important parameter in well hydraulics.

3. Importance of Specific Capacity Calculation

Details: Specific capacity is crucial for well design, determining well efficiency, assessing aquifer characteristics, and planning sustainable water extraction rates.

4. Using the Calculator

Tips: Enter time in seconds, depression heads in meters. All values must be positive numbers. Depression Head 1 should be greater than Depression Head 2 for meaningful results.

5. Frequently Asked Questions (FAQ)

Q1: What is a good specific capacity value?
A: Higher specific capacity values indicate more productive wells. Values vary widely depending on aquifer characteristics, but generally values above 0.1 m²/s are considered good.

Q2: How does specific capacity relate to transmissivity?
A: Specific capacity is directly related to the transmissivity of the aquifer. Higher transmissivity generally results in higher specific capacity.

Q3: Why use natural logarithm in the formula?
A: The natural logarithm (base e) is used because it arises naturally from the solution of the differential equations describing groundwater flow to wells.

Q4: Can this formula be used for confined aquifers?
A: This specific formula is designed for open wells in unconfined aquifers. Different equations apply to confined aquifers.

Q5: What factors affect specific capacity?
A: Specific capacity is affected by aquifer properties, well construction, degree of well development, and any well damage or clogging over time.