Storage Coefficient For Inconsistent Units From Distance Drawdown Graphs Calculator

Storage Coefficient Formula:

\[ S = \frac{T \times s_t}{640 \times r_o^2} \]

Transmissivity (T):

m²/s

Total Drawdown (sₜ):

Distance from Pumping Well to Point Intersection (rₒ):

Storage Coefficient (S):

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1. What is the Storage Coefficient?

The Storage Coefficient is referred as volume of water released from storage per unit decline in hydraulic head in the aquifer, per unit area of the aquifer. It is a dimensionless parameter that indicates the amount of water an aquifer releases from or takes into storage per unit surface area per unit change in head.

2. How Does the Calculator Work?

The calculator uses the Storage Coefficient formula:

\[ S = \frac{T \times s_t}{640 \times r_o^2} \]

Where:

\( S \) — Storage Coefficient (dimensionless)
\( T \) — Transmissivity (m²/s)
\( s_t \) — Total Drawdown (m)
\( r_o \) — Distance from Pumping Well to Point Intersection (m)

Explanation: This formula calculates the storage coefficient using transmissivity, total drawdown, and distance from the pumping well to the point intersection with the zero-drawdown line.

3. Importance of Storage Coefficient Calculation

Details: The storage coefficient is a critical parameter in groundwater hydrology that helps determine an aquifer's ability to store and transmit water. It is essential for modeling groundwater flow, predicting aquifer response to pumping, and managing water resources effectively.

4. Using the Calculator

Tips: Enter transmissivity in m²/s, total drawdown in meters, and distance from pumping well to point intersection in meters. All values must be positive numbers greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical range of storage coefficient values?
A: For confined aquifers, storage coefficients typically range from 0.00001 to 0.001. For unconfined aquifers, values are much higher, typically between 0.1 and 0.3.

Q2: How does storage coefficient differ from specific yield?
A: Storage coefficient applies to confined aquifers and represents elastic storage, while specific yield applies to unconfined aquifers and represents water that drains by gravity.

Q3: Why is the constant 640 used in the formula?
A: The constant 640 is a conversion factor that accounts for the specific units used in this particular formulation of the distance-drawdown method.

Q4: What are the limitations of this calculation method?
A: This method assumes ideal aquifer conditions, homogeneous and isotropic properties, and may not be accurate for complex aquifer systems or near boundary conditions.

Q5: How is the point intersection determined?
A: The point intersection is found by extending the straight-line portion of the distance-drawdown graph to intersect with the zero-drawdown line.