Consider the following statements: 1. When two wells operate simultaneously in the same aquifer, their cones of depression may overlap. 2. Increasing well diameter significantly increases the discharge of a well for the same aquifer conditions. 3. Storage coefficient of a confined aquifer is typically much larger than that of an unconfined aquifer. Which of the statements given above is/are correct?
- A1 onlyCorrect
- B1 and 2 only
- C2 and 3 only
- DAll of the above
Solution
Concept
Well Hydraulics and Aquifer Properties
Formula
N/A
Step-by-step solution
1. Review the given statements regarding well hydraulics and aquifer properties. 2. Identify that Statement 1 is correct, while Statements 2 and 3 are incorrect based on well discharge and storage coefficient principles. 3. Select Option (a) as the correct choice.
Explanation
Statement 1 is correct because when two nearby wells pump water at the same time, their water-level lowering zones (cones of depression) can overlap and interfere with each other. Statement 2 is false because doubling or increasing a well's diameter results in only a very small percentage increase in water yield. Statement 3 is false because unconfined aquifers have a much higher storage coefficient (specific yield) than confined aquifers.
Shortcut
To remember key well hydraulics rules, use the mnemonic "OVER-LOG-UNCONFINED": - Overlap: Nearby pumping wells interfere and overlap their cones of depression - Logarithmic Yield: Discharge depends on log(R/r), so increasing diameter gives only a minimal increase in yield - Unconfined is Greater: Unconfined aquifers have much higher storage coefficients (specific yield) than confined aquifers
Common mistake
A common mistake is selecting Option B or D by assuming that doubling or increasing a well's diameter significantly increases its yield; in reality, discharge depends logarithmically on the well radius, so increasing the diameter results in only a minimal increase in yield. Another frequent mistake is believing that confined aquifers have a higher storage coefficient than unconfined aquifers, whereas unconfined aquifers release far more water per unit area due to gravity drainage (specific yield).
Correct answer: A) 1 only