Question

Consider the following statement for groundwater flow
• The water in confined aquifers is having pressure greater than atmospheric pressure.
• The unconfined aquifer is also known as water table aquifer.
• The unconsolidated type of formation have secondary porosity.
• The perched aquifer is a type of unconfined aquifer.
• Hydraulic conductivity has the dimension of velocity. Choose the correct answer from the options given below:

• A. A, B, C, D Only
• B. A, B, D, E Only
• C. B, C, D, E Only
• D. A, C, D, E Only

Hint:

Important groundwater facts:
• Confined aquifer \(\rightarrow\) pressure greater than atmospheric
• Unconfined aquifer \(\rightarrow\) water table aquifer
• Unconsolidated formations \(\rightarrow\) primary porosity
• Hydraulic conductivity dimension: \[ LT^{-1} \] Memory Trick: \[ \boxed{ \text{“Confined-pressure, Unconfined-water table”} } \]

Answer 1

The Correct Option is B

Concept: Groundwater occurs below the earth’s surface within pores and fractures of soil and rock formations. These formations are called aquifers when they can store and transmit water. Groundwater hydrology involves the study of:
• Aquifer types
• Groundwater movement
• Hydraulic conductivity
• Porosity
• Subsurface flow behavior The question requires checking the correctness of individual groundwater statements.

Step 1: Analyzing Statement A. Statement A says: \[ \text{“The water in confined aquifers is having pressure greater than atmospheric pressure.”} \] This statement is correct. A confined aquifer is bounded above and below by impermeable or relatively impermeable layers. Water inside confined aquifers exists under pressure greater than atmospheric pressure. Because of this pressure:
• Water may rise in wells above the aquifer level
• Artesian conditions may occur Hence: \[ \boxed{\text{Statement A is correct}} \]

Step 2: Analyzing Statement B. Statement B says: \[ \text{“The unconfined aquifer is also known as water table aquifer.”} \] This statement is correct. In an unconfined aquifer:
• Upper boundary is the water table
• Water pressure equals atmospheric pressure at the water table Hence unconfined aquifers are commonly called: \[ \boxed{\text{Water table aquifers}} \] Therefore: \[ \boxed{\text{Statement B is correct}} \]

Step 3: Analyzing Statement C. Statement C says: \[ \text{“The unconsolidated type of formation have secondary porosity.”} \] This statement is incorrect. Unconsolidated formations such as:
• Sand
• Gravel
• Alluvium mainly possess: \[ \boxed{\text{Primary porosity}} \] Secondary porosity develops because of:
• Fractures
• Joints
• Solution cavities and is generally associated with consolidated rocks. Hence: \[ \boxed{\text{Statement C is incorrect}} \]

Step 4: Analyzing Statement D. Statement D says: \[ \text{“The perched aquifer is a type of unconfined aquifer.”} \] This statement is correct. A perched aquifer forms when groundwater accumulates above a local impermeable layer located above the main water table. Since it possesses a local water table exposed to atmospheric pressure: \[ \boxed{\text{It behaves as an unconfined aquifer}} \] Therefore: \[ \boxed{\text{Statement D is correct}} \]

Step 5: Analyzing Statement E. Statement E says: \[ \text{“Hydraulic conductivity has the dimension of velocity.”} \] This statement is correct. Hydraulic conductivity \(K\) has dimensions: \[ [K] = LT^{-1} \] which is the same as velocity. Examples: \[ m/s,\quad cm/s \] Hence: \[ \boxed{\text{Statement E is correct}} \]

Step 6: Identifying the correct combination. Correct statements are: \[ A,\; B,\; D,\; E \] Incorrect statement: \[ C \] Thus the correct option is: \[ \boxed{ (B)\ A,\; B,\; D,\; E\ Only } \] Final Conclusion: The correct groundwater statements are: \[ A,\; B,\; D,\; E \] Hence the correct answer is: \[ \boxed{(B)\ A,\; B,\; D,\; E\ Only} \]