Question

Pumping and extraction of groundwater from an unconfined aquifer resulted in a uniform drop of water table by 40 m over an area of 1 km². If the porosity of the aquifer is 35% and specific retention is 15%, the volume of water (in m³) pumped out from the affected area is __________ \times 10^6 m³. (In integer)

Hint:

The volume of water pumped from an aquifer can be calculated using the drop in the water table, the area of extraction, and the sum of the porosity and specific retention.

Answer 1

Step 1: Understanding the given information.
- The drop in the water table is \( 40 \, \text{m} \).
- The area of extraction is \( 1 \, \text{km}^2 = 10^6 \, \text{m}^2 \).
- The porosity of the aquifer is \( 35% = 0.35 \).
- The specific retention is \( 15% = 0.15 \).
Step 2: Calculate the volume of water extracted.
The volume of water that is extracted is given by: \[ \text{Volume} = \text{Area} \times \text{Drop in water table} \times (\text{Porosity} + \text{Specific Retention}) \] Substitute the given values: \[ \text{Volume} = 10^6 \, \text{m}^2 \times 40 \, \text{m} \times (0.35 + 0.15) \] \[ \text{Volume} = 10^6 \times 40 \times 0.50 = 20 \times 10^6 \, \text{m}^3 \] Step 3: Final answer.
The volume of water pumped out is: \[ \boxed{20} \times 10^6 \, \text{m}^3 \]