Question Bank • QB_IDE_EXP_064 NAT • 2 Marks

Section 5: Irrigation and Drainage Engineering

Groundwater Hydrology

Subtopic: Steady and unsteady flow in confined and unconfined aquifers

Question Statement:

A fully penetrating well pumps water from a confined aquifer of transmissivity $T = 400\text{ m}^2/\text{day}$ at a steady rate of $Q = 1000\text{ m}^3/\text{day}$. Two observation piezometers are located at radial distances $r_1 = 10\text{ m}$ and $r_2 = 50\text{ m}$. Calculate the drawdown difference $(s_1 - s_2)$ in $\text{meters}$. (Take $\pi = 3.1416$)

Answer Key:

0.64

Step-by-Step Solution & Explanation

$\ln\left(\frac{r_2}{r_1}\right) = \ln\left(\frac{50}{10}\right) = \ln(5) \approx 1.6094$ $s_1 - s_2 = \frac{1000}{2 \times 3.1416 \times 400} \times 1.6094 = \frac{1609.4}{2513.28} \approx 0.6403\text{ m}$
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