A tubewell in a confined aquifer has diameter 0.30 m. For a certain yield, radius of influence is 400 m. All conditions remaining the same, if the diameter of the well is doubled, the percentage increase in yield is
Options:
(A) 9.28
(B) 9.63
(C) 10.00
(D) 10.23
Official Answer Key:
B
Step-by-Step Solution & Explanation
For a confined aquifer well (Thiem equation), Q ∝ 1/ln(R/r_w). r_w1 = 0.15 m, r_w2 = 0.30 m, R = 400 m. Q₁ ∝ 1/ln(400/0.15) = 1/7.888 = 0.12677. Q₂ ∝ 1/ln(400/0.30) = 1/7.195 = 0.13898. % increase = (0.13898−0.12677)/0.12677 × 100 = 9.63%.
Section 6 — Agricultural Process Engineering
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