During the recuperation test of a 4.0 m open well a recuperation of the depression head from 2.5 m to 1.25 m was found to take place in 90 minutes. Determine specific capacity per unit well area. Also determine yield of well for safe drawdown of 2.5 m.

Given Data,

Time of recuperator (Tr) = 90 min. = 90/60 hr = 1.5 hr

Initial depression head (H1) = 2.5 m

Final description head (H2) = 1.25 m

Area (A) = /4 ∗ d2 = /4 ∗ (4)2 = 12.567 m2

1. Specific capacity per unit well area

Ks = (1/Tr) ∙ loge(H1/H2)

Ks = (1/1.5) ∙ loge(2.5/1.25)

Ks = 0.462 h-1

2. Yield of well for safe drawdown of 2.5 m

Q = Ks ∙ A ∙ H

Q = 0.462 ∗ 12.567 ∗ 2.5

Q = 14.52 m3/hr

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