Irrigation and Drainage Engineering · Groundwater Hydrology · 1 mark · Numerical answer
A fully penetrating 300 mm diameter well pumps 1200 m³/day from a confined aquifer with transmissivity 1000 m²/day. Radius of influence is 400 m. Find steady well drawdown in m, to two decimals. Use π=3.14.
Thiem’s confined-flow relation gives $s=Q\ln(R/r_w)/(2\pi T)$. With $r_w=.15$ m, $s=1200\ln(400/.15)/(2(3.14)(1000))=1.50737$ m, or **1.51 m**. The well radius, not diameter, enters the logarithm.
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