- 2075 Baisakh · 1 mark
Formation of an artesian well
Short answer
An artesian well is formed by a confined aquifer: a permeable stratum between impervious beds tilted so recharge area is at higher elevation. Water under pressure rises in a well; if piezometric surface is above ground, it flows freely.
How is an artesian well (aquifer) formed?
An artesian well is formed when a permeable aquifer is confined between two impermeable beds and tilted so that its recharge area lies at a higher level than the well.
Conditions:
- Inclined or synclinal (basin-shaped) permeable bed such as sandstone or sand.
- Impermeable beds (clay, shale) above and below.
- Outcrop of the aquifer at higher elevation where rain or river water enters (recharge).
- Water flows down-dip and gets pressure from the weight of water in the higher part.
When a well is drilled through the upper confining bed, water rises above the aquifer top because of the pressure. If the piezometric surface is above the ground level, water flows out freely without pumping.
recharge area (outcrop) flowing well
high ground | ^ ^
___.........piezometric surface.|..
/ ___________clay_____________ | __ ground
/ ===========sand aquifer======|====
/ ___________clay______________
✓ Answer checked by Claude Opus 5.5 (high effort)
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